Functional materials discovery using energy-structure-function maps

NASA Astrophysics Data System (ADS)

Pulido, Angeles; Chen, Linjiang; Kaczorowski, Tomasz; Holden, Daniel; Little, Marc A.; Chong, Samantha Y.; Slater, Benjamin J.; McMahon, David P.; Bonillo, Baltasar; Stackhouse, Chloe J.; Stephenson, Andrew; Kane, Christopher M.; Clowes, Rob; Hasell, Tom; Cooper, Andrew I.; Day, Graeme M.

2017-03-01

Molecular crystals cannot be designed in the same manner as macroscopic objects, because they do not assemble according to simple, intuitive rules. Their structures result from the balance of many weak interactions, rather than from the strong and predictable bonding patterns found in metal-organic frameworks and covalent organic frameworks. Hence, design strategies that assume a topology or other structural blueprint will often fail. Here we combine computational crystal structure prediction and property prediction to build energy-structure-function maps that describe the possible structures and properties that are available to a candidate molecule. Using these maps, we identify a highly porous solid, which has the lowest density reported for a molecular crystal so far. Both the structure of the crystal and its physical properties, such as methane storage capacity and guest-molecule selectivity, are predicted using the molecular structure as the only input. More generally, energy-structure-function maps could be used to guide the experimental discovery of materials with any target function that can be calculated from predicted crystal structures, such as electronic structure or mechanical properties.

Functional materials discovery using energy-structure-function maps.

PubMed

Pulido, Angeles; Chen, Linjiang; Kaczorowski, Tomasz; Holden, Daniel; Little, Marc A; Chong, Samantha Y; Slater, Benjamin J; McMahon, David P; Bonillo, Baltasar; Stackhouse, Chloe J; Stephenson, Andrew; Kane, Christopher M; Clowes, Rob; Hasell, Tom; Cooper, Andrew I; Day, Graeme M

2017-03-30

Molecular crystals cannot be designed in the same manner as macroscopic objects, because they do not assemble according to simple, intuitive rules. Their structures result from the balance of many weak interactions, rather than from the strong and predictable bonding patterns found in metal-organic frameworks and covalent organic frameworks. Hence, design strategies that assume a topology or other structural blueprint will often fail. Here we combine computational crystal structure prediction and property prediction to build energy-structure-function maps that describe the possible structures and properties that are available to a candidate molecule. Using these maps, we identify a highly porous solid, which has the lowest density reported for a molecular crystal so far. Both the structure of the crystal and its physical properties, such as methane storage capacity and guest-molecule selectivity, are predicted using the molecular structure as the only input. More generally, energy-structure-function maps could be used to guide the experimental discovery of materials with any target function that can be calculated from predicted crystal structures, such as electronic structure or mechanical properties.

The strength of a calcified tissue depends in part on the molecular structure and organization of its constituent mineral crystals in their organic matrix

NASA Technical Reports Server (NTRS)

Landis, W. J.

1995-01-01

High-voltage electron-microscopic tomographic (3D) studies of the ultrastructural interaction between mineral and organic matrix in a variety of calcified tissues reveal different crystal structural and organizational features in association with their respective organic matrices. In brittle or weak pathologic or ectopic calcifications, including examples of osteogenesis imperfecta, calciphylaxis, calcergy, and dermatomyositis, hydroxyapatite crystals occur in various sizes and shapes and are oriented and aligned with respect to collagen in a manner which is distinct from that found in normal calcified tissues. A model of collagen-mineral interaction is proposed which may account for the observed crystal structures and organization. The results indicate that the ultimate strength, support, and other mechanical properties provided by a calcified tissue are dependent in part upon the molecular structure and arrangement of its constituent mineral crystals within their organic matrix.

Highly Efficient and Simple Route to Synthesize N-(4-Acetylphenyl)-4-chlorobenzenesulfonamide and Its Crystal Structure

NASA Astrophysics Data System (ADS)

Kobkeatthawin, T.; Chantrapromma, S.; Chidan Kumar, C. S.; Fun, H.-K.

2017-12-01

The one-pot synthesis of N-(4-acetylphenyl)-4-chlorobenzenesulfonamide under base conditions is carried out. The present method offers several advantages such as excellent yields, short reaction times and high purity. The chemical structure was elucidated using 1H-NMR, FT-IR and UV-Vis spectroscopy. The crystal structure of the substance was determined by single crystal X-ray structure analysis. The molecule is in a V-shape. The two substituted benzene rings make the dihedral angle of 84.31(9)°. In the crystal packing, the molecules are linked by N-H···O and C-H···O hydrogen bonds into double chains along the b-axis. The crystal is further stabilized by weak C-H···O, C-Cl···π and π···π interactions.

Data on crystal organization in the structure of the Fab fragment from the NIST reference antibody, RM 8671.

PubMed

Gallagher, D T; Karageorgos, I; Hudgens, J W; Galvin, C V

2018-02-01

The reported data describe the crystallization, crystal packing, structure determination and twinning of the unliganded Fab (antigen-binding fragment) from the NISTmAb (standard reference material 8671). The raw atomic coordinates are available as Protein Data Bank structure 5K8A and biological aspects are described in the article, (Karageorgos et al., 2017) [1]. Crystal data show that the packing is unique, and show the basis for the crystal's twinned growth. Twinning is a common and often serious problem in protein structure determination by x-ray crystallography [2]. In the present case the twinning is due to a small deviation (about 0.3 nm) from 4-fold symmetry in the primary intermolecular interface. The deviation produces pseudosymmetry, generating slightly different conformations of the protein, and alternating strong and weak forms of key packing interfaces throughout the lattice.

The strength of a calcified tissue depends in part on the molecular structure and organization of its constituent mineral crystals in their organic matrix.

PubMed

Landis, W J

1995-05-01

High-voltage electron-microscopic tomographic (3D) studies of the ultrastructural interaction between mineral and organic matrix in a variety of calcified tissues reveal different crystal structural and organizational features in association with their respective organic matrices. In brittle or weak pathologic or ectopic calcifications, including examples of osteogenesis imperfecta, calciphylaxis, calcergy, and dermatomyositis, hydroxyapatite crystals occur in various sizes and shapes and are oriented and aligned with respect to collagen in a manner which is distinct from that found in normal calcified tissues. A model of collagen-mineral interaction is proposed which may account for the observed crystal structures and organization. The results indicate that the ultimate strength, support, and other mechanical properties provided by a calcified tissue are dependent in part upon the molecular structure and arrangement of its constituent mineral crystals within their organic matrix.

Crystal structure of 1-methyl-3-([2,2-dimethyl-4,6-dioxo-1,3-dioxane-5-ylidene]methyl)urea

DOE Office of Scientific and Technical Information (OSTI.GOV)

Habibi, A., E-mail: habibi@khu.ac.ir; Ghorbani, H. S.; Bruno, G.

2013-12-15

The crystal structure of 1-Methyl-3-([2,2-dimethyl-4,6-dioxo-1,3-dioxane-5-ylidene]methyl)urea (C{sub 9}H{sub 12}N{sub 2}O{sub 5}) has been determined by single crystal X-ray diffraction analysis. The crystals are monoclinic, a = 5.3179(2), b = 18.6394(6), c =10.8124(3) Å, β = 100.015(2)°, Z = 4, sp. gr. P2{sub 1}/c, R = 0.0381 for 2537 reflections with I > 2σ(I). Except for C(CH{sub 3}){sub 2} group, the molecule is planar. The structure is stabilized by inter- and intramolecular N-H...O hydrogen bonds and weak C-H...O interactions.

Crystal structure of [Eu(CyMe4-BTBP)2κ2O,O'-(NO3)](NO3)2·n-C8H17OH and its structure in 1-octanol solution.

PubMed

Lundberg, Daniel; Persson, Ingmar; Ekberg, Christian

2013-03-21

The structure of the [Eu(CyMe(4)-BTBP)(2)(NO(3))(n)]((3-n)+) complex in 1-octanol solution and solid state has been determined by EXAFS and X-ray crystallography. The crystal structure shows that 1-octanol binds only to the europium(III)-coordinated BTBP molecules through weak van der Waals forces, making it the first indication of the role of the extraction solvent.

Hirshfeld surface analyses and crystal structures of supramolecular self-assembly thiourea derivatives directed by non-covalent interactions

NASA Astrophysics Data System (ADS)

Gumus, Ilkay; Solmaz, Ummuhan; Binzet, Gun; Keskin, Ebru; Arslan, Birdal; Arslan, Hakan

2018-04-01

The novel N-(bis(3,5-dimethoxybenzyl)carbamothioyl)-4-R-benzamide (R: H, Cl, CH3 and OCH3) compounds have been synthesized and characterized by FT-IR, 1H NMR and 13C NMR spectroscopy. Their crystal structures were also determined by single-crystal X-ray diffraction studies. Hirshfeld surfaces analysis and their associated two dimensional fingerprint plots of compounds were used as theoretical approach to assess driving force for crystal structure formation via the intermolecular interactions in the crystal lattices of synthesized compounds. The study of X-ray single crystal diffraction and Hirshfeld surfaces analysis of the prepared compounds shows that hydrogen bonding and other weaker interactions such as Nsbnd H⋯S, weak Csbnd H⋯S, Csbnd H⋯O, Csbnd H⋯N and Csbnd H···π intermolecular interactions and π-π stacking, among molecules of synthesized compounds participate in a cooperative way to stabilize the supramolecular structures.

Crystal structure and hydrogen-bonding patterns in 5-fluoro-cytosinium picrate.

PubMed

Mohana, Marimuthu; Thomas Muthiah, Packianathan; McMillen, Colin D

2017-03-01

In the crystal structure of the title compound, 5-fluoro-cytosinium picrate, C 4 H 5 FN 3 O + ·C 6 H 2 N 3 O 7 - , one N heteroatom of the 5-fluoro-cytosine (5FC) ring is protonated. The 5FC ring forms a dihedral angle of 19.97 (11)° with the ring of the picrate (PA - ) anion. In the crystal, the 5FC + cation inter-acts with the PA - anion through three-centre N-H⋯O hydrogen bonds, forming two conjoined rings having R 2 1 (6) and R 1 2 (6) motifs, and is extended by N-H⋯O hydrogen bonds and C-H⋯O inter-actions into a two-dimensional sheet structure lying parallel to (001). Also present in the crystal structure are weak C-F⋯π inter-actions.

A hybrid computational-experimental approach for automated crystal structure solution

NASA Astrophysics Data System (ADS)

Meredig, Bryce; Wolverton, C.

2013-02-01

Crystal structure solution from diffraction experiments is one of the most fundamental tasks in materials science, chemistry, physics and geology. Unfortunately, numerous factors render this process labour intensive and error prone. Experimental conditions, such as high pressure or structural metastability, often complicate characterization. Furthermore, many materials of great modern interest, such as batteries and hydrogen storage media, contain light elements such as Li and H that only weakly scatter X-rays. Finally, structural refinements generally require significant human input and intuition, as they rely on good initial guesses for the target structure. To address these many challenges, we demonstrate a new hybrid approach, first-principles-assisted structure solution (FPASS), which combines experimental diffraction data, statistical symmetry information and first-principles-based algorithmic optimization to automatically solve crystal structures. We demonstrate the broad utility of FPASS to clarify four important crystal structure debates: the hydrogen storage candidates MgNH and NH3BH3; Li2O2, relevant to Li-air batteries; and high-pressure silane, SiH4.

7-Meth­oxy­indan-1-one

PubMed Central

Chang, Yuan Jay; Chen, Kew-Yu

2012-01-01

In the title compound, C10H10O2, the 1-indanone unit is essentially planar (r.m.s. deviation = 0.028 Å). In the crystal, molecules are linked via C—H⋯O hydrogen bonds, forming layers lying parallel to the ab plane. This two-dimensional structure is stabilized by a weak C—H⋯π inter­action. A second weak C—H⋯π inter­action links the layers, forming a three-dimensional structure. PMID:23284398

Crystallization-induced emission enhancement: A novel fluorescent Au-Ag bimetallic nanocluster with precise atomic structure

PubMed Central

Chen, Tao; Yang, Sha; Chai, Jinsong; Song, Yongbo; Fan, Jiqiang; Rao, Bo; Sheng, Hongting; Yu, Haizhu; Zhu, Manzhou

2017-01-01

We report the first noble metal nanocluster with a formula of Au4Ag13(DPPM)3(SR)9 exhibiting crystallization-induced emission enhancement (CIEE), where DPPM denotes bis(diphenylphosphino)methane and HSR denotes 2,5-dimethylbenzenethiol. The precise atomic structure is determined by x-ray crystallography. The crystalline state of Au4Ag13 shows strong luminescence at 695 nm, in striking contrast to the weak emission of the amorphous state and hardly any emission in solution phase. The structural analysis and the density functional theory calculations imply that the compact C–H⋯π interactions significantly restrict the intramolecular rotations and vibrations and thus considerably enhance the radiative transitions in the crystalline state. Because the noncovalent interactions can be easily modulated via varying the chemical environments, the CIEE phenomenon might represent a general strategy to amplify the fluorescence from weakly (or even non-) emissive nanoclusters. PMID:28835926

Crystal structure and functional characterization of SF216 from Shigella flexneri.

PubMed

Kim, Ha-Neul; Seok, Seung-Hyeon; Lee, Yoo-Sup; Won, Hyung-Sik; Seo, Min-Duk

2017-11-01

Shigella flexneri is a Gram-negative anaerobic bacterium that causes highly infectious bacterial dysentery in humans. Here, we solved the crystal structure of SF216, a hypothetical protein from the S. flexneri 5a strain M90T, at 1.7 Å resolution. The crystal structure of SF216 represents a homotrimer stabilized by intersubunit interactions and ion-mediated electrostatic interactions. Each subunit consists of three β-strands and five α-helices with the β-β-β-α-α-α-α-α topology. Based on the structural information, we also demonstrate that SF216 shows weak ribonuclease activity by a fluorescence quenching assay. Furthermore, we identify potential druggable pockets (putative hot spots) on the surface of the SF216 structure by computational mapping. © 2017 Federation of European Biochemical Societies.

Crystal structure and hydrogen-bonding patterns in 5-fluoro­cytosinium picrate

PubMed Central

Mohana, Marimuthu; Thomas Muthiah, Packianathan; McMillen, Colin D.

2017-01-01

In the crystal structure of the title compound, 5-fluoro­cytosinium picrate, C4H5FN3O+·C6H2N3O7 −, one N heteroatom of the 5-fluoro­cytosine (5FC) ring is protonated. The 5FC ring forms a dihedral angle of 19.97 (11)° with the ring of the picrate (PA−) anion. In the crystal, the 5FC+ cation inter­acts with the PA− anion through three-centre N—H⋯O hydrogen bonds, forming two conjoined rings having R 2 1(6) and R 1 2(6) motifs, and is extended by N—H⋯O hydrogen bonds and C—H⋯O inter­actions into a two-dimensional sheet structure lying parallel to (001). Also present in the crystal structure are weak C—F⋯π inter­actions. PMID:28316809

Additional evidence from x-ray powder diffraction patterns that icosahedral quasi-crystals of intermetallic compounds are twinned cubic crystals

PubMed Central

Pauling, Linus

1988-01-01

Analysis of the measured values of Q for the weak peaks (small maxima, usually considered to be background fluctuations, “noise”) on the x-ray powder diffraction curves for 17 rapidly quenched alloys leads directly to the conclusion that they are formed by an 820-atom or 1012-atom primitive cubic structure that by icosahedral twinning produces the so-called icosahedral quasi-crystals. PMID:16593948

2-[2-(3-Chloro­phen­yl)hydrazinyl­idene]-1,3-diphenyl­propane-1,3-dione

PubMed Central

Bustos, Carlos; Alvarez-Thon, Luis; Cárcamo, Juan-Guillermo; Ibañez, Andrés; Sánchez, Christian

2011-01-01

The mol­ecular structure of the title compound, C21H15ClN2O2, features one strong intra­molecular N—H⋯O resonance-assisted hydrogen bond (RAHB). In the crystal, mol­ecules form inversion-related dimers via pairs of weak inter­molecular N—H⋯O contacts. These dimers are further stabilized via three weak C—H⋯O contacts, developing the three-dimensional structure. PMID:21754825

Prediction of weak topological insulators in layered semiconductors.

PubMed

Yan, Binghai; Müchler, Lukas; Felser, Claudia

2012-09-14

We report the discovery of weak topological insulators by ab initio calculations in a honeycomb lattice. We propose a structure with an odd number of layers in the primitive unit cell as a prerequisite for forming weak topological insulators. Here, the single-layered KHgSb is the most suitable candidate for its large bulk energy gap of 0.24 eV. Its side surface hosts metallic surface states, forming two anisotropic Dirac cones. Although the stacking of even-layered structures leads to trivial insulators, the structures can host a quantum spin Hall layer with a large bulk gap, if an additional single layer exists as a stacking fault in the crystal. The reported honeycomb compounds can serve as prototypes to aid in the finding of new weak topological insulators in layered small-gap semiconductors.

Crystal structures of (2E)-1-(3-bromo-thio-phen-2-yl)-3-(2-meth-oxy-phen-yl)prop-2-en-1-one and (2E)-1-(3-bromo-thio-phen-2-yl)-3-(3,4-di-meth-oxy-phen-yl)prop-2-en-1-one.

PubMed

Naik, Vasant S; Shettigar, Venkataraya; Berglin, Tyler S; Coburn, Jillian S; Jasinski, Jerry P; Yathirajan, Hemmige S

2015-08-01

In the mol-ecules of the title compounds, (2E)-1-(3-bromo-thio-phen-2-yl)-3-(2-meth-oxy-phen-yl)prop-2-en-1-one, C14H11BrO2S, (I), which crystallizes in the space group P-1 with four independent mol-ecules in the asymmetric unit (Z' = 8), and (2E)-1-(3-bromo-thio-phen-2-yl)-3-(3,4-di-meth-oxy-phen-yl)prop-2-en-1-one, C15H13BrO3S, (II), which crystallizes with Z' = 8 in the space group I2/a, the non-H atoms are nearly coplanar. The mol-ecules of (I) pack with inversion symmetry stacked diagonally along the a-axis direction. Weak C-H⋯Br intra-molecular inter-actions in each of the four mol-ecules in the asymmetric unit are observed. In (II), weak C-H⋯O, bifurcated three-center inter-molecular inter-actions forming dimers along with weak C-H⋯π and π-π stacking inter-actions are observed, linking the mol-ecules into sheets along [001]. A weak C-H⋯Br intra-molecular inter-action is also present. There are no classical hydrogen bonds present in either structure.

DNA Nanotubes for NMR Structure Determination of Membrane Proteins

PubMed Central

Bellot, Gaëtan; McClintock, Mark A.; Chou, James J; Shih, William M.

2013-01-01

Structure determination of integral membrane proteins by solution NMR represents one of the most important challenges of structural biology. A Residual-Dipolar-Coupling-based refinement approach can be used to solve the structure of membrane proteins up to 40 kDa in size, however, a weak-alignment medium that is detergent-resistant is required. Previously, availability of media suitable for weak alignment of membrane proteins was severely limited. We describe here a protocol for robust, large-scale synthesis of detergent-resistant DNA nanotubes that can be assembled into dilute liquid crystals for application as weak-alignment media in solution NMR structure determination of membrane proteins in detergent micelles. The DNA nanotubes are heterodimers of 400nm-long six-helix bundles each self-assembled from a M13-based p7308 scaffold strand and >170 short oligonucleotide staple strands. Compatibility with proteins bearing considerable positive charge as well as modulation of molecular alignment, towards collection of linearly independent restraints, can be introduced by reducing the negative charge of DNA nanotubes via counter ions and small DNA binding molecules. This detergent-resistant liquid-crystal media offers a number of properties conducive for membrane protein alignment, including high-yield production, thermal stability, buffer compatibility, and structural programmability. Production of sufficient nanotubes for 4–5 NMR experiments can be completed in one week by a single individual. PMID:23518667

Structure of the GH1 domain of guanylate kinase-associated protein from Rattus norvegicus

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tong, Junsen; Yang, Huiseon; Eom, Soo Hyun

2014-09-12

Graphical abstract: - Highlights: • The crystal structure of GKAP homology domain 1 (GH1) was determined. • GKAP GH1 is a three-helix bundle connected by short flexible loops. • The predicted helix α4 associates weakly with the helix α3, suggesting dynamic nature of the GH1 domain. - Abstract: Guanylate-kinase-associated protein (GKAP) is a scaffolding protein that links NMDA receptor-PSD-95 to Shank–Homer complexes by protein–protein interactions at the synaptic junction. GKAP family proteins are characterized by the presence of a C-terminal conserved GKAP homology domain 1 (GH1) of unknown structure and function. In this study, crystal structure of the GH1 domainmore » of GKAP from Rattus norvegicus was determined in fusion with an N-terminal maltose-binding protein at 2.0 Å resolution. The structure of GKAP GH1 displays a three-helix bundle connected by short flexible loops. The predicted helix α4 which was not visible in the crystal structure associates weakly with the helix α3 suggesting dynamic nature of the GH1 domain. The strict conservation of GH1 domain across GKAP family members and the lack of a catalytic active site required for enzyme activity imply that the GH1 domain might serve as a protein–protein interaction module for the synaptic protein clustering.« less

(E)-1,2-Bis(4-methyl­phen­yl)ethane-1,2-dione

PubMed Central

Fun, Hoong-Kun; Kia, Reza

2008-01-01

In the mol­ecule of the title compound, C16H14O2, a substituted benzil, the dicarbonyl unit has an s-trans conformation. This conformation is substanti­ated by the O—C—C—O torsion angle of 108.16 (15)°. The dihedral angle between the two aromatic rings is 72.00 (6)°. In the crystal structure, neighbouring mol­ecules are linked together by weak inter­molecular C—H⋯O hydrogen bonds and weak inter­molecular C—H⋯π inter­actions. In addition, the crystal structure is further stabilized by inter­molecular π–π inter­actions with centroid–centroid distances in the range 3.6000 (8)–3.8341 (8) Å. PMID:21203307

Mechanochemical synthesis of N-salicylidene­aniline: thermosalient effect of polymorphic crystals

PubMed Central

Mittapalli, Sudhir; Sravanakumar Perumalla, D.

2017-01-01

Polymorphs of the dichloro derivative of N-salicylideneaniline exhibit mechanical responses such as jumping (Forms I and III) and exploding (Form II) in its three polymorphs. The molecules are connected via the amide N—H⋯O dimer synthon and C—Cl⋯O halogen bond in the three crystal structures. A fourth high-temperature Form IV was confirmed by variable-temperature single-crystal X-ray diffraction at 180°C. The behaviour of jumping exhibited by the polymorphic crystals of Forms I and III is due to the layered sheet morphology and the transmission of thermal stress in a single direction, compared with the corrugated sheet structure of Form II such that heat dissipation is more isotropic causing blasting. The role of weak C—Cl⋯O interactions in the thermal response of molecular crystals is discussed. PMID:28512571

Controlling Chirality of Entropic Crystals

NASA Astrophysics Data System (ADS)

Damasceno, Pablo F.; Karas, Andrew S.; Schultz, Benjamin A.; Engel, Michael; Glotzer, Sharon C.

2015-10-01

Colloidal crystal structures with complexity and diversity rivaling atomic and molecular crystals have been predicted and obtained for hard particles by entropy maximization. However, thus far homochiral colloidal crystals, which are candidates for photonic metamaterials, are absent. Using Monte Carlo simulations we show that chiral polyhedra exhibiting weak directional entropic forces self-assemble either an achiral crystal or a chiral crystal with limited control over the crystal handedness. Building blocks with stronger faceting exhibit higher selectivity and assemble a chiral crystal with handedness uniquely determined by the particle chirality. Tuning the strength of directional entropic forces by means of particle rounding or the use of depletants allows for reconfiguration between achiral and homochiral crystals. We rationalize our findings by quantifying the chirality strength of each particle, both from particle geometry and potential of mean force and torque diagrams.

DNA nanotubes for NMR structure determination of membrane proteins.

PubMed

Bellot, Gaëtan; McClintock, Mark A; Chou, James J; Shih, William M

2013-04-01

Finding a way to determine the structures of integral membrane proteins using solution nuclear magnetic resonance (NMR) spectroscopy has proved to be challenging. A residual-dipolar-coupling-based refinement approach can be used to resolve the structure of membrane proteins up to 40 kDa in size, but to do this you need a weak-alignment medium that is detergent-resistant and it has thus far been difficult to obtain such a medium suitable for weak alignment of membrane proteins. We describe here a protocol for robust, large-scale synthesis of detergent-resistant DNA nanotubes that can be assembled into dilute liquid crystals for application as weak-alignment media in solution NMR structure determination of membrane proteins in detergent micelles. The DNA nanotubes are heterodimers of 400-nm-long six-helix bundles, each self-assembled from a M13-based p7308 scaffold strand and >170 short oligonucleotide staple strands. Compatibility with proteins bearing considerable positive charge as well as modulation of molecular alignment, toward collection of linearly independent restraints, can be introduced by reducing the negative charge of DNA nanotubes using counter ions and small DNA-binding molecules. This detergent-resistant liquid-crystal medium offers a number of properties conducive for membrane protein alignment, including high-yield production, thermal stability, buffer compatibility and structural programmability. Production of sufficient nanotubes for four or five NMR experiments can be completed in 1 week by a single individual.

Tailoring the structures and photonic properties of low-dimensional organic materials by crystal engineering.

PubMed

Li, Qing; Jin, Wang; Chu, Manman; Zhang, Wei; Gu, Jianmin; Shahid, Bilal; Chen, Aibing; Yu, Yifeng; Qiao, Shanlin; Zhao, Yong Sheng

2018-03-08

Low-dimensional organic materials have given rise to tremendous interest in optoelectronic applications, owing to their controllable photonic properties. However, the controlled-synthesis approaches for organic nano-/micro-architectures are very difficult to attain, because the weak interaction (van der Waals force) between the organic molecules cannot dominate the kinetic process of crystal growth. We report a simple method, which involves selective adhesion to the organic crystal plane by hydrogen-bonding interaction for modulating the crystal growth process, which leads either to the self-assembly of one organic molecule into two-dimensional (2D) microsheets with an obvious asymmetric light propagation or one-dimensional (1D) microrods with low propagation loss. The method of tailoring the structures and photonic properties for fabricating different micro-structures would provide enlightenment for the development of tailor-made mini-sized devices for photonic integrated circuits.

Structure of CPV17 polyhedrin determined by the improved analysis of serial femtosecond crystallographic data

DOE PAGES

Ginn, Helen M.; Messerschmidt, Marc; Ji, Xiaoyun; ...

2015-03-09

The X-ray free-electron laser (XFEL) allows the analysis of small weakly diffracting protein crystals, but has required very many crystals to obtain good data. Here we use an XFEL to determine the room temperature atomic structure for the smallest cytoplasmic polyhedrosis virus polyhedra yet characterized, which we failed to solve at a synchrotron. These protein microcrystals, roughly a micron across, accrue within infected cells. We use a new physical model for XFEL diffraction, which better estimates the experimental signal, delivering a high-resolution XFEL structure (1.75 Å), using fewer crystals than previously required for this resolution. The crystal lattice and proteinmore » core are conserved compared with a polyhedrin with less than 10% sequence identity. We explain how the conserved biological phenotype, the crystal lattice, is maintained in the face of extreme environmental challenge and massive evolutionary divergence. Our improved methods should open up more challenging biological samples to XFEL analysis.« less

Cubic-to-tetragonal structural phase transition in Rb1-xCsxCaF3 solid solutions: Thermal expansion and EPR studies

NASA Astrophysics Data System (ADS)

Lahoz, F.; Villacampa, B.; Alcalá, R.; Marquina, C.; Ibarra, M. R.

1997-04-01

The influence of crystal mixing on the structural phase transitions in Rb1-xCsxCaF3 (0=0.44. This transition shows a weak first-order component in the x=0 and 0.1 samples, which is progressively smeared out for x>0.1, indicating a spatial distribution of the critical temperature in those crystals with high ionic substitution rate. In RbCaF3 , another structural phase transition was observed at 20 K with a thermal hysteresis between 20 and 40 K. This transition has not been found in any of the mixed crystals.

Structural characterization of framework-gas interactions in the metal-organic framework Co2(dobdc) by in situ single-crystal X-ray diffraction.

PubMed

Gonzalez, Miguel I; Mason, Jarad A; Bloch, Eric D; Teat, Simon J; Gagnon, Kevin J; Morrison, Gregory Y; Queen, Wendy L; Long, Jeffrey R

2017-06-01

The crystallographic characterization of framework-guest interactions in metal-organic frameworks allows the location of guest binding sites and provides meaningful information on the nature of these interactions, enabling the correlation of structure with adsorption behavior. Here, techniques developed for in situ single-crystal X-ray diffraction experiments on porous crystals have enabled the direct observation of CO, CH 4 , N 2 , O 2 , Ar, and P 4 adsorption in Co 2 (dobdc) (dobdc 4- = 2,5-dioxido-1,4-benzenedicarboxylate), a metal-organic framework bearing coordinatively unsaturated cobalt(ii) sites. All these molecules exhibit such weak interactions with the high-spin cobalt(ii) sites in the framework that no analogous molecular structures exist, demonstrating the utility of metal-organic frameworks as crystalline matrices for the isolation and structural determination of unstable species. Notably, the Co-CH 4 and Co-Ar interactions observed in Co 2 (dobdc) represent, to the best of our knowledge, the first single-crystal structure determination of a metal-CH 4 interaction and the first crystallographically characterized metal-Ar interaction. Analysis of low-pressure gas adsorption isotherms confirms that these gases exhibit mainly physisorptive interactions with the cobalt(ii) sites in Co 2 (dobdc), with differential enthalpies of adsorption as weak as -17(1) kJ mol -1 (for Ar). Moreover, the structures of Co 2 (dobdc)·3.8N 2 , Co 2 (dobdc)·5.9O 2 , and Co 2 (dobdc)·2.0Ar reveal the location of secondary (N 2 , O 2 , and Ar) and tertiary (O 2 ) binding sites in Co 2 (dobdc), while high-pressure CO 2 , CO, CH 4 , N 2 , and Ar adsorption isotherms show that these binding sites become more relevant at elevated pressures.

Probing the crystal structure landscape by doping: 4-bromo, 4-chloro and 4-methylcinnamic acids.

PubMed

Desiraju, Gautam R; Chakraborty, Shaunak; Joseph, Sumy

2018-06-11

Accessing the data points in the crystal structure landscape of a molecule is a challenging task, either experimentally or computationally. We have charted the crystal structure landscape of 4-bromocinnamic acid (4BCA) experimentally and computationally: experimental doping is achieved with 4-methylcinnamic acid (4MCA) to obtain new crystal structures; computational doping is performed with 4-chlorocinnamic acid (4CCA) as a model system, because of the difficulties associated in parameterizing the Br-atom. The landscape of 4CCA is explored experimentally in turn, also by doping it with 4MCA, and is found to bear a close resemblance to the landscape of 4BCA, justifying the ready miscibility of these two halogenated cinnamic acids to form solid solutions without any change in crystal structure. In effect, 4MCA, 4CCA and 4BCA form a commutable group of crystal structures, which may be realized experimentally or computationally, and constitute the landscape. Unlike the results obtained by Kitaigorodskii and others, all but two of the multiple solid solutions obtained in the methyl-doping experiments take structures that are different from the hitherto observed crystal forms of the parent compounds. Even granted that the latter might be inherently polymorphic, this unusual observation provokes the suggestion that solid solution formation may be used to probe the crystal structure landscape. The influence of pi...pi interactions, weak hydrogen bonds and halogen bonds in directing the formation of these new structures is also seen. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Pushing the limits of sulfur SAD phasing: de novo structure solution of the N-terminal domain of the ectodomain of HCV E1

DOE Office of Scientific and Technical Information (OSTI.GOV)

El Omari, Kamel; Iourin, Oleg; Kadlec, Jan

2014-08-01

The sulfur SAD phasing method was successfully used to determine the structure of the N-terminal domain of HCV E1 from low-resolution diffracting crystals by combining data from 32 crystals. Single-wavelength anomalous dispersion of S atoms (S-SAD) is an elegant phasing method to determine crystal structures that does not require heavy-atom incorporation or selenomethionine derivatization. Nevertheless, this technique has been limited by the paucity of the signal at the usual X-ray wavelengths, requiring very accurate measurement of the anomalous differences. Here, the data collection and structure solution of the N-terminal domain of the ectodomain of HCV E1 from crystals that diffractedmore » very weakly is reported. By combining the data from 32 crystals, it was possible to solve the sulfur substructure and calculate initial maps at 7 Å resolution, and after density modication and phase extension using a higher resolution native data set to 3.5 Å resolution model building was achievable.« less

Crystal structure, vibrational and DFT simulation studies of melaminium dihydrogen phosphite monohydrate

NASA Astrophysics Data System (ADS)

Arjunan, V.; Kalaivani, M.; Marchewka, M. K.; Mohan, S.

2013-08-01

The crystal structure investigations of melamine with phosphorous acid, namely melaminium dihydrogenphosphite monohydrate (C3N6H7·H2PO3·H2O) have been investigated by means of single crystal X-ray diffraction method. The title compound crystallizes in monoclinic crystal system, and the space group is P21/c with a = 10.069 Å, b = 21.592 Å, c = 12.409 Å and Z = 12. The vibrational assignments and analysis of melaminium dihydrogen phosphite monohydrate have also been performed by FTIR, FT-Raman and far-infrared spectral studies. The quantum chemical simulations were performed with DFT (B3LYP) method using 6-31G**, cc-pVTZ, and 6-311++G** basis sets to determine the energy, structural, thermodynamic parameters and vibrational frequencies of melaminium dihydrogen phosphite monohydrate. The hydrogen atom from phosphorous acid was transferred to the melamine molecule giving the singly protonated melaminium cation. The ability of ions to form spontaneous three-dimensional structure through weak Osbnd H···O and Nsbnd H···O hydrogen bonds shows notable vibrational effects.

Crystal and molecular structure of eight organic acid-base adducts from 2-methylquinoline and different acids

NASA Astrophysics Data System (ADS)

Zhang, Jing; Jin, Shouwen; Tao, Lin; Liu, Bin; Wang, Daqi

2014-08-01

Eight supramolecular complexes with 2-methylquinoline and acidic components as 4-aminobenzoic acid, 2-aminobenzoic acid, salicylic acid, 5-chlorosalicylic acid, 3,5-dinitrosalicylic acid, malic acid, sebacic acid, and 1,5-naphthalenedisulfonic acid were synthesized and characterized by X-ray crystallography, IR, mp, and elemental analysis. All of the complexes are organic salts except compound 2. All supramolecular architectures of 1-8 involve extensive classical hydrogen bonds as well as other noncovalent interactions. The results presented herein indicate that the strength and directionality of the classical hydrogen bonds (ionic or neutral) between acidic components and 2-methylquinoline are sufficient to bring about the formation of binary organic acid-base adducts. The role of weak and strong noncovalent interactions in the crystal packing is ascertained. These weak interactions combined, the complexes 1-8 displayed 2D-3D framework structure.

Structural study of quasi-one-dimensional vanadium pyroxene LiVSi{sub 2}O{sub 6} single crystals

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ishii, Yuto; Matsushita, Yoshitaka; Oda, Migaku

Single crystals of quasi-one-dimensional vanadium pyroxene LiVSi{sub 2}O{sub 6} were synthesized and the crystal structures at 293 K and 113 K were studied using X-ray diffraction experiments. We found a structural phase transition from the room-temperature crystal structure with space group C2/c to a low-temperature structure with space group P2{sub 1}/c, resulting from a rotational displacement of SiO{sub 4} tetrahedra. The temperature dependence of magnetic susceptibility shows a broad maximum around 116 K, suggesting an opening of the Haldane gap expected for one-dimensional antiferromagnets with S=1. However, an antiferromagnetic long-range order was developed below 24 K, probably caused by amore » weak inter-chain magnetic coupling in the compound. - Graphical abstract: Low temperature crystal structure of LiVSi{sub 2}O{sub 6} and an orbital arrangement within the V-O zig-zag chain along the c-axis. - Highlights: • A low temperature structure of LiVSi{sub 2}O{sub 6} was determined by single crystal X-ray diffraction measurements. • The origin of the structural transition is a rotational displacement of SiO{sub 4} tetrahedra. • The uniform orbital overlap in the V-O zigzag chain makes the system a quasi one-dimensional antiferromagnet.« less

Magnetic assembly of nonmagnetic particles into photonic crystal structures.

PubMed

He, Le; Hu, Yongxing; Kim, Hyoki; Ge, Jianping; Kwon, Sunghoon; Yin, Yadong

2010-11-10

We report the rapid formation of photonic crystal structures by assembly of uniform nonmagnetic colloidal particles in ferrofluids using external magnetic fields. Magnetic manipulation of nonmagnetic particles with size down to a few hundred nanometers, suitable building blocks for producing photonic crystals with band gaps located in the visible regime, has been difficult due to their weak magnetic dipole moment. Increasing the dipole moment of magnetic holes has been limited by the instability of ferrofluids toward aggregation at high concentration or under strong magnetic field. By taking advantage of the superior stability of highly surface-charged magnetite nanocrystal-based ferrofluids, in this paper we have been able to successfully assemble 185 nm nonmagnetic polymer beads into photonic crystal structures, from 1D chains to 3D assemblies as determined by the interplay of magnetic dipole force and packing force. In a strong magnetic field with large field gradient, 3D photonic crystals with high reflectance (83%) in the visible range can be rapidly produced within several minutes, making this general strategy promising for fast creation of large-area photonic crystals using nonmagnetic particles as building blocks.

A new crystal form of a hyperthermophilic endocellulase

PubMed Central

Kataoka, Misumi; Ishikawa, Kazuhiko

2014-01-01

The hyperthermophilic glycoside hydrolase family endocellulase 12 from the archaeon Pyrococcus furiosus (EGPf; Gene ID PF0854; EC 3.2.1.4) catalyzes the hydrolytic cleavage of the β-1,4-glucosidic linkage in β-glucan in lignocellulose biomass. A crystal of EGPf was previously prepared at pH 9.0 and its structure was determined at an atomic resolution of 1.07 Å. This article reports the crystallization of EGPf at the more physiologically relevant pH of 5.5. Structure determination showed that this new crystal form has the symmetry of space group C2. Two molecules of the enzyme are observed in the asymmetric unit. Crystal packing is weak at pH 5.5 owing to two flexible interfaces between symmetry-related molecules. Comparison of the EGPf structures obtained at pH 9.0 and pH 5.5 reveals a significant conformational difference at the active centre and in the surface loops. The interfaces in the vicinity of the flexible surface loops impact the quality of the EGPf crystal. PMID:25005081

1-[6-(1H-Indol-1-yl)pyridin-2-yl]-1H-indole-3-carbaldehyde.

PubMed

Ramathilagam, C; Umarani, P R; Venkatesan, N; Rajakumar, P; Gunasekaran, B; Manivannan, V

2014-02-01

In the title compound, C22H15N3O, the dihedral angle between the two indole units is 33.72 (3)°. The mol-ecular structure features a weak intra-molecular C-H⋯N inter-action. In the crystal, weak C-H⋯O and C-H⋯π inter-actions, forming a two-dimensional network parallel to the bc plane.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kuz'mina, L. G., E-mail: kuzmina@igic.ras.ru; Kucherepa, N. S.; Syrbu, S. A.

The crystal and molecular structure of p-(decaoxybenzylidene)-p'-toluidine C{sub 10}H{sub 21}O-C{sub 6}H{sub 4}-CH=N-C{sub 6}H{sub 4}-CH{sub 3} is studied. The molecule is nearly planar. In the crystal packing, loose regions formed by aliphatic fragments of molecules alternate with pseudostacks of aromatic fragments of molecules that are related by the centers of symmetry. The stacks are built of dimers, in which molecules are linked by {pi}-stacking interactions between benzene rings. There are no weak directional interactions between dimers in a stack. The presence of a single structure-forming element in the crystal, namely, the {pi}-stacking interactions in the dimers, along with the similarity ofmore » the crystal packing to that of the C{sub 8}H{sub 17}O-homologue, which forms a nematic mesophase on melting, indicate that the crystals under study should exhibit nematic properties.« less

Coexistence of Weak Ferromagnetism and Ferroelectricity in the High Pressure LiNbO3-Type Phase of FeTiO3

NASA Astrophysics Data System (ADS)

Varga, T.; Kumar, A.; Vlahos, E.; Denev, S.; Park, M.; Hong, S.; Sanehira, T.; Wang, Y.; Fennie, C. J.; Streiffer, S. K.; Ke, X.; Schiffer, P.; Gopalan, V.; Mitchell, J. F.

2009-07-01

We report the magnetic and electrical characteristics of polycrystalline FeTiO3 synthesized at high pressure that is isostructural with acentric LiNbO3 (LBO). Piezoresponse force microscopy, optical second harmonic generation, and magnetometry demonstrate ferroelectricity at and below room temperature and weak ferromagnetism below ˜120K. These results validate symmetry-based criteria and first-principles calculations of the coexistence of ferroelectricity and weak ferromagnetism in a series of transition metal titanates crystallizing in the LBO structure.

Coexistence of weak ferromagnetism and ferroelectricity in the high pressure LiNbO3-type phase of FeTiO3.

PubMed

Varga, T; Kumar, A; Vlahos, E; Denev, S; Park, M; Hong, S; Sanehira, T; Wang, Y; Fennie, C J; Streiffer, S K; Ke, X; Schiffer, P; Gopalan, V; Mitchell, J F

2009-07-24

We report the magnetic and electrical characteristics of polycrystalline FeTiO_{3} synthesized at high pressure that is isostructural with acentric LiNbO_{3} (LBO). Piezoresponse force microscopy, optical second harmonic generation, and magnetometry demonstrate ferroelectricity at and below room temperature and weak ferromagnetism below approximately 120 K. These results validate symmetry-based criteria and first-principles calculations of the coexistence of ferroelectricity and weak ferromagnetism in a series of transition metal titanates crystallizing in the LBO structure.

Structure, optical and phonon properties of bulk and nanocrystalline Al2-xScx(WO4)3 solid solutions doped with Cr3+

NASA Astrophysics Data System (ADS)

Mączka, M.; Hermanowicz, K.; Pietraszko, A.; Yordanova, A.; Koseva, I.

2014-01-01

Pure and Cr3+ doped nanosized Al2-xScx(WO4)3 solid solutions were prepared by co-precipitation method as well as Al2-xScx(WO4)3 single crystals were grown by high-temperature flux method. The obtained samples were characterized by X-ray, Raman, IR, absorption and luminescence methods. Single crystal X-ray diffraction showed that AlSc(WO4)3 is orthorhombic at room temperature with space group Pnca and trivalent cations are statistically distributed. Raman and IR studies showed that Al2-xScx(WO4)3 solid solutions show "two mode" behavior. They also showed that vibrational properties of nanosized samples have been weakly modified in comparison with the bulk materials. The luminescence and absorption spectra revealed that chromium ions occupy two sites of weak and strong crystal field strength.

Controlling Chirality of Entropic Crystals.

PubMed

Damasceno, Pablo F; Karas, Andrew S; Schultz, Benjamin A; Engel, Michael; Glotzer, Sharon C

2015-10-09

Colloidal crystal structures with complexity and diversity rivaling atomic and molecular crystals have been predicted and obtained for hard particles by entropy maximization. However, thus far homochiral colloidal crystals, which are candidates for photonic metamaterials, are absent. Using Monte Carlo simulations we show that chiral polyhedra exhibiting weak directional entropic forces self-assemble either an achiral crystal or a chiral crystal with limited control over the crystal handedness. Building blocks with stronger faceting exhibit higher selectivity and assemble a chiral crystal with handedness uniquely determined by the particle chirality. Tuning the strength of directional entropic forces by means of particle rounding or the use of depletants allows for reconfiguration between achiral and homochiral crystals. We rationalize our findings by quantifying the chirality strength of each particle, both from particle geometry and potential of mean force and torque diagrams.

Mutation of Surface Residues to Promote Crystallization of Activated Factor XI as a Complex with Benzamidine: an Essential Step for the Iterative Structure-Based Design of Factor XI Inhibitors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jin,L.; Pandey, P.; Babine, R.

Activated factor XI (FXIa) is a key enzyme in the amplification phase of the blood-coagulation cascade. Thus, a selective FXIa inhibitor may have lesser bleeding liabilities and provide a safe alternative for antithrombosis therapy to available drugs on the market. In a previous report, the crystal structures of the catalytic domain of FXIa (rhFXI370-607) in complex with various ecotin mutants have been described [Jin et al. (2005), Journal of Biological Chemistry 280, 4704-4712]. However, ecotin forms a matrix-like interaction with rhFXI370-607 and is impossible to displace with small-molecule inhibitors; ecotin crystals are therefore not suitable for iterative structure-based ligand design.more » In addition, rhFXI370-607 did not crystallize in the presence of small-molecule ligands. In order to obtain the crystal structure of rhFXI370-607 with a weak small-molecule ligand, namely benzamidine, several rounds of surface-residue mutation were implemented to promote crystal formation of rhFXI370-607. A quadruple mutant of rhFXI370-607 (rhFXI370-607-S434A, T475A, C482S, K437A) readily crystallized in the presence of benzamidine. The benzamidine in the preformed crystals was easily exchanged with other FXIa small-molecule inhibitors. These crystals have facilitated the structure-based design of small-molecule FXIa inhibitors.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chao, Tzu-Ling; Yang, Chen-I., E-mail: ciyang@thu.edu.tw

The preparations and properties of three new homochiral three-dimensional (3D) coordination polymers, [M(D-cam)(pyz)(H{sub 2}O){sub 2}]{sub n} (M=Co (1) and Ni (2); D-H{sub 2}cam=(+) D-camphoric acid; pyz=pyrazine) and [Mn{sub 2}(D-cam){sub 2}(H{sub 2}O){sub 2}] (3), under solvothermal conditions is described. Single-crystal X-ray diffraction analyses revealed that all of compounds are homochiral 3D structure. 1 and 2 are isostructural and crystallize in the trigonal space group P3{sub 2}21, while 3 crystallizes in monoclinic space group P2{sub 1}. The structure of 1 and 2 consists of metal-D-cam helical chains which are pillared with pyrazine ligands into a 3D framework structure and 3 features amore » 3D homochiral framework involving one-dimensional manganese-carboxylate chains that are aligned parallel to the b axis. Magnetic susceptibility data of all compounds were collected. The findings indicate that μ{sub 2}-pyrazine dominate weak antiferromagnetic coupling within 1 and 2, while 3 exhibits antiferromagnetic behavior through the carboxylate groups of D-cam ligand. -- Graphical abstract: The preparations and properties of three new homochiral three-dimensional (3D) coordination polymers, [M(D-cam)(pyz)(H{sub 2}O){sub 2}]{sub n} (M=Co (1) and Ni (2); D-H{sub 2}cam=(+) D-camphoric acid; pyz=pyrazine) and [Mn{sub 2}(D-cam){sub 2}(H{sub 2}O){sub 2}] (3), under solvothermal conditions is described. Single-crystal X-ray diffraction analyses revealed that all of compounds are homochiral 3D structure. 1 and 2 are isostructural and crystallize in the trigonal space group P3{sub 2}21, while 3 crystallizes in monoclinic space group P2{sub 1}. The structure of 1 and 2 consists of metal-D-cam helical chains which are pillared with pyrazine ligands into a 3D framework structure and 3 features a 3D homochiral framework involving one-dimensional manganese-carboxylate chains that are aligned parallel to the b axis. Magnetic susceptibility data of all compounds were collected. The findings indicate that μ{sub 2}-pyrazine dominate weak antiferromagnetic coupling within 1 and 2, while 3 exhibits antiferromagnetic behavior through the carboxylate groups of D-cam ligand. Highlights: • Three homochiral 3D coordination polymers were synthesized. • 1 and 2 are 3D structure with metal-D-cam helical chains pillared by pyrazine. • 3 shows a 3D homochiral framework involving 1D manganese-carboxylate chains. • Magnetic data analysis indicates that 1–3 exhibit weak antiferromagnetic coupling.« less

Highly robust crystalsome via directed polymer crystallization at curved liquid/liquid interface

PubMed Central

Wang, Wenda; Qi, Hao; Zhou, Tian; Mei, Shan; Han, Lin; Higuchi, Takeshi; Jinnai, Hiroshi; Li, Christopher Y.

2016-01-01

Lipids and amphiphilic block copolymers spontaneously self-assemble in water to form a plethora of micelles and vesicles. They are typically fluidic in nature and often mechanically weak for applications such as drug delivery and gene therapeutics. Mechanical properties of polymeric materials could be improved by forming crystalline structures. However, most of the self-assembled micelles and vesicles have curved surfaces and precisely tuning crystallization within a nanoscale curved space is challenging, as the curved geometry is incommensurate with crystals having three-dimensional translational symmetry. Herein, we report using a miniemulsion crystallization method to grow nanosized, polymer single-crystal-like capsules. We coin the name crystalsome to describe this unique structure, because they are formed by polymer lamellar crystals and their structure mimics liposomes and polymersomes. Using poly(L-lactic acid) (PLLA) as the model polymer, we show that curved water/p-xylene interface formed by the miniemulsion process can guide the growth of PLLA single crystals. Crystalsomes with the size ranging from ∼148 nm to over 1 μm have been formed. Atomic force microscopy measurement demonstrate a two to three orders of magnitude increase in bending modulus compared with conventional polymersomes. We envisage that this novel structure could shed light on investigating spherical crystallography and drug delivery. PMID:26837260

The application of crystal soaking technique to study the effect of zinc and cresol on insulinotropin crystals grown from a saline solution.

PubMed

Kim, Y; Haren, A M

1995-11-01

The purpose of this study is to investigate the effect of zinc and cresol on the structure of insulinotropin crystals. Insulinotropin crystals grown from a saline solution were treated with zinc and/or m-cresol using a crystal soaking technique. The effects of these additives on the crystal structure were investigated with powder X-ray diffraction, photomicrography, and differential scanning calorimetry. The molecular interaction between insulinotropin and m-trifluorocresol in solution was also studied by 19F NMR: The data suggest that the original crystals grown from a saline solution have relatively weak lattice forces. After the addition of m-cresol to the suspension of the insulinotropin crystals, the crystals were immediately rendered amorphous. The m-cresol molecules which diffused into the crystals through solvent channels may have disturbed the lattice interactions that maintain the integrity of the crystal. In contrast, the zinc added to the suspension stabilized the crystal lattice so that the subsequent addition of m-cresol did not alter the integrity of the crystals. A marked increase in melting point (206 degrees versus 184 degrees) and heat of fusion (24.6 J/g versus 1.4 J/g) of the crystals was observed after the treatment with zinc. The solubility of the zinc treated crystals in a pH 7.1 phosphate buffered saline was 1/20 of that of the original crystals. When the insulinotropin crystals were treated with the additives using a crystal soaking method, the crystals underwent structural changes. Zinc stabilized the crystal lattice, and reduced the solubility of the peptide.

Weak crystallization theory of metallic alloys

DOE PAGES

Martin, Ivar; Gopalakrishnan, Sarang; Demler, Eugene A.

2016-06-20

Crystallization is one of the most familiar, but hardest to analyze, phase transitions. The principal reason is that crystallization typically occurs via a strongly first-order phase transition, and thus rigorous treatment would require comparing energies of an infinite number of possible crystalline states with the energy of liquid. A great simplification occurs when crystallization transition happens to be weakly first order. In this case, weak crystallization theory, based on unbiased Ginzburg-Landau expansion, can be applied. Even beyond its strict range of validity, it has been a useful qualitative tool for understanding crystallization. In its standard form, however, weak crystallization theorymore » cannot explain the existence of a majority of observed crystalline and quasicrystalline states. Here we extend the weak crystallization theory to the case of metallic alloys. In this paper, we identify a singular effect of itinerant electrons on the form of weak crystallization free energy. It is geometric in nature, generating strong dependence of free energy on the angles between ordering wave vectors of ionic density. That leads to stabilization of fcc, rhombohedral, and icosahedral quasicrystalline (iQC) phases, which are absent in the generic theory with only local interactions. Finally, as an application, we find the condition for stability of iQC that is consistent with the Hume-Rothery rules known empirically for the majority of stable iQC; namely, the length of the primary Bragg-peak wave vector is approximately equal to the diameter of the Fermi sphere.« less

Crystal and Magnetic Structures in Layered, Transition Metal Dihalides and Trihalides

DOE PAGES

McGuire, Michael A.

2017-04-27

Materials composed of two dimensional layers bonded to one another through weak van der Waals interactions often exhibit strongly anisotropic behaviors and can be cleaved into very thin specimens and sometimes into monolayer crystals. Interest in such materials is driven by the study of low dimensional physics and the design of functional heterostructures. Binary compounds with the compositions MX 2 and MX 3 where M is a metal cation and X is a halogen anion often form such structures. Magnetism can be incorporated by choosing a transition metal with a partially filled d-shell for M, enabling ferroic responses for enhancedmore » functionality. Here we give a brief overview of binary transition metal dihalides and trihalides, summarizing their crystallographic properties and long-range-ordered magnetic structures, focusing on those materials with layered crystal structures and partially filled d-shells required for combining low dimensionality and cleavability with magnetism.« less

The structure of small, vapor-deposited particles. II - Experimental study of particles with hexagonal profile

NASA Technical Reports Server (NTRS)

Yacaman, M. J.; Heinemann, K.; Yang, C. Y.; Poppa, H.

1979-01-01

'Multiply-twinned' gold particles with hexagonal bright field TEM profile were determined to be icosahedra composed of 20 identical and twin-related tetrahedral building units that do not have an fcc structure. The crystal structure of these slightly deformed tetrahedra is rhombohedral. Experimental evidence supporting this particle model was obtained by selected-zone dark field and weak beam dark field electron microscopy. In conjunction with the results of part I, it has been concluded that multiply-twinned gold particles of pentagonal or hexagonal profile that are found during the early stages of the vapor deposition growth process on alkali halide surfaces do not have an fcc crystal structure, which is in obvious contrast to the structure of bulk gold.

Efficiency of surface plasmon excitation at the photonic crystal – metal interface

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kuznetsova, T I; Raspopov, N A

2015-11-30

We report the results of a theoretical investigation of light wave transformation in a one-dimensional photonic crystal. The scheme considered comprises an incident wave directed in parallel with layers of the photonic crystal under an assumption that the wave vector is far from a forbidden zone. Expressions for propagating and evanescent electromagnetic waves in a periodic medium of the photonic crystal are obtained. It is found that the transverse structure of the propagating wave comprises a strong constant component and a weak oscillating component with a period determined by that of the photonic crystal. On the contrary, the dependence ofmore » evanescent waves on transverse coordinates is presented by a strong oscillating component and a weak constant component. The process of transformation of propagating waves to evanescent waves at a crystal – metal interface is investigated. Parameters of the photonic crystal typical for synthetic opals are used in all numerical simulations. The theoretical approach elaborated yields in an explicit form the dependence of the amplitude of a generated surface wave on the period of the dielectric function modulation in the photonic crystal. The results obtained show that in the conditions close to plasmon resonance the amplitude of the surface wave may be on the order of or even exceed that of the initial incident wave. (light wave transformation)« less

Structural investigation of cooperite (PtS) crystals

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rozhdestvina, V. I., E-mail: veronika@ascnet.ru; Udovenko, A. A.; Rubanov, S. V.

2016-03-15

The single-crystal structure of cooperite, a natural platinum sulfide PtS, is studied by X-ray diffraction supported by high-resolution scanning transmission electron microscopy and X-ray spectrum microanalysis. It is found that, in addition to the main reflections corresponding to the known tetragonal cell (a = 3.47 and c = 6.11 Å; space group P4{sub 2}/mmc), many weak reflections with intensities I ≤ 60σ(I) are clearly observed. These reflections fit the tetragonal cell (space group I4/mmm) with doubled parameters. In structures with small (P4{sub 2}/mmc) and large (I4/mmm) cells, the S atoms occupy statistically two special positions. It is shown that themore » chemical composition of the cooperite crystals deviates from the stoichiometric composition: sulfur-deficient specimens predominate.« less

Crystal structure of 2-amino-pyridinium 6-chloro-nicotinate.

PubMed

Jasmine, N Jeeva; Rajam, A; Muthiah, P Thomas; Stanley, N; Razak, I Abdul; Rosli, M Mustaqim

2015-09-01

In the title salt, C5H7N(+)·C6H3ClNO(-), the 2-amino-pyri-din-ium cation inter-acts with the carboxyl-ate group of the 6-chloro-nicotinate anion through a pair of independent N-H⋯O hydrogen bonds, forming an R 2 (2)(8) ring motif. In the crystal, these dimeric units are connected further via N-H⋯O hydrogen bonds, forming chains along [001]. In addition, weak C-H⋯N and C-H⋯O hydrogen bonds, together with weak π-π inter-actions, with centroid-centroid distances of 3.6560 (5) and 3.6295 (5) Å, connect the chains, forming a two-dimensional network parallel to (100).

New investigations of the guanine trichloro cuprate(II) complex crystal

NASA Astrophysics Data System (ADS)

Fabijanić, Ivana; Matković-Čalogović, Dubravka; Pilepić, Viktor; Ivanišević, Irena; Mohaček-Grošev, Vlasta; Sanković, Krešimir

2017-01-01

Crystals of the guanine trichloro cuprate(II) complex, (HGua)2[Cu2Cl6]·2H2O (HGua = protonated guanine), were prepared and analysed by spectroscopic (IR, Raman) and computational methods. A new single-crystal X-ray diffraction analysis was conducted to obtain data with lower standard uncertainties than those in the previously published structure. Raman and IR spectroscopy and quantum-mechanical analysis gave us new insight into the vibrational states of the (HGua)2[Cu2Cl6]·2H2O crystal. The vibrational spectra of the crystal were assigned by performing a normal coordinate analysis for a free dimer with a centre of inversion as the only symmetry element. The stretching vibration observed at 279 cm-1 in the infrared spectrum corresponds to the N-Cu bond. The noncovalent interaction (NCI) plots and quantum theory of atoms in molecules (QTAIM) analysis of the electron density obtained from periodic DFT calculations elucidated the interactions that exist within the crystal structure. Closed-shell ionic attractions, as well as weak and medium strength hydrogen bonds, prevailed in the crystal packing.

Phase behavior and crystal structure of 3-(1-naphthyloxy)- and 3-(4-indolyloxy)-propane-1,2-diol, synthetic precursors of chiral drugs propranolol and pindolol

NASA Astrophysics Data System (ADS)

Bredikhin, Alexander A.; Gubaidullin, Aidar T.; Bredikhina, Zemfira A.; Fayzullin, Robert R.; Samigullina, Aida I.; Zakharychev, Dmitry V.

2013-08-01

Valuable precursors of popular chiral drugs propranolol and pindolol, 3-(1-naphthyloxy)-propane-1,2-diol 3 and 3-(4-indolyloxy)-propane-1,2-diol 4 were investigated by IR spectroscopy, DSC, and X-ray diffraction methods. Both compounds, crystallizing from enantiopure feed material, form "guaifenesin-like" crystal packing in which the classic H-bonded bilayers, framed in both sides by hydrophobic fragments of the molecules, acts as the basic crystal-forming motif. Diol 4 prone to spontaneous resolution and conserves its packing pattern crystallizing from racemate. Under the same conditions, diol 3 forms weakly stable solid racemic compound. Some reasons for such a behavior are identified and discussed.

2-Ferrocenyl-3-meth­oxy-6-methyl­pyridine

PubMed Central

Xu, Chen; Hao, Xin-Qi; Liu, Fang; Wu, Xiu-Juan; Song, Mao-Ping

2009-01-01

In the title compound, [Fe(C5H5)(C12H12NO)], the dihedral angle between the pyridyl and substituted cyclo­penta­dienyl rings is 23.58 (3)°. The crystal structure is characterized by weak inter­molecular C—H⋯N hydrogen-bonding contacts, leading to the formation of chains running parallel to the n-glide planes. A weak inter­molecular C—H⋯π contact is also present. PMID:21583761

Crystal structure of 3-(adamantan-1-yl)-4-(4-chloro-phen-yl)-1H-1,2,4-triazole-5(4H)-thione.

PubMed

Al-Wabli, Reem I; El-Emam, Ali A; Alroqi, Obaid S; Chidan Kumar, C S; Fun, Hoong-Kun

2015-02-01

The title compound, C18H20ClN3S, is a functionalized triazoline-3-thione derivative. The benzene ring is almost perpendic-ular to the planar 1,2,4-triazole ring [maximum deviation = 0.007 (1) Å] with a dihedral angle of 89.61 (5)° between them and there is an adamantane substituent at the 3-position of the triazole-thione ring. In the crystal, N-H⋯S hydrogen-bonding inter-actions link the mol-ecules into chains extending along the c-axis direction. The crystal packing is further stabilized by weak C-H⋯π inter-actions that link adjacent chains into a two-dimensional structure in the bc plane. The crystal studied was an inversion twin with a 0.50 (3):0.50 (3) domain ratio.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kuz'mina, L. G., E-mail: kuzmina@igic.ras.ru; Kucherepa, N. S.; Rodnikova, M. N.

The molecular and crystal structures of two p-(alkoxybenzylidene)-p'-toluidines C{sub 5}H{sub 11}O-C{sub 6}H{sub 4}-CH=N-C{sub 6}H{sub 4}-CH{sub 3} (1) and C{sub 8}H{sub 17}O-C{sub 6}H{sub 4}-CH=N-C{sub 6}H{sub 4}-CH{sub 3} (2), which form the nematic phase upon melting, is determined by X-ray diffraction. The geometry of the benzylideneaniline fragments in molecules 1 and 2 is actually identical. The crystal packings of 1 and 2 are characterized by the alternation of layers formed by loosely packed aliphatic fragments of molecules and layers of closely packed aromatic fragments. The packing in the aromatic regions of 1 follows the parquet pattern. The crystal packing of 2 hasmore » a stacking structure, which is formed by {pi}-stacking dimers superimposed on one another. The formation of the mesogenic phase upon melting of crystals 1 is due to the disturbance of the structurality of loose aliphatic layers with retention of the structure of the aromatic regions, which are stabilized by the cooperative effect of weak directed C-H ... {pi}-system interactions. The mesogenic phase of crystals 2 is formed upon melting as a consequence of the retention of the structure of {pi}-stacking dimers.« less

Synthesis, characterization, and application of two Al(OR(F))3 Lewis superacids.

PubMed

Kraft, Anne; Trapp, Nils; Himmel, Daniel; Böhrer, Hannes; Schlüter, Peter; Scherer, Harald; Krossing, Ingo

2012-07-23

We report herein the synthesis and full characterization of the donor-free Lewis superacids Al(OR(F))(3) with OR(F) = OC(CF(3))(3) (1) and OC(C(5)F(10))C(6)F(5) (2), the stabilization of 1 as adducts with the very weak Lewis bases PhF, 1,2-F(2)C(6)H(4), and SO(2), as well as the internal C-F activation pathway of 1 leading to Al(2)(F)(OR(F))(5) (4) and trimeric [FAl(OR(F))(2)](3) (5, OR(F) = OC(CF(3))(3)). Insights have been gained from NMR studies, single-crystal structure determinations, and DFT calculations. The usefulness of these Lewis acids for halide abstractions has been demonstrated by reactions with trityl chloride (NMR; crystal structures). The trityl salts allow the introduction of new, heteroleptic weakly coordinating [Cl-Al(OR(F))(3)](-) anions, for example, by hydride or alkyl abstraction reactions. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Broadband and broadangle SPP antennas based on plasmonic crystals with linear chirp.

PubMed

Bouillard, J-S; Vilain, S; Dickson, W; Wurtz, G A; Zayats, A V

2012-01-01

Plasmonic technology relies on the coupling of light to surface electromagnetic modes on smooth or structured metal surfaces. While some applications utilise the resonant nature of surface polaritons, others require broadband characteristics. We demonstrate unidirectional and broadband plasmonic antennas with large acceptance angles based on chirped plasmonic gratings. Near-field optical measurements have been used to visualise the excitation of surface plasmon polaritons by such aperiodic structures. These weakly aperiodic plasmonic crystals allow the formation of a trapped rainbow-type effect in a two-dimensional geometry as surface polaritons of different frequencies are coherently excited in different locations over the plasmonic structure. Both the crystal's finite size and the finite lifetime of plasmonic states are crucial for the generation of broadband surface plasmon polaritons. This approach presents new opportunities for building unidirectional, broadband and broad-angle plasmonic couplers for sensing purposes, information processing, photovoltaic applications and shaping and manipulating ultrashort optical pulses.

Broadband and broadangle SPP antennas based on plasmonic crystals with linear chirp

PubMed Central

Bouillard, J.-S; Vilain, S.; Dickson, W.; Wurtz, G. A.; Zayats, A. V.

2012-01-01

Plasmonic technology relies on the coupling of light to surface electromagnetic modes on smooth or structured metal surfaces. While some applications utilise the resonant nature of surface polaritons, others require broadband characteristics. We demonstrate unidirectional and broadband plasmonic antennas with large acceptance angles based on chirped plasmonic gratings. Near-field optical measurements have been used to visualise the excitation of surface plasmon polaritons by such aperiodic structures. These weakly aperiodic plasmonic crystals allow the formation of a trapped rainbow-type effect in a two-dimensional geometry as surface polaritons of different frequencies are coherently excited in different locations over the plasmonic structure. Both the crystal's finite size and the finite lifetime of plasmonic states are crucial for the generation of broadband surface plasmon polaritons. This approach presents new opportunities for building unidirectional, broadband and broad-angle plasmonic couplers for sensing purposes, information processing, photovoltaic applications and shaping and manipulating ultrashort optical pulses. PMID:23170197

Structural characterization of framework–gas interactions in the metal–organic framework Co 2 (dobdc) by in situ single-crystal X-ray diffraction

DOE PAGES

Gonzalez, Miguel I.; Mason, Jarad A.; Bloch, Eric D.; ...

2017-04-19

The crystallographic characterization of framework–guest interactions in metal–organic frameworks allows the location of guest binding sites and provides meaningful information on the nature of these interactions, enabling the correlation of structure with adsorption behavior. Here, techniques developed for in situ single-crystal X-ray diffraction experiments on porous crystals have enabled the direct observation of CO, CH 4, N 2, O 2, Ar, and P 4 adsorption in Co2(dobdc) (dobdc 4– = 2,5-dioxido-1,4-benzenedicarboxylate), a metal–organic framework bearing coordinatively unsaturated cobalt(II) sites. All these molecules exhibit such weak interactions with the high-spin cobalt(II) sites in the framework that no analogous molecular structures exist,more » demonstrating the utility of metal–organic frameworks as crystalline matrices for the isolation and structural determination of unstable species. Notably, the Co–CH 4 and Co–Ar interactions observed in Co 2(dobdc) represent, to the best of our knowledge, the first single-crystal structure determination of a metal–CH 4 interaction and the first crystallographically characterized metal–Ar interaction. Analysis of low-pressure gas adsorption isotherms confirms that these gases exhibit mainly physisorptive interactions with the cobalt(II) sites in Co 2(dobdc), with differential enthalpies of adsorption as weak as –17(1) kJ mol –1 (for Ar). Moreover, the structures of Co 2(dobdc)·3.8N 2, Co 2(dobdc)·5.9O 2, and Co 2(dobdc)·2.0Ar reveal the location of secondary (N 2, O 2, and Ar) and tertiary (O 2) binding sites in Co 2(dobdc), while high-pressure CO 2, CO, CH 4, N 2, and Ar adsorption isotherms show that these binding sites become more relevant at elevated pressures.« less

Optical conductivity of alpha-Mn

NASA Technical Reports Server (NTRS)

Scoles, K. J.; Christy, R. W.

1982-01-01

The optical constants were measured at room temperature in the photon-energy range 0.6 to 6.5 eV on evaporated thin films. Evaporation conditions were chosen that gave the alpha-Mn crystal structure with reasonably large grains. The optical conductivity was separated into intraband and interband contributions by fitting to the Drude formula at low energies. The results are anomalous in comparison to other 3d transition metals. The free-electron lifetime is exceptionally sort (in agreement with the large dc resistivity of Mn), and the interband transitions seem unusually weak at the lower energies. Possible explanations related to the complicated crystal structure of alpha-Mn are discussed.

Acemetacin cocrystal structures by powder X-ray diffraction.

PubMed

Bolla, Geetha; Chernyshev, Vladimir; Nangia, Ashwini

2017-05-01

Cocrystals of acemetacin drug (ACM) with nicotinamide (NAM), p -aminobenzoic acid (PABA), valerolactam (VLM) and 2-pyridone (2HP) were prepared by melt crystallization and their X-ray crystal structures determined by high-resolution powder X-ray diffraction. The powerful technique of structure determination from powder data (SDPD) provided details of molecular packing and hydrogen bonding in pharmaceutical cocrystals of acemetacin. ACM-NAM occurs in anhydrate and hydrate forms, whereas the other structures crystallized in a single crystalline form. The carboxylic acid group of ACM forms theacid-amide dimer three-point synthon R 3 2 (9) R 2 2 (8) R 3 2 (9) with three different syn amides (VLM, 2HP and caprolactam). The conformations of the ACM molecule observed in the crystal structures differ mainly in the mutual orientation of chlorobenzene fragment and the neighboring methyl group, being anti (type I) or syn (type II). ACM hydrate, ACM-NAM, ACM-NAM-hydrate and the piperazine salt of ACM exhibit the type I conformation, whereas ACM polymorphs and other cocrystals adopt the ACM type II conformation. Hydrogen-bond interactions in all the crystal structures were quantified by calculating their molecular electrostatic potential (MEP) surfaces. Hirshfeld surface analysis of the cocrystal surfaces shows that about 50% of the contribution is due to a combination of strong and weak O⋯H, N⋯H, Cl⋯H and C⋯H interactions. The physicochemical properties of these cocrystals are under study.

Acemetacin cocrystal structures by powder X-ray diffraction

PubMed Central

Bolla, Geetha

2017-01-01

Cocrystals of acemetacin drug (ACM) with nicotinamide (NAM), p-aminobenzoic acid (PABA), valerolactam (VLM) and 2-pyridone (2HP) were prepared by melt crystallization and their X-ray crystal structures determined by high-resolution powder X-ray diffraction. The powerful technique of structure determination from powder data (SDPD) provided details of molecular packing and hydrogen bonding in pharmaceutical cocrystals of acemetacin. ACM–NAM occurs in anhydrate and hydrate forms, whereas the other structures crystallized in a single crystalline form. The carboxylic acid group of ACM forms theacid–amide dimer three-point synthon R 3 2(9)R 2 2(8)R 3 2(9) with three different syn amides (VLM, 2HP and caprolactam). The conformations of the ACM molecule observed in the crystal structures differ mainly in the mutual orientation of chlorobenzene fragment and the neighboring methyl group, being anti (type I) or syn (type II). ACM hydrate, ACM—NAM, ACM–NAM-hydrate and the piperazine salt of ACM exhibit the type I conformation, whereas ACM polymorphs and other cocrystals adopt the ACM type II conformation. Hydrogen-bond interactions in all the crystal structures were quantified by calculating their molecular electrostatic potential (MEP) surfaces. Hirshfeld surface analysis of the cocrystal surfaces shows that about 50% of the contribution is due to a combination of strong and weak O⋯H, N⋯H, Cl⋯H and C⋯H interactions. The physicochemical properties of these cocrystals are under study. PMID:28512568

Crystallization of a salt of a weak organic acid and base: solubility relations, supersaturation control and polymorphic behavior.

PubMed

Jones, H P; Davey, R J; Cox, B G

2005-03-24

Control of crystallization processes for organic salts is of importance to the pharmaceutical industry as many active pharmaceutical materials are marketed as salts. In this study, a method for estimating the solubility product of a salt of a weak acid and weak base from measured pH-solubility data is described for the first time. This allows calculation of the supersaturation of solutions at known pH. Ethylenediammonium 3,5-dinitrobenzoate is a polymorphic organic salt. A detailed study of the effects of pH, supersaturation, and temperature of crystallization on the physical properties of this salt shows that the desired polymorph may be produced by appropriate selection of the pH and supersaturation of crystallization. Crystal morphology is also controlled by these crystallization conditions.

Inkjet Printing Based Mono-layered Photonic Crystal Patterning for Anti-counterfeiting Structural Colors.

PubMed

Nam, Hyunmoon; Song, Kyungjun; Ha, Dogyeong; Kim, Taesung

2016-08-04

Photonic crystal structures can be created to manipulate electromagnetic waves so that many studies have focused on designing photonic band-gaps for various applications including sensors, LEDs, lasers, and optical fibers. Here, we show that mono-layered, self-assembled photonic crystals (SAPCs) fabricated by using an inkjet printer exhibit extremely weak structural colors and multiple colorful holograms so that they can be utilized in anti-counterfeit measures. We demonstrate that SAPC patterns on a white background are covert under daylight, such that pattern detection can be avoided, but they become overt in a simple manner under strong illumination with smartphone flash light and/or on a black background, showing remarkable potential for anti-counterfeit techniques. Besides, we demonstrate that SAPCs yield different RGB histograms that depend on viewing angles and pattern densities, thus enhancing their cryptographic capabilities. Hence, the structural colorations designed by inkjet printers would not only produce optical holograms for the simple authentication of many items and products but also enable a high-secure anti-counterfeit technique.

New 5-benzylidenethiazolidin-4-one inhibitors of bacterial MurD ligase: design, synthesis, crystal structures, and biological evaluation.

PubMed

Zidar, Nace; Tomašić, Tihomir; Šink, Roman; Kovač, Andreja; Patin, Delphine; Blanot, Didier; Contreras-Martel, Carlos; Dessen, Andréa; Premru, Manica Müller; Zega, Anamarija; Gobec, Stanislav; Mašič, Lucija Peterlin; Kikelj, Danijel

2011-11-01

Mur ligases (MurC-MurF), a group of bacterial enzymes that catalyze four consecutive steps in the formation of cytoplasmic peptidoglycan precursor, are becoming increasingly adopted as targets in antibacterial drug design. Based on the crystal structure of MurD cocrystallized with thiazolidine-2,4-dione inhibitor I, we have designed, synthesized, and evaluated a series of improved glutamic acid containing 5-benzylidenerhodanine and 5-benzylidenethiazolidine-2,4-dione inhibitors of MurD with IC(50) values up to 28 μM. Inhibitor 37, with an IC(50) of 34 μM, displays a weak antibacterial activity against S. aureus ATCC 29213 and E. faecalis ATCC 29212 with minimal inhibitory concentrations of 128 μg/mL. High-resolution crystal structures of MurD in complex with two new inhibitors (compounds 23 and 51) reveal details of their binding modes within the active site and provide valuable information for further structure-based optimization. Copyright © 2011 Elsevier Masson SAS. All rights reserved.

Inkjet Printing Based Mono-layered Photonic Crystal Patterning for Anti-counterfeiting Structural Colors

NASA Astrophysics Data System (ADS)

Nam, Hyunmoon; Song, Kyungjun; Ha, Dogyeong; Kim, Taesung

2016-08-01

Photonic crystal structures can be created to manipulate electromagnetic waves so that many studies have focused on designing photonic band-gaps for various applications including sensors, LEDs, lasers, and optical fibers. Here, we show that mono-layered, self-assembled photonic crystals (SAPCs) fabricated by using an inkjet printer exhibit extremely weak structural colors and multiple colorful holograms so that they can be utilized in anti-counterfeit measures. We demonstrate that SAPC patterns on a white background are covert under daylight, such that pattern detection can be avoided, but they become overt in a simple manner under strong illumination with smartphone flash light and/or on a black background, showing remarkable potential for anti-counterfeit techniques. Besides, we demonstrate that SAPCs yield different RGB histograms that depend on viewing angles and pattern densities, thus enhancing their cryptographic capabilities. Hence, the structural colorations designed by inkjet printers would not only produce optical holograms for the simple authentication of many items and products but also enable a high-secure anti-counterfeit technique.

The electronic structure of RbTiOPO4 and the effects of the A-site cation substitution in KTiOPO4-family crystals

NASA Astrophysics Data System (ADS)

Atuchin, V. V.; Kesler, V. G.; Meng, Guangsi; Lin, Z. S.

2012-10-01

The electronic structure of RbTiOPO4 has been investigated with x-ray photoemission spectroscopy. Detailed photoemission spectra of the element core levels have been recorded under excitation by nonmonochromatic Al Kα radiation (1486.6 eV). The chemical bonding parameters are compared to those reported for complex titanates and phosphates. The band structures of KTiOPO4, RbTiOPO4, K0.535R0.465TiOPO4 and TlTiOPO4 have been calculated by ab initio methods and compared to available experimental results. It is found that the band structure of KTP-type phosphate crystals is weakly dependent on the nature of the A-site (A=K, Rb, Tl) element.

Chiral discrimination in diastereomeric salts of chlorine-substituted mandelic acid and phenylethylamine.

PubMed

He, Quan; Gomaa, Hassan; Rohani, Sohrab; Zhu, Jesse; Jennings, Michael

2010-08-01

The crystal structures of diastereomeric salts of chloromandelic acid and phenylethylamine were determined and are presented herein. The structure comparison between less soluble salts and more soluble salts shows that weak interactions such as CH/pi interactions and van der Waals gain importance and contribute to chiral recognition when the hydrogen bonding patterns are very similar. Copyright 2010 Wiley-Liss, Inc.

Three-dimensional six-connecting organic building blocks based on polychlorotriphenylmethyl units--synthesis, self-assembly, and magnetic properties.

PubMed

Roques, Nans; Maspoch, Daniel; Wurst, Klaus; Ruiz-Molina, Daniel; Rovira, Concepció; Veciana, Jaume

2006-12-13

The synthesis of a three-dimensional, six-connecting, organic building block based on a robust, rigid, and open-shell polychlorotriphenylmethyl (PTM) unit (radical 1) is reported, and its self-assembly properties are described in detail. The tendencies of this highly polar molecule and its hydrogenated precursor, compound 4, to form hydrogen bonds with oxygenated solvents ([1THF(6)] and [4THF(6)]) were reduced by replacing THF with diethyl ether in the crystallization process to yield two-dimensional (2D) hydrogen-bonded structures ([1(Et(2)O)(3)] and [4(Et(2)O)(3)]). The presence of direct hydrogen bonds between the radicals in the latter phase of 1 gives rise to very weak ferromagnetic intermolecular interactions at low temperatures, whereas when the radicals are isolated by THF molecules these interactions are antiferromagnetic and very weak. The role played by the carboxylic groups not only in the self-assembly properties but also in the transmission of the magnetic interactions has been illustrated by determination of the crystal structure and measurement of the magnetic properties of the corresponding hexaester radical 6, in which the close packing of molecular units gives rise to weak antiferromagnetic intermolecular interactions. Attempts to avoid solvation of the molecules in the solid state and to increase the structural and magnetic dimensionality were pursued by recrystallization of both compounds 1 and 4 from concentrated nitric acid, affording two three-dimensional (3D) robust hydrogen-bonded structures. While the structure obtained with compound 4 is characterized by the presence of polar channels and boxes containing water guest molecules along the c axis, radical 1 was oxidized to the corresponding fuchsone 10, which presented a completely different close-packed, guest-free structure.

Cubic-to-tetragonal structural phase transition in Rb{sub 1{minus}x}Cs{sub x}CaF{sub 3} solid solutions: Thermal expansion and EPR studies

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lahoz, F.; Villacampa, B.; Alcala, R.

1997-04-01

The influence of crystal mixing on the structural phase transitions in Rb{sub 1{minus}x}Cs{sub x}CaF{sub 3} (0{lt}x{lt}1) fluoroperovskite crystals has been studied by thermal expansion and EPR measurements of Ni{sup 2+} and Ni{sup 3+} paramagnetic probes. A cubic-to-tetragonal phase transition has been detected in crystals with x=0, 0.1, 0.21, 0.27, and 0.35. The critical temperature and the tetragonal distortion decrease as x increases. No transition was observed for x{ge}0.44. This transition shows a weak first-order component in the x=0 and 0.1 samples, which is progressively smeared out for x{gt}0.1, indicating a spatial distribution of the critical temperature in those crystals withmore » high ionic substitution rate. In RbCaF{sub 3}, another structural phase transition was observed at 20 K with a thermal hysteresis between 20 and 40 K. This transition has not been found in any of the mixed crystals.« less

Identification of N-ethylmethylamine as a novel scaffold for inhibitors of soluble epoxide hydrolase by crystallographic fragment screening.

PubMed

Amano, Yasushi; Tanabe, Eiki; Yamaguchi, Tomohiko

2015-05-15

Soluble epoxide hydrolase (sEH) is a potential target for the treatment of inflammation and hypertension. X-ray crystallographic fragment screening was used to identify fragment hits and their binding modes. Eight fragment hits were identified via soaking of sEH crystals with fragment cocktails, and the co-crystal structures of these hits were determined via individual soaking. Based on the binding mode, N-ethylmethylamine was identified as a promising scaffold that forms hydrogen bonds with the catalytic residues of sEH, Asp335, Tyr383, and Tyr466. Compounds containing this scaffold were selected from an in-house chemical library and assayed. Although the starting fragment had a weak inhibitory activity (IC50: 800μM), we identified potent inhibitors including 2-({[2-(adamantan-1-yl)ethyl]amino}methyl)phenol exhibiting the highest inhibitory activity (IC50: 0.51μM). This corresponded to a more than 1500-fold increase in inhibitory activity compared to the starting fragment. Co-crystal structures of the hit compounds demonstrate that the binding of N-ethylmethylamine to catalytic residues is similar to that of the starting fragment. We therefore consider crystallographic fragment screening to be appropriate for the identification of weak but promising fragment hits. Copyright © 2015 Elsevier Ltd. All rights reserved.

Preparation, characterization and crystal structures of three salts of the quaterpyridine ligand

NASA Astrophysics Data System (ADS)

Ciesielski, Artur; Stefankiewicz, Artur R.; Patroniak, Violetta; Kubicki, Maciej

2009-07-01

As a result of a reaction between 6,6'''-dimethyl-2,2':6',2'':6'',2'''-quaterpyridine C 22H 18N 4 and lanthanide(III) salts, compounds, [C 22H 20N 4] 2+·2(CF 3SO 3) - ( 1) and [C 22H 20N 4] 2+·2(ClO 4) - ( 2), have been obtained. They were characterized by spectroscopic techniques (ESI-MS, NMR, IR), elemental analysis, and their formulae were confirmed on the basis of X-ray crystallography. It turned out that the perchlorate crystallizes as two solvates: with acetonitrile and disordered water molecules. These are the first structural characterization of a 6,6'″-dimethyl-2,2':6',2″:6″,2'″-quaterpyridinium dication. Due to the intramolecular hydrogen bond it adopts the previously unobserved cis/trans/cis conformation. In all three crystals the dications have C i symmetry, they occupy the special positions in their respective space groups. In the crystal structures the π-π stacking and weak hydrogen bonds add directionality to the dominating electrostatic interactions between cations and anions.

Synthesis, structural characterization, and DFT calculations of 3-buthyl-4-(3-methyl-3-mesitylcyclobut-1-yl)-1,3-thiazole-2(3H)-thione

DOE Office of Scientific and Technical Information (OSTI.GOV)

Şen, B.; Barim, E.; Kirilmis, C.

2016-03-15

The title compound, C{sub 21}H{sub 29}NS{sub 2}, has been synthesized and its crystal structure has been determined from single crystal X-ray diffraction data. Crystals are monoclinic, a = 11.4923(8), b = 13.1842(7), c = 14.6583(8) Å, β = 109.983(6)°, sp. gr. P2{sub 1}/c, Z = 4. Mesityl and thiazole groups are in cis positions with respect to the cyclobutane ring. The cyclobutane ring is puckered, with a dihedral angle of 26.6(2)° between the two three-atom planes. The crystal structure involves one weak intermolecular C–H···S hydrogen-bond. The molecular geometry was also optimized using density functional theory (DFT/B3LYP) method with the 6-311G(d,more » p) basis set in ground state. Geometric parameters (bond lengths, bond angles and torsion angles) and vibrational assignments have been calculated theoretically and compared with the experimental data.« less

One pot synthesis of two Mn(II) perchlorate complexes with s-triazine NNN-pincer ligand; molecular structure, Hirshfeld analysis and DFT studies

NASA Astrophysics Data System (ADS)

Soliman, Saied M.; El-Faham, Ayman

2018-07-01

Self assembly of Mn(II) perchlorate and bis(pyrazolo)-s-triazine pincer ligand (L) in methanol-water mixture afforded the homoleptic [MnL2](ClO4)2 complex (1) as plate colorless crystals. Following the crystallization process till the near dryness of the solution, we noted few needle like crystals of the heteroleptic [MnL(H2O)3](ClO4)2·H2O complex (2). Their molecular and supramolecular structures were analyzed using single crystal structure combined with Hirshfeld analysis. The packing of complexes 1 and 2 is dominated by weak Csbnd H⋯O and strong Osbnd H⋯O hydrogen bonds, respectively, as well as anion-π stacking interactions. Using Hirshfeld analysis, the percentages of the O⋯H intermolecular contacts are 32.7% and 36.8% for 1 and 2, respectively. The Mnsbnd N distances correlated well with the atoms in molecules (AIM) topological parameters. The amount of electron density transferred from the ligand units to the manganese centre are nearly the same (0.9 e) in both complexes.

Crystal structure of (7-methyl-2-oxo-2H-chromen-4-yl)methyl piperidine-1-carbo­di­thio­ate

PubMed Central

Roopashree, K. R.; Meenakshi, T. G.; Kumar, K. Mahesh; Kotresh, O.; Devarajegowda, H. C.

2015-01-01

In the title compound, C17H19NO2S2, the 2H-chromene ring system is nearly planar, with a maximum deviation of 0.0383 (28) Å, and the piperidine ring adopts a chair conformation. The 2H-chromene ring makes dihedral angles of 32.89 (16) and 67.33 (8)°, respectively, with the mean planes of the piperidine ring and the carbodi­thio­ate group. In the crystal, C—H⋯O and weak C—H⋯S hydrogen bonds link the mol­ecules into chains along [001]. The crystal structure also features C—H⋯π and π–π inter­actions, with a centroid–centroid distance of 3.7097 (17) Å. PMID:26396821

Global low-energy weak solution and large-time behavior for the compressible flow of liquid crystals

NASA Astrophysics Data System (ADS)

Wu, Guochun; Tan, Zhong

2018-06-01

In this paper, we consider the weak solution of the simplified Ericksen-Leslie system modeling compressible nematic liquid crystal flows in R3. When the initial data are of small energy and initial density is positive and essentially bounded, we prove the existence of a global weak solution in R3. The large-time behavior of a global weak solution is also established.

Optical characteristics of novel bulk and nanoengineered laser host materials

NASA Astrophysics Data System (ADS)

Prasad, Narasimha S.; Sova, Stacey; Kelly, Lisa; Bevan, Talon; Arnold, Bradley; Cooper, Christopher; Choa, Fow-Sen; Singh, N. B.

2018-02-01

The hexagonal apatite single crystals have been investigated for their applications as laser host materials. Czochralksi and flux growth methods have been utilized to obtain single crystals. For low temperature processing (<100 0C), several techniques for crystal growth have been developed. The hexagonal apatite structure (space group P63/m) is characteristic of several compounds, some of which have extremely interesting and useful properties as laser hosts and bone materials. Calcium lanthanum silicate (Nd-doped) and lanthanum aluminate material systems were studied in detail. Nanoengineered calcium and lanthanum based silicates were synthesized by a solution method and their optical and morphological characteristics were compared with Czochralski grown bulk hydroxyapatite single crystals. Materials were evaluated by absorbance, fluorescence and Raman characteristics. Neodymium, iron and chromium doped crystals grown by a solution method showed weak but similar optical properties to that of Czochralski grown single crystals.

Band structure of an electron in a kind of periodic potentials with singularities

NASA Astrophysics Data System (ADS)

Hai, Kuo; Yu, Ning; Jia, Jiangping

2018-06-01

Noninteracting electrons in some crystals may experience periodic potentials with singularities and the governing Schrödinger equation cannot be defined at the singular points. The band structure of a single electron in such a one-dimensional crystal has been calculated by using an equivalent integral form of the Schrödinger equation. Both the perturbed and exact solutions are constructed respectively for the cases of a general singular weak-periodic system and its an exactly solvable version, Kronig-Penney model. Any one of them leads to a special band structure of the energy-dependent parameter, which results in an effective correction to the previous energy-band structure and gives a new explanation for forming the band structure. The used method and obtained results could be a valuable aid in the study of energy bands in solid-state physics, and the new explanation may trigger investigation to different physical mechanism of electron band structures.

Super-resolution biomolecular crystallography with low-resolution data.

PubMed

Schröder, Gunnar F; Levitt, Michael; Brunger, Axel T

2010-04-22

X-ray diffraction plays a pivotal role in the understanding of biological systems by revealing atomic structures of proteins, nucleic acids and their complexes, with much recent interest in very large assemblies like the ribosome. As crystals of such large assemblies often diffract weakly (resolution worse than 4 A), we need methods that work at such low resolution. In macromolecular assemblies, some of the components may be known at high resolution, whereas others are unknown: current refinement methods fail as they require a high-resolution starting structure for the entire complex. Determining the structure of such complexes, which are often of key biological importance, should be possible in principle as the number of independent diffraction intensities at a resolution better than 5 A generally exceeds the number of degrees of freedom. Here we introduce a method that adds specific information from known homologous structures but allows global and local deformations of these homology models. Our approach uses the observation that local protein structure tends to be conserved as sequence and function evolve. Cross-validation with R(free) (the free R-factor) determines the optimum deformation and influence of the homology model. For test cases at 3.5-5 A resolution with known structures at high resolution, our method gives significant improvements over conventional refinement in the model as monitored by coordinate accuracy, the definition of secondary structure and the quality of electron density maps. For re-refinements of a representative set of 19 low-resolution crystal structures from the Protein Data Bank, we find similar improvements. Thus, a structure derived from low-resolution diffraction data can have quality similar to a high-resolution structure. Our method is applicable to the study of weakly diffracting crystals using X-ray micro-diffraction as well as data from new X-ray light sources. Use of homology information is not restricted to X-ray crystallography and cryo-electron microscopy: as optical imaging advances to subnanometre resolution, it can use similar tools.

Nontypical iodine–halogen bonds in the crystal structure of (3 E )-8-chloro-3-iodomethylidene-2,3-dihydro-1,4-oxazino[2,3,4- ij ]quinolin-4-ium triiodide

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bartashevich, E. V.; Batalov, V. I.; Yushina, I. D.

2016-03-23

Two kinds of iodine–iodine halogen bonds are the focus of our attention in the crystal structure of the title salt, C 12H 8ClINO +·I 3 -, described by X-ray diffraction. The first kind is a halogen bond, reinforced by charges, between the I atom of the heterocyclic cation and the triiodide anion. The second kind is the rare case of a halogen bond between the terminal atoms of neighbouring triiodide anions. The influence of relatively weakly bound iodine inside an asymmetric triiodide anion on the thermal and Raman spectroscopic properties has been demonstrated.

2-[4-(4,5-Dihydro-1H-pyrrol-2-yl)phen­yl]-4,5-dihydro-1H-imidazole

PubMed Central

Kia, Reza; Fun, Hoong-Kun; Kargar, Hadi

2008-01-01

The mol­ecule of the title compound, C12H14N4, lies about a crystallographic inversion centre. The five- and six-membered rings are twisted from each other, forming a dihedral angle of 18.06 (7)°. In the crystal structure, neighbouring mol­ecules are linked by inter­molecular N—H⋯N hydrogen bonds into one-dimensional infinite chains forming 18-membered rings with R 2 2(18) motifs. The crystal structure is further stabilized by weak inter­molecular π–π stacking [centroid–centroid distance = 3.8254 (6) Å] and C—H⋯π inter­actions. PMID:21581375

Er{sub 1.33}Pt{sub 3}Ga{sub 8}: A modulated variant of the Er{sub 4}Pt{sub 9}Al{sub 24}-structure type

DOE Office of Scientific and Technical Information (OSTI.GOV)

Oswald, Iain W.H.; Gourdon, Olivier; Bekins, Amy

Single crystals of Er{sub 1.33}Pt{sub 3}Ga{sub 8} were synthesized in a molten Ga flux. Er{sub 1.33}Pt{sub 3}Ga{sub 8} can be considered to be a modulated variant of the Er{sub 4}Pt{sub 9}Al{sub 24}-structure type, where the partial occupancies are ordered. Indeed, the presence of weak satellite reflections indicates a complex organization and distribution of the Er and Ga atoms within the [ErGa] slabs. The structure has been solved based on single crystal X-ray diffraction data in the monoclinic superspace group X2/m(0β0)00 with a commensurate modulated vector q=1/3b*. Precession images also indicate diffusion in the perpendicular direction indicating a partial disorder ofmore » this arrangement from layer to layer. In addition, Er{sub 1.33}Pt{sub 3}Ga{sub 8} shows antiferromagnetic ordering at T{sub N}~5 K. - Graphical abstract: A precession image of the hk0 zone showing weak, periodic, unindexed reflections indicating modulation and representation of the commensurate [ErGa] layer showing the waving modulated occupation. - Highlights: • Single crystals of Er{sub 1.33}Pt{sub 3}Ga{sub 8} were grown from gallium flux. • The structure of Er{sub 1.33}Pt{sub 3}Ga{sub 8} is compared to Er{sub 4}Pt{sub 9}Al{sub 24}. • Structure has been solved in the monoclinic superspace group X2/m(0β0)00 with a commensurate modulated vector q=1/3b*.« less

(Z)-3-(1-Chloro-prop-1-en-yl)-2-methyl-1-phenyl-sulfonyl-1H-indole.

PubMed

Umadevi, M; Saravanan, V; Yamuna, R; Mohanakrishnan, A K; Chakkaravarthi, G

2013-11-16

In the title compound, C18H16ClNO2S, the indole ring system forms a dihedral angle of 75.07 (8)° with the phenyl ring. The mol-ecular structure is stabilized by a weak intra-molecular C-H⋯O hydrogen bond. In the crystal, mol-ecules are linked by weak C-H⋯O hydrogen bonds, forming a chain along [10-1]. C-H⋯π inter-actions are also observed, leading to a three-dimensional network.

A structural analysis of small vapor-deposited 'multiply twinned' gold particles

NASA Technical Reports Server (NTRS)

Yang, C. Y.; Heinemann, K.; Yacaman, M. J.; Poppa, H.

1979-01-01

High resolution selected zone dark field, Bragg reflection imaging and weak beam dark field techniques of transmission electron microscopy were used to determine the structure of small gold particles vapor deposited on NaCl substrates. Attention was focused on the analysis of those particles in the 50-150 A range that have pentagonal or hexagonal bright field profiles. These particles have been previously described as multiply twinned crystallites composed of face-centered cubic tetrahedra. The experimental evidence of the present studies can be interpreted on the assumption that the particle structure is a regular icosahedron or decahedron for the hexagonal or the pentagonal particles respectively. The icosahedron is a multiply twinned rhombohedral crystal and the decahedron is a multiply twinned body-centered orthorhombic crystal, each of which constitutes a slight distortion from the face-centered cubic structure.

Supramolecular assemblies of tetrafluoroterephthalic acid and N-heterocycles via various strong hydrogen bonds and weak Csbnd H⋯F interactions: Synthons cooperation, robust motifs and structural diversity

NASA Astrophysics Data System (ADS)

Hu, Yanjing; Hu, Hanbin; Li, Yingying; Chen, Ruixin; Yang, Yu; Wang, Lei

2016-10-01

A series of organic solid states including three salts, two co-crystals, and three hydrates based on tetrafluoroterephthalic acid (H2tfBDC) and N-bearing ligands (2,4-(1H,3H)-pyrimidine dione (PID), 2,4-dihydroxy-6-methyl pyrimidine (DHMPI), 2-amino-4,6-dimethyl pyrimidine (ADMPI), 2-amino-4,6-dimenthoxy pyrimidine (ADMOPI), 5,6-dimenthyl benzimidazole (DMBI), 2-aminobenzimidazole (ABI), 3,5-dimethyl pyrazole (DMP), and 3-cyanopyridine (3-CNpy)), namely, [(PID)2·(H2tfBDC)] (1), [(DHMPI)2·(H2tfBDC)] (2), [(H-ADMPI+)2·(tfBDC2-)·2(H2O)] (3), [(H-ADMOPI+)2·(tfBDC2-)·(H2O)] (4), [(H-DMBI+)2·(tfBDC2-)·2(H2O)] (5), [(H-ABI+)2·(tfBDC2-)] (6), [(H-DMP+)·(HtfBDC-)] (7), and [(H-3-CNpy+)·(HtfBDC-)] (8), were synthesized by solvent evaporation method. Crystal structures analyses show that the F atom of the H2tfBDC participates in multiple Csbnd H⋯F hydrogen bond formations, producing different supramolecular synthons. The weak hydrogen bonding Csbnd H⋯F and Nsbnd H⋯F play an important part in constructing the diversity structures 2-8, except in crystal 1. In complexes 1-3, they present the same synthon R22(8) with different N-heterocyclic compounds, which may show the strategy in constructing the supramolecular. Meanwhile, the complex 3 exhibits a 2D layer, and the independent molecules of water exist in the adjacent layers. In complexes 4 and 5, the water molecules connect the neighboring layers to form 3D network by strong Osbnd H⋯O hydrogen bonding. These crystals 1-8 were fully characterized by single-crystal X-ray crystallography, elemental analysis, infrared spectroscopy (IR), and thermogravimetric analysis (TGA).

Photoemission study of the electronic structure and charge density waves of Na₂Ti₂Sb₂O

DOE PAGES

Tan, S. Y.; Jiang, J.; Ye, Z. R.; ...

2015-04-30

The electronic structure of Na₂Ti₂Sb₂O single crystal is studied by photon energy and polarization dependent angle-resolved photoemission spectroscopy (ARPES). The obtained band structure and Fermi surface agree well with the band structure calculation of Na₂Ti₂Sb₂O in the non-magnetic state, which indicates that there is no magnetic order in Na₂Ti₂Sb₂O and the electronic correlation is weak. Polarization dependent ARPES results suggest the multi-band and multi-orbital nature of Na₂Ti₂Sb₂O. Photon energy dependent ARPES results suggest that the electronic structure of Na₂Ti₂Sb₂O is rather two-dimensional. Moreover, we find a density wave energy gap forms below the transition temperature and reaches 65 meV atmore » 7 K, indicating that Na₂Ti₂Sb₂O is likely a weakly correlated CDW material in the strong electron-phonon interaction regime. (author)« less

Synthesis, structure, computational and in-silico anticancer studies of N,N-diethyl-N‧-palmitoylthiourea

NASA Astrophysics Data System (ADS)

Asegbeloyin, Jonnie Niyi; Oyeka, Ebube Evaristus; Okpareke, Obinna; Ibezim, Akachukwu

2018-02-01

A new potential ONS donor ligand N,N-diethyl-N‧-palmitoylthiourea (PACDEA) with the molecular formular C21H42N2OS has been synthesized and characterized by ESI-MS, UV, FTIR 1H and 13C NMR spectroscopy and single X-ray crystallography. The asymmetric molecules crystallized in the centrosymmetric structure of monoclinic crystal system with space group P21/c. In the crystal structure of the compound, molecules are linked in a continuous chain by intermolecular Nsbnd H⋯Odbnd C hydrogen bonds, which stabilized the crystal structure. The palmitoyl moiety and N (2)-ethyl group lie on a plane, while the thiocarbonyl moiety is twisted and lying othorgonal to the plane. Non-covalent interaction (NCI) analysis on the hydrogen bonded solid state structure of the molecule revealed the presence of a significant number of non-covalent interactions including intermolecular hydrogen bonding interactions, Csbnd Hsbnd -lone pair interactions, weak Van der Waals interactions, and steric/ring closure interactions. The NCI analysis also showed the presence of intramolecular stabilizing Csbnd H⋯Odbnd C and Csbnd H⋯Sdbnd C interactions. Docking simulation revealed that the compound interacted favourably with ten selected validated anticancer drug targets, which is an indication that the compound could possess some anticancer properties.

Superconductivity and valence state in layered single-crystal HfAs1.67Te0.12

NASA Astrophysics Data System (ADS)

Peng, Jian; Yu, Jia; Zhang, Shuai; Chen, Genfu

2018-01-01

We report a detailed study on single crystals of HfAs1.67Te0.12 within a PbFCl-type layered structure. The single crystals of the title compound were successfully grown using a chemical transport reaction. The temperature dependence of electrical resistivity ρ (T), AC magnetic susceptibility {χ }{AC}(T) and specific heat C(T) show a bulk superconductivity with transition temperature T c = 1.67 K. The jump of C/T at T c is comparable to the traditional BCS weak-coupling model. A full H-T phase diagram is established using the results of ρ (T,H) and C(T) under fields, suggesting a rather weak anisotropy [({H}c2\\parallel {ab}(0)/{H}c2\\parallel c(0)] of 1.8 in orbital limit dominated three-dimension-like superconducting system. The mixed-valence states of Hf and As observed in the binding energy from x-ray photoelectron spectroscopy are consistent with the single-crystal x-ray diffraction analysis, indicating that the As-Te disorder prefers to occur in the [HfAs] layer and a large amount of vacancies are present in tetragonal As layer. As compared to HfAs1.7Se0.2 (T c = 0.52 K), a positive-like vacancy effect on T c has been confirmed in HfAs1.67Te0.12. The analysis of the Hall coefficient implies that the hole-type carriers dominate the transport properties, which is in good agreement with the hole pockets at Fermi surface obtained in a band structure calculation. The detailed study of single-crystal HfAs1.67Te0.12 provides a possible candidate to discuss the non-magnetic Kondo effect.

2-Phenyl-4,5-di-2-pyridyl-1H-imidazole

PubMed Central

Felsmann, Marika; Schindler, Diana; Weber, Edwin

2010-01-01

In the title compound, C19H14N4, which was crystallized from dimethyl sulfoxide, the arene and heterocyclic rings of the lophine analogue framework differ only slightly from coplanarity (dihedral angles range from 8.8 to 20.2°), and intramolecular N—H⋯N and C—H⋯N interactions help to establish the conformation. The crystal packing features a number of weak C—H⋯N, N—H⋯N hydrogen-bond type contacts, and C—H⋯π interactions, leading to the formation of a herringbone structure. PMID:21580039

Crystal structure of fenclorim.

PubMed

Kwon, Eunjin; Kim, Jineun; Kang, Gihaeng; Kim, Tae Ho

2015-10-01

In the title compound, C10H6Cl2N2 (systematic name: 4,6-di-chloro-2-phenyl-pyrimidine), which is used commercially as the herbicide safener, fenclorim, the dihedral angle between the di-chloro-pyrimidyl and phenyl rings is 9.45 (10)°. In the crystal, C-H⋯N hydrogen bonds link adjacent mol-ecules, forming chains along the c-axis direction. In addition, weak inter-molecular C-Cl⋯π [3.6185 (10) Å] and π-π [3.8796 (11) Å] inter-actions are present, forming a three-dimensional network.

Deformation Mechanism and Recrystallization Relationships in Galfenol Single Crystals: On the Origin of Goss and Cube Orientations

NASA Astrophysics Data System (ADS)

Na, Suok-Min; Smith, Malcolm; Flatau, Alison B.

2018-06-01

In this work, deformation mechanism related to recrystallization behavior in single-crystal disks of Galfenol (Fe-Ga alloy) was investigated to gain insights into the influence of crystal orientations on structural changes and selective grain growth that take place during secondary recrystallization. We started with the three kinds of single-crystal samples with (011)[100], (001)[100], and (001)[110] orientations, which were rolled and annealed to promote the formation of different grain structures and texture evolutions. The initial Goss-oriented (011)[100] crystal mostly rotated into {111}<112> orientations with twofold symmetry and shear band structures by twinning resulted in the exposure of rolled surface along {001}<110> orientation during rolling. In contrast, the Cube-oriented (001)[100] single crystal had no change in texture during rolling with the thickness reduction up to 50 pct. The {123}<111> slip systems were preferentially activated in these single crystals during deformation as well as {112}<111> slip systems that are known to play a role in primary slip of body-centered cubic (BCC) materials such as α-iron and Fe-Si alloys. After annealing, the deformed Cube-oriented single crystal had a small fraction (<10 pct) of recrystallized Goss-oriented grains. The weak Goss component remained in the shear bands of the 50 pct rolled Goss-oriented single crystal, and it appeared to be associated with coalescence of subgrains inside shear band structures during primary recrystallization. Rolling of the (001)[110] single crystal led to the formation of a tilted (001)[100] component close to the <120> orientation, associated with {123}<111> slip systems as well. This was expected to provide potential sites of nucleation for secondary recrystallization; however, no Goss- and Cube-oriented components actually developed in this sample during secondary recrystallization. Those results illustrated how the recrystallization behavior can be influenced by deformed structure and the slip systems.

Crystal structures of three 3-chloro-3-methyl-2,6-di­aryl­piperidin-4-ones

PubMed Central

Arulraj, R.; Sivakumar, S.; Kaur, Manpreet; Jasinski, Jerry P.

2017-01-01

The syntheses and crystal structure of 3-chloro-3-methyl-r-2,c-6-di­phenyl­piperidin-4-one, C18H18ClNO, (I), 3-chloro-3-methyl-r-2,c-6-di-p-tolyl­piperidin-4-one, C20H22ClNO, (II), and 3-chloro-3-methyl-r-2,c-6-bis­(4-chloro­phen­yl)piperidin-4-one, C18H16Cl3NO, (III), are described. In each structure, the piperidine ring adopts a chair conformation and dihedral angles between the mean planes of the phenyl rings are 58.4 (2), 73.5 (5) and 78.6 (2)° in (I), (II) and (III), respectively. In the crystals, mol­ecules are linked into C(6) chains by weak N—H⋯O hydrogen bonds and C—H⋯π inter­actions are also observed. PMID:28217321

Novel Co(III)/Co(II) mixed valence compound [Co(bapen)Br2]2[CoBr4] (bapen = N,N‧-bis(3-aminopropyl)ethane-1,2-diamine): Synthesis, crystal structure and magnetic properties

NASA Astrophysics Data System (ADS)

Smolko, Lukáš; Černák, Juraj; Kuchár, Juraj; Miklovič, Jozef; Boča, Roman

2016-09-01

Green crystals of Co(III)/Co(II) mixed valence compound [Co(bapen)Br2]2[CoBr4] (bapen = N,N‧-bis(3-aminopropyl)ethane-1,2-diamine) were isolated from the aqueous system CoBr2 - bapen - HBr, crystallographically studied and characterized by elemental analysis and IR spectroscopy. Its ionic crystal structure is built up of [Co(bapen)Br2]+ cations and [CoBr4]2- anions. The Co(III) central atoms within the complex cations are hexacoordinated (donor set trans-N4Br2) with bromido ligands placed in the axial positions. The Co(II) atoms exhibit distorted tetrahedral coordination. Beside ionic forces weak Nsbnd H⋯Br intermolecular hydrogen bonding interactions contribute to the stability of the structure. Temperature variable magnetic measurements confirm the S = 3/2 behavior with the zero-field splitting of an intermediate strength: D/hc = 8.7 cm-1.

Crystal structure of 3-{1′-[3,5-bis­(tri­fluoro­meth­yl)phen­yl]ferrocenyl}-4-bromo­thio­phene

PubMed Central

Poppitz, Elisabeth A.; Korb, Marcus; Lang, Heinrich

2014-01-01

The mol­ecular structure of the title compound, [Fe(C9H6BrS)(C13H7F6)], consists of a ferrocene backbone with a bis­(tri­fluoro­meth­yl)phenyl group at one cyclo­penta­dienyl ring and a thio­phene heterocycle at the other cyclo­penta­dienyl ring. The latter is disordered over two sets of sites in a 0.6:0.4 ratio. In the crystal structure, intra­molecular π–π inter­actions between the thienyl and the phenyl substituent [centroid–centroid distance 3.695 (4) Å] and additional weak T-shaped π–π inter­actions between the thienyl and the phenyl-substituted cyclo­penta­dienyl ring [4.688 (6) Å] consolidate the crystal packing. PMID:25484662

Growth and characterization of Na2Mo2O7 crystal scintillators for rare event searches

NASA Astrophysics Data System (ADS)

Pandey, Indra Raj; Kim, H. J.; Kim, Y. D.

2017-12-01

Disodium dimolybdate (Na2Mo2O7) crystals were grown using the Czochralski technique. The thermal characteristics of the compound were analyzed using thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) measurements. The crystal structure of the grown sample was confirmed using X-ray diffraction (XRD). Luminescence properties were measured at room and low temperatures, using a light emitting diode (LED) source. Very weak luminescence was observed at room temperature; however, the luminescence intensity was enhanced at low temperatures. The crystal's transmittance spectrum was measured for estimating its optical quality and energy band gap. The grown crystal exhibited a luminescence light yield of 55% compared with CaMoO4 crystals at 10 K, when excited by a 280-nm-wavelength LED source, but does not have the drawbacks of radioactive Ca isotopes. These results suggest that at cryogenic temperatures, Na2Mo2O7 crystal scintillators are promising for the detection of dark matter and neutrinoless double beta decay of 100Mo.

Rapid assessment of crystal orientation in semi-crystalline polymer films using rotational zone annealing and impact of orientation on mechanical properties

DOE PAGES

Ye, Changhuai; Wang, Chao; Wang, Jing; ...

2017-08-17

Crystal orientation in semi-crystalline polymers tends to enhance their performance, such as increased yield strength and modulus, along the orientation direction. Zone annealing (ZA) orients the crystal lamellae through a sharp temperature gradient that effectively directs the crystal growth, but the sweep rate (V ZA) of this gradient significantly impacts the extent of crystal orientation. Here in this work, we demonstrate rotational zone annealing (RZA) as an efficient method to elucidate the influence of V ZA on the crystal morphology of thin films in a single experiment using isotactic poly(1-butene), PB-1, as a model semi-crystalline polymer. These RZA results aremore » confirmed using standard, serial linear ZA to tune the structure from an almost unidirectional oriented morphology to weakly oriented spherulites. The overall crystallinity is only modestly changed in comparison to isothermal crystallization (maximum of 55% from ZA vs. 48% for isothermal crystallization). However, the average grain size increases and the spherulites become anisotropic from ZA. Due to these structural changes, the Young's modulus of the oriented films, both parallel and perpendicular to the spherulite orientation direction, is significantly increased by ZA. The modulus does become anisotropic after ZA due to the directionality in the crystal structure, with more than a threefold increase in the modulus parallel to the orientation direction for the highest oriented film in comparison to the modulus from isothermal crystallization. Lastly, RZA enables rapid identification of conditions to maximize orientation of crystals in thin polymer films, which could find utility in determining conditions to improve crystallinity and performance in organic electronics.« less

Rapid assessment of crystal orientation in semi-crystalline polymer films using rotational zone annealing and impact of orientation on mechanical properties

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ye, Changhuai; Wang, Chao; Wang, Jing

Crystal orientation in semi-crystalline polymers tends to enhance their performance, such as increased yield strength and modulus, along the orientation direction. Zone annealing (ZA) orients the crystal lamellae through a sharp temperature gradient that effectively directs the crystal growth, but the sweep rate (V ZA) of this gradient significantly impacts the extent of crystal orientation. Here in this work, we demonstrate rotational zone annealing (RZA) as an efficient method to elucidate the influence of V ZA on the crystal morphology of thin films in a single experiment using isotactic poly(1-butene), PB-1, as a model semi-crystalline polymer. These RZA results aremore » confirmed using standard, serial linear ZA to tune the structure from an almost unidirectional oriented morphology to weakly oriented spherulites. The overall crystallinity is only modestly changed in comparison to isothermal crystallization (maximum of 55% from ZA vs. 48% for isothermal crystallization). However, the average grain size increases and the spherulites become anisotropic from ZA. Due to these structural changes, the Young's modulus of the oriented films, both parallel and perpendicular to the spherulite orientation direction, is significantly increased by ZA. The modulus does become anisotropic after ZA due to the directionality in the crystal structure, with more than a threefold increase in the modulus parallel to the orientation direction for the highest oriented film in comparison to the modulus from isothermal crystallization. Lastly, RZA enables rapid identification of conditions to maximize orientation of crystals in thin polymer films, which could find utility in determining conditions to improve crystallinity and performance in organic electronics.« less

Multicomponent hydrogen-bonding organic solids constructed from 6-hydroxy-2-naphthoic acid and N-heterocycles: Synthesis, structural characterization and synthon discussion

NASA Astrophysics Data System (ADS)

Zong, Yingxia; Shao, Hui; Pang, Yanyan; Wang, Debao; Liu, Kang; Wang, Lei

2016-07-01

Seven novel multicomponent crystals involving various substituted organic amine molecules and 6-hydroxy-2-naphthoic acid were prepared and characterized by using single crystal X-ray diffraction, infrared and thermogravimetric analyses (TGA). Crystal structures with 1,4-bis(imidazol) butane (L1) 1, 1,4-bis(imidazol-1-ylmethyl)benzene (L2) 2, 1-phenyl piperazine 3, 2-amino-4-hydroxy-6-methyl pyrimidine 4, 4,4'-bipyridine 5, 5,5'-dimethyl-2,2'-dipyridine 6, 2-amino-4,6-dimethyl pyrimidine 7 were determined. Among the seven molecular complexes, total proton transfer from 6-hydroxy-2-naphthoic acid to coformer has occurred in crystals 1-4, while the remaining were cocrystals. X-ray single-crystal structures of these complexes reveal that strong hydrogen bonding O-H···O/N-H···O/O-H···N and weak C-H···O/C-H···π/π···π intermolecular interactions direct the packing modes of molecular crystals together. The analysis of supramolecular synthons in the present structures shows that some classical supramolecular synthons like pyridine-carboxylic acid heterosynthon R22 (7) and aminopyridine-carboxylic acid heterosynthon R22 (8), are again observed in constructing the hydrogen-bonding networks in this paper. Besides, we noticed that water molecules act as a significant hydrogen-bonding connector in constructing supramolecular architectures of 3, 4, 6, and 7.

Thermal conductivity of tungsten: Effects of plasma-related structural defects from molecular-dynamics simulations

NASA Astrophysics Data System (ADS)

Hu, Lin; Wirth, Brian D.; Maroudas, Dimitrios

2017-08-01

We report results on the lattice thermal conductivities of tungsten single crystals containing nanoscale-sized pores or voids and helium (He) nanobubbles as a function of void/bubble size and gas pressure in the He bubbles based on molecular-dynamics simulations. For reference, we calculated lattice thermal conductivities of perfect tungsten single crystals along different crystallographic directions at room temperature and found them to be about 10% of the overall thermal conductivity of tungsten with a weak dependence on the heat flux direction. The presence of nanoscale voids in the crystal causes a significant reduction in its lattice thermal conductivity, which decreases with increasing void size. Filling the voids with He to form He nanobubbles and increasing the bubble pressure leads to further significant reduction of the tungsten lattice thermal conductivity, down to ˜20% of that of the perfect crystal. The anisotropy in heat conduction remains weak for tungsten single crystals containing nanoscale-sized voids and He nanobubbles throughout the pressure range examined. Analysis of the pressure and atomic displacement fields in the crystalline region that surrounds the He nanobubbles reveals that the significant reduction of tungsten lattice thermal conductivity in this region is due to phonon scattering from the nanobubbles, as well as lattice deformation around the nanobubbles and formation of lattice imperfections at higher bubble pressure.

2-(Naphthalen-1-yl)-4-(naphthalen-1-yl­methyl­idene)-1,3-oxazol-5(4H)-one

PubMed Central

Gündoğdu, Cevher; Alp, Serap; Ergün, Yavuz; Tercan, Barış; Hökelek, Tuncer

2011-01-01

In the title compound, C24H15NO2, the oxazole ring is oriented at dihedral angles of 10.09 (4) and 6.04 (4)° with respect to the mean planes of the naphthalene ring systems, while the two naphthalene ring systems make a dihedral angle of 4.32 (3)°. Intra­molecular C—H⋯N hydrogen bonds link the oxazole N atom to the naphthalene ring systems. In the crystal, inter­molecular weak C—H⋯O hydrogen bonds link the mol­ecules into centrosymmetric dimers. π–π contacts between the oxazole and naphthalene rings and between the naphthalene ring systems [centroid–centroid distances = 3.5947 (9) and 3.7981 (9) Å] may further stabilize the crystal structure. Three weak C—H⋯π inter­actions also occur. PMID:21754548

Inkjet Printing Based Mono-layered Photonic Crystal Patterning for Anti-counterfeiting Structural Colors

PubMed Central

Nam, Hyunmoon; Song, Kyungjun; Ha, Dogyeong; Kim, Taesung

2016-01-01

Photonic crystal structures can be created to manipulate electromagnetic waves so that many studies have focused on designing photonic band-gaps for various applications including sensors, LEDs, lasers, and optical fibers. Here, we show that mono-layered, self-assembled photonic crystals (SAPCs) fabricated by using an inkjet printer exhibit extremely weak structural colors and multiple colorful holograms so that they can be utilized in anti-counterfeit measures. We demonstrate that SAPC patterns on a white background are covert under daylight, such that pattern detection can be avoided, but they become overt in a simple manner under strong illumination with smartphone flash light and/or on a black background, showing remarkable potential for anti-counterfeit techniques. Besides, we demonstrate that SAPCs yield different RGB histograms that depend on viewing angles and pattern densities, thus enhancing their cryptographic capabilities. Hence, the structural colorations designed by inkjet printers would not only produce optical holograms for the simple authentication of many items and products but also enable a high-secure anti-counterfeit technique. PMID:27487978

Can Csbnd H⋯Fsbnd C hydrogen bonds alter crystal packing features in the presence of Nsbnd H⋯Odbnd C hydrogen bond?

NASA Astrophysics Data System (ADS)

Yadav, Hare Ram; Choudhury, Angshuman Roy

2017-12-01

Intermolecular interactions involving organic fluorine have been the contemporary field of research in the area of organic solid state chemistry. While a group of researchers had refuted the importance of "organic fluorine" in guiding crystal structures, others have provided evidences for in favor of fluorine mediated interactions in the solid state. Many systematic studies have indicated that the "organic fluorine" is capable of offering weak hydrogen bonds through various supramolecular synthons, mostly in the absence of other stronger hydrogen bonds. Analysis of fluorine mediated interaction in the presence of strong hydrogen bonds has not been highlighted in detail. Hence a thorough structural investigation is needed to understand the role of "organic fluorine" in crystal engineering of small organic fluorinated molecules having the possibility of strong hydrogen bond formation in the solution and in the solid state. To fulfil this aim, we have synthesized a series of fluorinated amides using 3-methoxyphenylacetic acid and fluorinated anilines and studied their structural properties through single crystal and powder X-ray diffraction methods. Our results indicated that the "organic fluorine" plays a significant role in altering the packing characteristics of the molecule in building specific crystal lattices even in the presence of strong hydrogen bond.

Controlling Chirality of Entropic Crystals

NASA Astrophysics Data System (ADS)

Damasceno, Pablo; Karas, Andrew; Schultz, Benjamin; Engel, Michael; Glotzer, Sharon

Colloidal crystal structures with complexity and diversity rivaling atomic and molecular crystals have been predicted and obtained for hard particles by entropy maximization. However, thus far homochiral colloidal crystals, which are candidates for photonic metamaterials, are absent. Using Monte Carlo simulations we show that chiral polyhedra exhibiting weak directional entropic forces self-assemble either an achiral crystal or a chiral crystal with limited control over the crystal handedness. Building blocks with stronger faceting exhibit higher selectivity and assemble a chiral crystal with handedness uniquely determined by the particle chirality. Tuning the strength of directional entropic forces by means of particle rounding or the use of depletants allows for reconfiguration between achiral and homochiral crystals. We rationalize our findings by quantifying the chirality strength of each particle, both from particle geometry and potential of mean force and torque diagrams. Work supported by the National Science Foundation, Division of Materials Research Award No. DMR 1120923, U.S. Army Research Office under Grant Award No. W911NF-10-1-0518, and also by the DOD/ASD (R&E) under Award No. N00244-09-1-0062.

Structure elucidation of 3-[1-(6-methoxy-2-naphtyl)ethyl]-6-(2,4-dichlorophenyl)-7H-1,2,4-triazolo[3,4-b]-1,3,4-thiadiazine, C 23H 18Cl 2N 4OS from synchrotron X-ray powder diffraction

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gündoğdu, Gülsüm; Aytaç, Sevim Peri; Müller, Melanie

The 3-[1-(6-methoxy-2-naphtyl)ethyl]-6-(2,4-dichlorophenyl)-7H-1,2,4-triazolo[3,4-b]-1,3,4-thiadiazine, C 23H 18Cl 2N 4OS compound was synthesized, as a member of the family of novel potential anticancer agents. The structure of the title compound was characterized by IR, 1H-NMR, mass spectroscopy, and elemental analysis, previously. In this study, the crystal structure of this compound has been determined from synchrotron X-ray powder diffraction data. The crystal structure was solved by simulated annealing and the final structure was achieved by Rietveld refinement method using soft restrains on all interatomic bond lengths and angles. This compound crystallizes in space groupP21,Z= 2, with the unit-cell parametersa= 15.55645(11) Å,b= 8.61693(6) Å,c= 8.56702(6)more » Å,β= 104.3270(4)°, andV= 1112.68(1) Å 3. In the crystal structure, strong C-H∙∙∙πand weak intermolecular hydrogen-bonding interactions link the molecules into a three-dimensional network. The molecules are in a head-to-head arrangement in the unit cell.« less

Structural characterization of framework–gas interactions in the metal–organic framework Co2(dobdc) by in situ single-crystal X-ray diffraction† †Electronic supplementary information (ESI) available: Supplementary figures, crystallographic information, adsorption isotherms and fits, CCDC 1530119–1530126. For ESI and crystallographic data in CIF or other electronic format. See DOI: 10.1039/c7sc00449d Click here for additional data file. Click here for additional data file.

PubMed Central

Gonzalez, Miguel I.; Mason, Jarad A.; Bloch, Eric D.; Teat, Simon J.; Gagnon, Kevin J.; Morrison, Gregory Y.; Queen, Wendy L.

2017-01-01

The crystallographic characterization of framework–guest interactions in metal–organic frameworks allows the location of guest binding sites and provides meaningful information on the nature of these interactions, enabling the correlation of structure with adsorption behavior. Here, techniques developed for in situ single-crystal X-ray diffraction experiments on porous crystals have enabled the direct observation of CO, CH4, N2, O2, Ar, and P4 adsorption in Co2(dobdc) (dobdc4– = 2,5-dioxido-1,4-benzenedicarboxylate), a metal–organic framework bearing coordinatively unsaturated cobalt(ii) sites. All these molecules exhibit such weak interactions with the high-spin cobalt(ii) sites in the framework that no analogous molecular structures exist, demonstrating the utility of metal–organic frameworks as crystalline matrices for the isolation and structural determination of unstable species. Notably, the Co–CH4 and Co–Ar interactions observed in Co2(dobdc) represent, to the best of our knowledge, the first single-crystal structure determination of a metal–CH4 interaction and the first crystallographically characterized metal–Ar interaction. Analysis of low-pressure gas adsorption isotherms confirms that these gases exhibit mainly physisorptive interactions with the cobalt(ii) sites in Co2(dobdc), with differential enthalpies of adsorption as weak as –17(1) kJ mol–1 (for Ar). Moreover, the structures of Co2(dobdc)·3.8N2, Co2(dobdc)·5.9O2, and Co2(dobdc)·2.0Ar reveal the location of secondary (N2, O2, and Ar) and tertiary (O2) binding sites in Co2(dobdc), while high-pressure CO2, CO, CH4, N2, and Ar adsorption isotherms show that these binding sites become more relevant at elevated pressures. PMID:28966783

Brownmillerite Ca 2 Co 2 O 5 : Synthesis, Stability, and Re-entrant Single Crystal to Single Crystal Structural Transitions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, Junjie; Zheng, Hong; Malliakas, Christos D.

2014-11-20

We synthesized Ca 2Co 2O 5 in the brownmillerite form using a high-pressure optical-image floating zone furnace, and single crystals with dimensions up to 1.4×0.8×0.5 mm 3 were obtained. At room temperature, Ca 2Co 2O 5 crystallizes as a fully ordered brownmillerite variant in the orthorhombic space group Pcmb (No. 57) with unit cell parameters a=5.28960(10) Å, b=14.9240(2) Å, and c=10.9547(2) Å. Furthermore, with decreasing temperature, it undergoes re-entrant sequence of first-order structural phase transitions (Pcmb→ P2/c11→ P121/m1→ Pcmb) that is unprecedented among brownmillerites, broadening the family of space groups available to these materials and challenging current approaches for sortingmore » the myriad variants of brownmillerite structures. Magnetic susceptibility data indicate antiferromagnetic ordering in Ca 2Co 2O 5 occurs near 240 K, corroborated by neutron powder diffraction. Below 140 K, Ca 2Co 2O 5 shows a weak ferromagnetic component directed primarily along the b axis, and it also exhibits thermal and magnetic history dependence in magnetization.« less

Structural characterization of oxidized titanium surfaces

NASA Astrophysics Data System (ADS)

Jobin, M.; Taborelli, M.; Descouts, P.

1995-05-01

Oxidized titanium surfaces resulting from various processes have been structurally characterized by means of scanning force microscopy, x-ray photoemission spectroscopy (XPS), x-ray diffraction, and electron energy-loss spectroscopy (EELS) with losses in the 0-100 eV range. It has been found that the surface morphology has a granular structure for electropolished titanium and for titanium evaporated on mica at low substrate temperature (570 K), but changes to flat terraces for the films evaporated at higher temperature (770 K). Angular-dependent XPS has revealed the presence of a Ti2O3 suboxide at the Ti/TiO2 interface for electropolished titanium. Dry oxidation has been performed at 770 and 970 K on both weakly and highly crystallized evaporated titanium films oriented along (0001). In the case of underlying crystallized metallic titanium, the resulting TiO2 films are crystallized with the anatase (004) orientation for oxidation at 770 K and with rutile (200) orientation for oxidation at 970 K. EELS spectra interpreted in terms of the molecular orbitals of a (TiO6)8- cluster show that the local octahedral environment of titanium atoms is preserved on native oxides, even if these oxides are not crystallized.

Robust weak anti-localisation effect in strongly textured nanocrystalline Bi2Se3 samples

NASA Astrophysics Data System (ADS)

Pereira, V. M. M.; Henriques, M. S. C.; Paixão, J. A.

2018-05-01

Topological insulators are a quantum state of matter that has recently created a great interest among the scientific community, with Bi2Se3 being one of the most extensively studied materials. Here, we demonstrate that polycrystalline nanostructured samples of Bi2Se3 preserve the existence of topological surface states, where electrons cannot be localised. The nanosheet crystals were synthesised by a microwave-assisted method and their structure, composition and morphology thoroughly characterised. The transport properties of a textured polycrystalline sample with strong preferred orientation along the c-axis were measured, showing the presence of the weak anti-localisation effect and Shubnikov-de Haas oscillations. These features are robust against the presence of non-magnetic impurities and structural defects.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Abdelbaky, Mohammed S.M.; Amghouz, Zakariae; Department of Materials Science and Metallurgical Engineering, University of Oviedo, Campus Universitario, 33203 Gijón

Novel metal phosphonate [CuLi(PPA)] [H{sub 3}PPA=3-phosphonopropionic acid] was synthesized hydrothermally and characterized by single-crystal X-ray diffraction, powder X-ray diffraction, scanning electron microscopy, infrared spectroscopy, and thermogravimetric analysis. It crystallizes in the space group C2/c, with cell parameters a=21.617(2) Å, b=4.9269(2) Å, c=14.342(1) Å, β=132.3(2)°, and Z=8. Its framework is built up from a main trimer, acting as a secondary building unit (SBU), which is formed by vertex-shared between two (LiO{sub 4}) and one (Cu(1)O{sub 4}) polyhedra. These units repeat along b-axis forming infinite inorganic chains, these chains are in turn cross-linked by corner sharing with (Cu(2)O{sub 4}) polyhedra to producemore » inorganic layers lying in the bc-plane. The neighboring layers are connected through the PPA ligand, leading to a 3D pillared-layered structure. The topological analysis reveals that the compound exhibits 3,4,10-c net. Finally, magnetic susceptibility measurement of this compound over the temperature range of 2–300 K reveals the occurrence of weak antiferromagnetic intrachain interactions. - Graphical abstract: Hydrothermal synthesis and structural characterization of a novel lithium-copper phosphonate, formulated as [CuLi(PPA)] (H{sub 3}PPA=3-phosphonopropionic acid), have been reported. This compound has a 3D pillared-layered structure with 3,4,10-c net topology. The magnetic susceptibility data over the temperature range of 2–300 K reveals the occurrence of weak antiferromagnetic interactions. - Highlights: • Novel metal phosphonate, [CuLi(PPA)] (1), has been synthesized and characterized. • Compound 1 has a 3D pillared-layered structure with 3,4,10-c net topology. • Magnetic susceptibility data reveals the occurrence of weak antiferromagnetic interactions.« less

Structural and magnetic characterization of the one-dimensional S = 5/2 antiferromagnetic chain system SrMn(VO 4)(OH)

DOE PAGES

Sanjeewa, Liurukara D.; Garlea, Vasile O.; McGuire, Michael A.; ...

2016-06-06

The descloizite-type compound, SrMn(VO 4)(OH), was synthesized as large single crystals (1-2mm) using a high-temperature high-pressure hydrothermal technique. X-ray single crystal structure analysis reveals that the material crystallizes in the acentric orthorhombic space group of P2 12 12 1 (no. 19), Z = 4. The structure exhibits a one-dimensional feature, with [MnO 4] chains propagating along the a-axis which are interconnected by VO 4 tetrahedra. Raman and infrared spectra were obtained to identify the fundamental vanadate and hydroxide vibrational modes. Magnetization data reveal a broad maximum at approximately 80 K, arising from one-dimensional magnetic correlations with intrachain exchange constant ofmore » J/k B = 9.97(3) K between nearest Mn neighbors and a canted antiferromagnetic behavior below T N = 30 K. Single crystal neutron diffraction at 4 K yielded a magnetic structure solution in the lower symmetry of the magnetic space group P2 1 with two unique chains displaying antiferromagnetically ordered Mn moments oriented nearly perpendicular to the chain axis. Lastly, the presence of the Dzyaloshinskii Moriya antisymmetric exchange interaction leads to a slight canting of the spins and gives rise to a weak ferromagnetic component along the chain direction.« less

2'-Chloro-4-meth-oxy-3-nitro-benzil.

PubMed

Nithya, G; Thanuja, B; Chakkaravarthi, G; Kanagam, Charles C

2011-06-01

In the title compound, C(15)H(10)ClNO(5), the dihedral angle between the aromatic rings is 87.99 (5)°. The O-C-C-O torsion angle between the two carbonyl units is -119.03 (16)°. The crystal structure is stabilized by a weak intermolecular C-H⋯O hydrogen bond.

Crystal structure of 1-(3-chloro-phen-yl)piperazin-1-ium picrate-picric acid (2/1).

PubMed

Kavitha, Channappa N; Jasinski, Jerry P; Kaur, Manpreet; Anderson, Brian J; Yathirajan, H S

2014-11-01

The title salt {systematic name: bis-[1-(3-chloro-phen-yl)piperazinium 2,4,6-tri-nitro-phenolate]-picric acid (2/1)}, 2C10H14ClN2 (+)·2C6H5N3O7 (-)·C6H6N3O7, crystallized with two independent 1-(3-chloro-phen-yl)piperazinium cations, two picrate anions and a picric acid mol-ecule in the asymmetric unit. The six-membered piperazine ring in each cation adopts a slightly distorted chair conformation and contains a protonated N atom. In the picric acid mol-ecule, the mean planes of the nitro groups in the ortho-, meta-, and para-positions are twisted from the benzene ring by 31.5 (3), 7.7 (1), and 3.8 (2)°, respectively. In the anions, the dihedral angles between the benzene ring and the ortho-, meta-, and para-nitro groups are 36.7 (1), 5.0 (6), 4.8 (2)°, and 34.4 (9), 15.3 (8), 4.5 (1)°, respectively. The nitro group in one anion is disordered and was modeled with two sites for one O atom with an occupancy ratio of 0.627 (7):0.373 (7). In the crystal, the picric acid mol-ecule inter-acts with the picrate anion through a trifurcated O-H⋯O four-centre hydrogen bond involving an intra-molecular O-H⋯O hydrogen bond and a weak C-H⋯O inter-action. Weak inter-molecular C-H⋯O inter-actions are responsible for the formation of cation-anion-cation trimers resulting in a chain along [010]. In addition, weak C-H⋯Cl and weak π-π inter-actions [centroid-centroid distances of 3.532 (3), 3.756 (4) and 3.705 (3) Å] are observed and contribute to the stability of the crystal packing.

Nontypical iodine–halogen bonds in the crystal structure of (3 E )-8-chloro-3-iodomethylidene-2,3-dihydro-1,4-oxazino[2,3,4- ij ]quinolin-4-ium triiodide

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bartashevich, E. V.; Batalov, V. I.; Yushina, I. D.

2016-04-29

Two kinds of iodine–iodine halogen bonds are the focus of our attention in the crystal structure of the title salt, C 12H 8ClINO +·I 3 -, described by X-ray diffraction. The first kind is a halogen bond, reinforced by charges, between the I atom of the heterocyclic cation and the triiodide anion. The second kind is the rare case of a halogen bond between the terminal atoms of neighbouring triiodide anions. Lastly, the influence of relatively weakly bound iodine inside an asymmetric triiodide anion on the thermal and Raman spectroscopic properties has been demonstrated.

Crystal structure of 1,3-bis­{[4-(acetyl­sulfanyl)phenyl]ethynyl}azulene

PubMed Central

Förster, Sebastian; Seichter, Wilhelm; Weber, Edwin

2015-01-01

In the title compound, C30H20O2S2, the dihedral angles between the central azulene ring system (r.m.s. deviation = 0.039 Å) and the pendant benzene rings are 28.96 (7) and 55.15 (7)°. The dihedral angles between the benzene rings and their attached acetyl­sulfanyl groups are 59.60 (10) and 84.79 (10)°. The expected π–π stacking inter­actions are not observed in the crystal structure; instead, the packing features C—H⋯O hydrogen bonds, which link the mol­ecules into C(12) [010] chains, which are supported by weak C—H⋯π contacts. PMID:26870518

Raman study of TiO2 role in SiO2-Al2O3-MgO-TiO2-ZnO glass crystallization.

PubMed

Furić, Kresimir; Stoch, Leszek; Dutkiewicz, Jan

2005-05-01

Tough glass-ceramic material of special mechanical properties with nanosize crystal phases formed by appropriately controlled crystallization was studied by Raman spectroscopy. It was obtained by TiO2 activated crystallization of Mg-aluminosilicate glass of SiO2-Al2O3-MgO-TiO2-ZnO composition. Crystallization was preceded by a change in the TiO2 structural position and state, which is manifested by a changed color of glass from yellow into blue shortly before the glass transformation (Tg) temperature. Raman spectroscopy was applied to explain the mechanism of this process and to establish the role of TiO2 in the early stage of glass crystallization that precedes a complete crystal phase formation. The starting glasses were found in almost complete disorder, since all bands were weak, broad and dominated by a Bose band at about 90 cm-1. After the sample annealing all bands turned out better resolved and the Bose band practically disappeared, both confirming the amorphous structure reorganization process. A multiplet observed in the vicinity of 150 cm-1 we assigned to the anatase and other titania structures that can be considered prime centers of crystallization. Finally, in the closest neighborhood of the Rayleigh line the low frequency mode characterizing nanoparticles was observed. According to this band theory, the mean size of initial titania crystallites is about 10nm for all samples, but the size distribution varies within factor two among them.

Raman study of TiO 2 role in SiO 2-Al 2O 3-MgO-TiO 2-ZnO glass crystallization

NASA Astrophysics Data System (ADS)

Furić, Krešimir; Stoch, Leszek; Dutkiewicz, Jan

2005-05-01

Tough glass-ceramic material of special mechanical properties with nanosize crystal phases formed by appropriately controlled crystallization was studied by Raman spectroscopy. It was obtained by TiO 2 activated crystallization of Mg-aluminosilicate glass of SiO 2-Al 2O 3-MgO-TiO 2-ZnO composition. Crystallization was preceded by a change in the TiO 2 structural position and state, which is manifested by a changed color of glass from yellow into blue shortly before the glass transformation ( Tg) temperature. Raman spectroscopy was applied to explain the mechanism of this process and to establish the role of TiO 2 in the early stage of glass crystallization that precedes a complete crystal phase formation. The starting glasses were found in almost complete disorder, since all bands were weak, broad and dominated by a Bose band at about 90 cm -1. After the sample annealing all bands turned out better resolved and the Bose band practically disappeared, both confirming the amorphous structure reorganization process. A multiplet observed in the vicinity of 150 cm -1 we assigned to the anatase and other titania structures that can be considered prime centers of crystallization. Finally, in the closest neighborhood of the Rayleigh line the low frequency mode characterizing nanoparticles was observed. According to this band theory, the mean size of initial titania crystallites is about 10 nm for all samples, but the size distribution varies within factor two among them.

Multi-temperature study of potassium uridine-5'-monophosphate: electron density distribution and anharmonic motion modelling.

PubMed

Jarzembska, Katarzyna N; Řlepokura, Katarzyna; Kamiński, Radosław; Gutmann, Matthias J; Dominiak, Paulina M; Woźniak, Krzysztof

2017-08-01

Uridine, a nucleoside formed of a uracil fragment attached to a ribose ring via a β-N1-glycosidic bond, is one of the four basic components of ribonucleic acid. Here a new anhydrous structure and experimental charge density distribution analysis of a uridine-5'-monophosphate potassium salt, K(UMPH), is reported. The studied case constitutes the very first structure of a 5'-nucleotide potassium salt according to the Cambridge Structural Database. The excellent crystal quality allowed the collection of charge density data at various temperatures, i.e. 10, 100, 200 and 300 K on one single crystal. Crystal structure and charge density data were analysed thoroughly in the context of related literature-reported examples. Detailed analysis of the charge density distribution revealed elevated anharmonic motion of part of the uracil ring moiety relatively weakly interacting with the neighbouring species. The effect was manifested by alternate positive and negative residual density patterns observed for these atoms, which `disappear' at low temperature. It also occurred that the potassium cation, quite uniformly coordinated by seven O atoms from all molecular fragments of the UMPH - anion, including the O atom from the ribofuranose ring, can be treated as spherical in the charge density model which was supported by theoretical calculations. Apart from the predominant electrostatic interactions, four relatively strong hydrogen bond types further support the stability of the crystal structure. This results in a compact and quite uniform structure (in all directions) of the studied crystal, as opposed to similar cases with layered architecture reported in the literature.

Thermolysis synthesis of pure phase NiO from novel sonochemical synthesized Ni(II) nano metal-organic supramolecular architecture.

PubMed

Hanifehpour, Younes; Morsali, Ali; Mirtamizdoust, Babak; Joo, Sang Woo; Soltani, Behzad

2017-07-01

Nano-structures of a new supramolecular coordination compound of divalent nickel with the pyrazol (pzH) containing the terminal azide anions, [Ni(pzH) 2 (N 3 ) 2 ] (1), with discrete molecular architecture (DMA) in solid state was synthesized via sonochemical method. The new nanostructure was characterized by scanning electron microscopy, X-ray powder diffraction, IR, and elemental analysis. Compound 1 was structurally characterized by single crystal X-ray diffraction and the single-crystal X-ray data shows that the coordination number of Ni (II) ions is six, (NiN 6 ), with four N-donor atoms from neutral "pzH" ligands and two N-donors from two terminal azide anions. The supramolecular features in these complexes are guided and controlled by weak directional intermolecular interactions. The structure of the title complex was optimized by density functional theory calculations. Calculated structural parameters and IR spectra for the title complex are consistent with the crystal structure. The NiO nanoparticles were obtained by thermolysis of 1 at 180°C with oleic acid as a surfactant. Copyright © 2017 Elsevier B.V. All rights reserved.

Diethyl [(4-bromo­phen­yl)(5-chloro-2-hydroxy­anilino)meth­yl]phospho­nate

PubMed Central

Babu, V. H. H. Surendra; Krishnaiah, M.; Prasad, G. Syam; C. Suresh Reddy; Kant, Rajni

2009-01-01

In the title compound, C17H20BrClNO4P, inter­molecular C—H⋯O and N—H⋯O hydrogen bonds form centrosymmetric R 2 2(10) dimers linked through O—H⋯O inter­molecular hydrogen bonds, which form centrosymmetric R 2 2(16) dimers. All these hydrogen bonds form chains along [010]. In addition, the crystal structure is stabilized by weak C—H⋯Br hydrogen bonds. The very weak intramolecular N—H⋯O interaction forms a five-membered ring. PMID:21578446

Microstructure and micromechanical elastic properties of weak layers

NASA Astrophysics Data System (ADS)

Köchle, Berna; Matzl, Margret; Proksch, Martin; Schneebeli, Martin

2014-05-01

Weak layers are the mechanically most important stratigraphic layer for avalanches. Yet, there is little known about their exact geometry and their micromechanical properties. To distinguish weak layers or interfaces is essential to assess stability. However, except by destructive mechanical tests, they cannot be easily identified and characterized in the field. We casted natural weak layers and their adjacent layers in the field during two winter seasons and scanned them non-destructively with X-ray computer tomography with a resolution between 10 - 20 µm. Reconstructed three-dimensional models of centimeter-sized layered samples allow for calculating the change of structural properties. We found that structural transitions cannot always by expressed by geometry like density or grain size. In addition, we calculated the Young's modulus and Poisson's ratio of the individual layers with voxel-based finite element simulations. As any material has its characteristic elastic parameters, they may potentially differentiate individual layers, and therefore different microstructures. Our results show that Young's modulus correlates well with density but do not indicate snow's microstructure, in contrast to Poisson's ratio which tends to be lower for strongly anisotropic forms like cup crystals and facets.

Structure, Hydrodynamics, and Phase Transition of Freely Suspended Liquid Crystals

NASA Technical Reports Server (NTRS)

Clark, Noel A.

2000-01-01

Smectic liquid crystals are phases of rod shaped molecules organized into one dimensionally (1D) periodic arrays of layers, each layer being between one and two molecular lengths thick. In the least ordered smectic phases, the smectics A and C, each layer is a two dimensional (2D) liquid. Additionally there are a variety of more ordered smectic phases having hexatic short range translational order or 2D crystalline quasi long range translational order within the layers. The inherent fluid-layer structure and low vapor pressure of smectic liquid crystals enable the long term stabilization of freely suspended, single component, layered fluid films as thin as 30A, a single molecular layer. The layering forces the films to be an integral number of smectic layers thick, quantizing their thickness in layer units and forcing a film of a particular number of layers to be physically homogeneous with respect to its layer structure over its entire area. Optical reflectivity enables the precise determination of the number of layers. These ultrathin freely suspended liquid crystal films are structures of fundamental interest in condensed matter and fluid physics. They are the thinnest known stable condensed phase fluid structures and have the largest surface-to-volume ratio of any stable fluid preparation, making them ideal for the study of the effects of reduced dimensionality on phase behavior and on fluctuation and interface phenomena. Their low vapor pressure and quantized thickness enable the effective use of microgravity to extend the study of basic capillary phenomena to ultrathin fluid films. Freely suspended films have been a wellspring of new liquid crystal physics. They have been used to provide unique experimental conditions for the study of condensed phase transitions in two dimensions. They are the only system in which the hexatic has been unambiguously identified as a phase of matter, and the only physical system in which fluctuations of a 2D XY system and Kosterlitz Thouless phase transition has been observed and 2D XY quasi long range order verified. Smectic films have enabled the precise determination of smectic layer electron density and positional fluctuation profile and have been used to show that the interlayer interactions in anti-ferroelectric tilted smectics do not extend significantly beyond nearest neighbors. The interactions which are operative in liquid crystals are generally weak in comparison to those in crystalline phases, leading to the facile manipulation of the order in liquid crystals by external agents such as applied fields and surfaces. Effects arising from weak ordering are significantly enhanced in ultrathin free films and filaments wherein the intermolecular coupling is effectively reduced by loss of neighbors. Over the past four years this research, which we now detail, has produced a host of exciting new discoveries and unexpected results, maintaining the position of the study of freely suspended liquid crystal structures as one of most exciting and fruitful areas of complex fluid physics. In addition, several potentially interesting microgravity free film experiments have been identified.

Soliton self-frequency shift controlled by a weak seed laser in tellurite photonic crystal fibers.

PubMed

Liu, Lai; Meng, Xiangwei; Yin, Feixiang; Liao, Meisong; Zhao, Dan; Qin, Guanshi; Ohishi, Yasutake; Qin, Weiping

2013-08-01

We report the first demonstration of soliton self-frequency shift (SSFS) controlled by a weak continuous-wave (CW) laser, from a tellurite photonic crystal fiber pumped by a 1560 nm femtosecond fiber laser. The control of SSFS is performed by the cross-gain modulation of the 1560 nm femtosecond laser. By varying the input power of the weak CW laser (1560 nm) from 0 to 1.17 mW, the soliton generated in the tellurite photonic crystal fiber blue shifts from 1935 to 1591 nm. The dependence of the soliton wavelength on the operation wavelength of the weak CW laser is also measured. The results show the CW laser with a wavelength tunable range of 1530-1592 nm can be used to control the SSFS generation.

Crystal structure of Helicobacter pylori neutrophil-activating protein with a di-nuclear ferroxidase center in a zinc or cadmium-bound form

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yokoyama, Hideshi, E-mail: h-yokoya@u-shizuoka-ken.ac.jp; Tsuruta, Osamu; Akao, Naoya

2012-06-15

Highlights: Black-Right-Pointing-Pointer Structures of a metal-bound Helicobacter pylori neutrophil-activating protein were determined. Black-Right-Pointing-Pointer Two zinc ions were tetrahedrally coordinated by ferroxidase center (FOC) residues. Black-Right-Pointing-Pointer Two cadmium ions were coordinated in a trigonal-bipyramidal and octahedral manner. Black-Right-Pointing-Pointer The second metal ion was more weakly coordinated than the first at the FOC. Black-Right-Pointing-Pointer A zinc ion was found in one negatively-charged pore suitable as an ion path. -- Abstract: Helicobacter pylori neutrophil-activating protein (HP-NAP) is a Dps-like iron storage protein forming a dodecameric shell, and promotes adhesion of neutrophils to endothelial cells. The crystal structure of HP-NAP in a Zn{sup 2+}-more » or Cd{sup 2+}-bound form reveals the binding of two zinc or two cadmium ions and their bridged water molecule at the ferroxidase center (FOC). The two zinc ions are coordinated in a tetrahedral manner to the conserved residues among HP-NAP and Dps proteins. The two cadmium ions are coordinated in a trigonal-bipyramidal and distorted octahedral manner. In both structures, the second ion is more weakly coordinated than the first. Another zinc ion is found inside of the negatively-charged threefold-related pore, which is suitable for metal ions to pass through.« less

Glassy phases and driven response of the phase-field-crystal model with random pinning.

PubMed

Granato, E; Ramos, J A P; Achim, C V; Lehikoinen, J; Ying, S C; Ala-Nissila, T; Elder, K R

2011-09-01

We study the structural correlations and the nonlinear response to a driving force of a two-dimensional phase-field-crystal model with random pinning. The model provides an effective continuous description of lattice systems in the presence of disordered external pinning centers, allowing for both elastic and plastic deformations. We find that the phase-field crystal with disorder assumes an amorphous glassy ground state, with only short-ranged positional and orientational correlations, even in the limit of weak disorder. Under increasing driving force, the pinned amorphous-glass phase evolves into a moving plastic-flow phase and then, finally, a moving smectic phase. The transverse response of the moving smectic phase shows a vanishing transverse critical force for increasing system sizes.

Data Mining for New Two- and One-Dimensional Weakly Bonded Solids and Lattice-Commensurate Heterostructures.

PubMed

Cheon, Gowoon; Duerloo, Karel-Alexander N; Sendek, Austin D; Porter, Chase; Chen, Yuan; Reed, Evan J

2017-03-08

Layered materials held together by weak interactions including van der Waals forces, such as graphite, have attracted interest for both technological applications and fundamental physics in their layered form and as an isolated single-layer. Only a few dozen single-layer van der Waals solids have been subject to considerable research focus, although there are likely to be many more that could have superior properties. To identify a broad spectrum of layered materials, we present a novel data mining algorithm that determines the dimensionality of weakly bonded subcomponents based on the atomic positions of bulk, three-dimensional crystal structures. By applying this algorithm to the Materials Project database of over 50,000 inorganic crystals, we identify 1173 two-dimensional layered materials and 487 materials that consist of weakly bonded one-dimensional molecular chains. This is an order of magnitude increase in the number of identified materials with most materials not known as two- or one-dimensional materials. Moreover, we discover 98 weakly bonded heterostructures of two-dimensional and one-dimensional subcomponents that are found within bulk materials, opening new possibilities for much-studied assembly of van der Waals heterostructures. Chemical families of materials, band gaps, and point groups for the materials identified in this work are presented. Point group and piezoelectricity in layered materials are also evaluated in single-layer forms. Three hundred and twenty-five of these materials are expected to have piezoelectric monolayers with a variety of forms of the piezoelectric tensor. This work significantly extends the scope of potential low-dimensional weakly bonded solids to be investigated.

Crystal structure across the β to α phase transition in thermoelectric Cu 2–xSe

DOE Office of Scientific and Technical Information (OSTI.GOV)

Eikeland, Espen; Blichfeld, Anders B.; Borup, Kasper A.

Here, the crystal structure uniquely imparts the specific properties of a material, and thus provides the starting point for any quantitative understanding of thermoelectric properties. Cu 2–xSe is an intensely studied high performing, non-toxic and cheap thermoelectric material, and here for the first time, the average structure of β-Cu 2–xSe is reported based on analysis of multi-temperature single-crystal X-ray diffraction data. It consists of Se–Cu layers with additional copper between every alternate layer. The structural changes during the peculiar zT enhancing phase transition mainly consist of changes in the inter-layer distance coupled with subtle Cu migration. Just prior to themore » transition the structure exhibits strong negative thermal expansion due to the reordering of Cu atoms, when approached from low temperatures. The phase transition is fully reversible and group–subgroup symmetry relations are derived that relate the low-temperature β-phase to the high-temperature α-phase. Weak superstructure reflections are observed and a possible Cu ordering is proposed. The structural rearrangement may have a significant impact on the band structure and the Cu rearrangement may also be linked to an entropy increase. Both factors potentially contribute to the extraordinary zT enhancement across the phase transition.« less

Crystal structure across the β to α phase transition in thermoelectric Cu 2–xSe

DOE PAGES

Eikeland, Espen; Blichfeld, Anders B.; Borup, Kasper A.; ...

2017-06-13

Here, the crystal structure uniquely imparts the specific properties of a material, and thus provides the starting point for any quantitative understanding of thermoelectric properties. Cu 2–xSe is an intensely studied high performing, non-toxic and cheap thermoelectric material, and here for the first time, the average structure of β-Cu 2–xSe is reported based on analysis of multi-temperature single-crystal X-ray diffraction data. It consists of Se–Cu layers with additional copper between every alternate layer. The structural changes during the peculiar zT enhancing phase transition mainly consist of changes in the inter-layer distance coupled with subtle Cu migration. Just prior to themore » transition the structure exhibits strong negative thermal expansion due to the reordering of Cu atoms, when approached from low temperatures. The phase transition is fully reversible and group–subgroup symmetry relations are derived that relate the low-temperature β-phase to the high-temperature α-phase. Weak superstructure reflections are observed and a possible Cu ordering is proposed. The structural rearrangement may have a significant impact on the band structure and the Cu rearrangement may also be linked to an entropy increase. Both factors potentially contribute to the extraordinary zT enhancement across the phase transition.« less

The stability of a crystal with diamond structure for patchy particles with tetrahedral symmetry.

PubMed

Noya, Eva G; Vega, Carlos; Doye, Jonathan P K; Louis, Ard A

2010-06-21

The phase diagram of model anisotropic particles with four attractive patches in a tetrahedral arrangement has been computed at two different values of the range of the potential, with the aim of investigating the conditions under which a diamond crystal can be formed. We find that the diamond phase is never stable for our longer-ranged potential. At low temperatures and pressures, the fluid freezes into a body-centered-cubic solid that can be viewed as two interpenetrating diamond lattices with a weak interaction between the two sublattices. Upon compression, an orientationally ordered face-centered-cubic crystal becomes more stable than the body-centered-cubic crystal, and at higher temperatures, a plastic face-centered-cubic phase is stabilized by the increased entropy due to orientational disorder. A similar phase diagram is found for the shorter-ranged potential, but at low temperatures and pressures, we also find a region over which the diamond phase is thermodynamically favored over the body-centered-cubic phase. The higher vibrational entropy of the diamond structure with respect to the body-centered-cubic solid explains why it is stable even though the enthalpy of the latter phase is lower. Some preliminary studies on the growth of the diamond structure starting from a crystal seed were performed. Even though the diamond phase is never thermodynamically stable for the longer-ranged model, direct coexistence simulations of the interface between the fluid and the body-centered-cubic crystal and between the fluid and the diamond crystal show that at sufficiently low pressures, it is quite probable that in both cases the solid grows into a diamond crystal, albeit involving some defects. These results highlight the importance of kinetic effects in the formation of diamond crystals in systems of patchy particles.

Investigation and characterization of ZnO single crystal microtubes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Al-Naser, Qusay A.H.; Zhou, Jian, E-mail: jianzhou@whut.edu.cn; Liu, Guizhen

2016-04-15

Morphological, structural, and optical characterization of microwave synthesized ZnO single crystal microtubes were investigated in this work. The structure and morphology of the ZnO microtubes are characterized using X-ray diffraction (XRD), single crystal diffraction (SCD), field emission scanning electron microscopy (FESEM), energy dispersive X-ray spectroscopy (EDX), and transmission electron microscopy (TEM). The results reveal that the as-synthesized ZnO microtube has a highly regular hexagonal cross section and smooth surfaces with an average length of 650–700 μm, an average outer diameter of 50 μm and wall thickness of 1–3 μm, possessing a single crystal wurtzite hexagonal structure. Optical properties of ZnOmore » single crystal microtubes were investigated by photoluminescence (PL) and ultraviolet-visible (UV-vis) absorption techniques. Room-temperature PL spectrum of the microtube reveal a strong UV emission peak at around 375.89 nm and broad and a weak visible emission with a main peak identified at 577 nm, which was assigned to the nearest band-edge emission and the deep-level emission, respectively. The band gap energy of ZnO microtube was found to be 3.27 eV. - Highlights: • ZnO microtube length of 650–700 μm, diameter of 50 μm, wall thickness of 1–3 μm • ZnO microtube possesses a single crystal wurtzite hexagonal structure. • The crystal system is hexahedral oriented along a-axis with indices of (100). • A strong and sharp UV emission at 375.89 nm (3.29 eV) • One prominent absorption band around 378.88 nm (3.27 eV)« less

Synthesis, crystal structure, and electrical and magnetic properties of BaMo{sub 6}Te{sub 6}: A novel reduced molybdenum telluride containing infinite chains of trans-face shared Mo{sub 6} octahedra

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gall, Philippe; Guizouarn, Thierry; Potel, Michel

Powder samples and single crystals of the new ternary compound BaMo{sub 6}Te{sub 6} were obtained by solid state reaction. The structure was determined by single-crystal X-ray diffraction. BaMo{sub 6}Te{sub 6} crystallizes in the hexagonal space group P6{sub 3}/m (No. 176) with unit-cell parameters a=9.3941(2) Å, c=4.5848(1) Å and Z=1. Full-matrix least-squares refinement on F{sup 2} using 452 independent reflections for 17 refinable parameters resulted in R1=0.0208 and wR2=0.0539. The structure consists of one-dimensional infinite chains of trans-face shared Mo{sub 6} octahedra capped by Se atoms. These chains that are running along the c axis are separated from each other bymore » nine-coordinate Ba atoms. Resistivity measurements on a single crystal indicated that the BaMo{sub 6}Te{sub 6} compound is metallic down to 160 K and semiconductor below. Magnetic susceptibility measurements showed that BaMo{sub 6}Te{sub 6} is weakly diamagnetic with no anomaly at the metal–semiconductor transition. - Graphical abstract: We present here the synthesis, the crystal structure, and the electrical and magnetic properties of the new compound BaMo{sub 6}Te{sub 6} containing infinite chains of trans-face shared Mo{sub 6} octahedra. - Highlights: • BaMo{sub 6}Te{sub 6} contains infinite chains of trans-face-sharing Mo{sub 6} octahedra |Mo{sub 6/2}|{sub ∞}{sup 1}. • Synthesis by solid state reaction. • Single-crystal X-ray study. • Continuous metal–nonmetal transition. • Anderson localization.« less

Molecular and crystal structure and the Hirshfeld surface analysis of 1-amino-1-deoxy-α-D-sorbopyranose and 1-amino-1-deoxy-α-D-psicopyranose ("D-sorbosamine" and "D-psicosamine") derivatives

NASA Astrophysics Data System (ADS)

Mossine, Valeri V.; Barnes, Charles L.; Mawhinney, Thomas P.

2018-05-01

Sorbosamine and psicosamine are the last two 1-amino-1-deoxy-hexuloses for which no structural data were available. We report on a13C NMR and a single crystal X-ray diffraction study of 1-deoxy-1-(N-methylphenylamino)-D-sorbose (1) and 1-deoxy-1-(N-methylphenylamino)-D-psicose (2). In solutions, both aminosugars are conformationally unstable and establish equilibria, with 90.7% α-pyranose, 3.8% α-furanose, 1.0% β-pyranose, 0.5% β-furanose, and 4.0% acyclic keto form for 1 and 32.4% α-furanose, 27.2% α-pyranose, 21.0% β-pyranose, 9.1% β-furanose, and 11.0% acyclic keto form for 2. X-ray diffraction data provided detailed structural information on 1 and 2 in the α-pyranose form. Both molecules adopt the 5C2 ring conformations, the bond distances and valence angles compare well with respective pyranose structures. All hydroxyl groups in crystal structures of both 1 and 2 participate in two-dimensional hydrogen bonding networks, the H-bonding pattern in 1 is dominated by co-crystallized water molecules. The Hirshfeld surface analysis revealed a significant contribution of non- or weakly polar interactions to the packing forces for both molecules, with crystal structure of 2 featuring short H⋯H contacts. Other structural features found in 2 are a significant planarity of the tertiary amino group (the pyramid heights are 0.127 Å in 2 vs 0.231 Å in 1), a concomitant non-involvement of the amine nitrogen in heteroatom contacts, and a unique anti-periplanar conformation around the C1sbnd C2 bond.

VO{sub 2} (A): Reinvestigation of crystal structure, phase transition and crystal growth mechanisms

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rao Popuri, Srinivasa; University of Bordeaux, ICMCB, UPR 9048, F-33608 Pessac; National Institute for Research and Development in Electrochemistry and Condensed Matter, Timisoara, Plautius Andronescu Str. No. 1, 300224 Timisoara

2014-05-01

Well crystallized VO{sub 2} (A) microrods were grown via a single step hydrothermal reaction in the presence of V{sub 2}O{sub 5} and oxalic acid. With the advantage of high crystalline samples, we propose P4/ncc as an appropriate space group at room temperature. From morphological studies, we found that the oriented attachment and layer by layer growth mechanisms are responsible for the formation of VO{sub 2} (A) micro rods. The structural and electronic transitions in VO{sub 2} (A) are strongly first order in nature, and a marked difference between the structural transition temperatures and electronic transitions temperature was evidenced. The reversiblemore » intra- (LTP-A to HTP-A) and irreversible inter- (HTP-A to VO{sub 2} (M1)) structural phase transformations were studied by in-situ powder X-ray diffraction. Attempts to increase the size of the VO{sub 2} (A) microrods are presented and the possible formation steps for the flower-like morphologies of VO{sub 2} (M1) are described. - Graphical abstract: Using a single step and template free hydrothermal synthesis, well crystallized VO{sub 2} (A) microrods were prepared and the P4/ncc space group was assigned to the room temperature crystal structure. Reversible and irreversible phase transitions among different VO{sub 2} polymorphs were identified and their progressive nature was highlighted. Attempts to increase the microrods size, involving layer by layer formation mechanisms, are presented. - Highlights: • Highly crystallized VO{sub 2} (A) microrods were grown via a single step hydrothermal process. • The P4/ncc space group was determined for VO{sub 2} (A) at room temperature. • The electronic structure and progressive nature of the structural phase transition were investigated. • A weak coupling between structural and electronic phase transitions was identified. • Different crystallite morphologies were discussed in relation with growth mechanisms.« less

Design of weak link channel-cut crystals for fast QEXAFS monochromators

DOE Office of Scientific and Technical Information (OSTI.GOV)

Polheim, O. von, E-mail: vonpolheim@uni-wuppertal.de; Müller, O.; Lützenkirchen-Hecht, D.

2016-07-27

A weak link channel-cut crystal, optimized for dedicated Quick EXAFS monochromators and measurements, was designed using finite element analysis. This channel-cut crystal offers precise detuning capabilities to enable suppression of higher harmonics in the virtually monochromatic beam. It was optimized to keep the detuning stable, withstanding the mechanical load, which occurs during oscillations with up to 50 Hz. First tests at DELTA (Dortmund, Germany), proved the design.

2′-Chloro-4-meth­oxy-3-nitro­benzil

PubMed Central

Nithya, G.; Thanuja, B.; Chakkaravarthi, G.; Kanagam, Charles C.

2011-01-01

In the title compound, C15H10ClNO5, the dihedral angle between the aromatic rings is 87.99 (5)°. The O—C—C—O torsion angle between the two carbonyl units is −119.03 (16)°. The crystal structure is stabilized by a weak intermolecular C—H⋯O hydrogen bond. PMID:21754895

Photoemission study of the electronic structure and charge density waves of Na2Ti2Sb2O.

PubMed

Tan, S Y; Jiang, J; Ye, Z R; Niu, X H; Song, Y; Zhang, C L; Dai, P C; Xie, B P; Lai, X C; Feng, D L

2015-04-30

The electronic structure of Na2Ti2Sb2O single crystal is studied by photon energy and polarization dependent angle-resolved photoemission spectroscopy (ARPES). The obtained band structure and Fermi surface agree well with the band structure calculation of Na2Ti2Sb2O in the non-magnetic state, which indicates that there is no magnetic order in Na2Ti2Sb2O and the electronic correlation is weak. Polarization dependent ARPES results suggest the multi-band and multi-orbital nature of Na2Ti2Sb2O. Photon energy dependent ARPES results suggest that the electronic structure of Na2Ti2Sb2O is rather two-dimensional. Moreover, we find a density wave energy gap forms below the transition temperature and reaches 65 meV at 7 K, indicating that Na2Ti2Sb2O is likely a weakly correlated CDW material in the strong electron-phonon interaction regime.

H/D isotopic recognition and temperature effects in IR spectra of hydrogen-bonded cyclic dimers in crystals: 3-Methylcinnamic acid and 4-phenylbutyric acid

NASA Astrophysics Data System (ADS)

Hachuła, Barbara; Jabłońska-Czapla, Magdalena; Flakus, Henryk T.; Nowak, Maria; Kusz, Joachim

2015-01-01

In the present work, the experimental and theoretical study of the nature of the inter-hydrogen bond interactions in two different carboxylic acids, 3-methylcinnamic acid (3MCA) and 4-phenylbutyric acid (4PBA), were reported. The polarized IR spectra of 3MCA and 4PBA crystals were recorded at the frequency ranges of the νOsbnd H and νOsbnd D bands. The spectral properties of 3MCA and 4PBA interpreted with the aid of the calculations based on the "strong-coupling" model. The differences in the spectral properties of the two different dimeric systems in the crystals provide a valuable information about the existence of a direct relationship between the crystal spectral properties in IR and the electronic structure of the molecular systems. In 3MCA crystals strong vibrational exciton interactions favor a "tail-to-head" (TH)-type Davydov coupling widespread via the π-electrons, whereas in 4PBA crystals a weak "through-space" (SS) exciton coupling is responsible for a "side-to-side"-type coupling. The relative contribution of each individual exciton coupling mechanism in IR spectra generation strongly depends on temperature and molecular electronic structure. The H/D isotopic recognition effect, depending on a non-random distribution of protons and deuterons in the crystal hydrogen bridges, was also analyzed.

H/D isotopic recognition and temperature effects in IR spectra of hydrogen-bonded cyclic dimers in crystals: 3-methylcinnamic acid and 4-phenylbutyric acid.

PubMed

Hachuła, Barbara; Jabłońska-Czapla, Magdalena; Flakus, Henryk T; Nowak, Maria; Kusz, Joachim

2015-01-05

In the present work, the experimental and theoretical study of the nature of the inter-hydrogen bond interactions in two different carboxylic acids, 3-methylcinnamic acid (3MCA) and 4-phenylbutyric acid (4PBA), were reported. The polarized IR spectra of 3MCA and 4PBA crystals were recorded at the frequency ranges of the νO-H and νO-D bands. The spectral properties of 3MCA and 4PBA interpreted with the aid of the calculations based on the "strong-coupling" model. The differences in the spectral properties of the two different dimeric systems in the crystals provide a valuable information about the existence of a direct relationship between the crystal spectral properties in IR and the electronic structure of the molecular systems. In 3MCA crystals strong vibrational exciton interactions favor a "tail-to-head" (TH)-type Davydov coupling widespread via the π-electrons, whereas in 4PBA crystals a weak "through-space" (SS) exciton coupling is responsible for a "side-to-side"-type coupling. The relative contribution of each individual exciton coupling mechanism in IR spectra generation strongly depends on temperature and molecular electronic structure. The H/D isotopic recognition effect, depending on a non-random distribution of protons and deuterons in the crystal hydrogen bridges, was also analyzed. Copyright © 2014 Elsevier B.V. All rights reserved.

Synchrotron X-ray diffuse scattering from a stable polymorphic material: terephthalic acid, C 8 H 6 O 4

DOE Office of Scientific and Technical Information (OSTI.GOV)

Goossens, D. J.; Chan, E. J.

Terephthalic acid (TPA, C 8H 6O 4) is an industrially important chemical, one that shows polymorphism and disorder. Three polymorphs are known, two triclinic [(I) and (II)] and one monoclinic (III). Of the two triclinic polymorphs, (II) has been shown to be more stable in ambient conditions. This paper presents models of the local order of polymorphs (I) and (II), and compares the single-crystal diffuse scattering (SCDS) computed from the models with that observed from real crystals. TPA shows relatively weak and less-structured diffuse scattering than some other polymorphic materials, but it does appear that the SCDS is less wellmore » modelled by a purely harmonic model in polymorph (I) than in polymorph (II), according to the idea that the diffuse scattering is sensitive to anharmonicity that presages a structural phase transition. The work here verifies that displacive correlations are strong along the molecular chains and weak laterally, and that it is not necessary to allow the —COOH groups to librate to successfully model the diffuse scattering – keeping in mind that the data are from X-ray diffraction and not directly sensitive to H atoms.« less

Wave propagation in a strongly nonlinear locally resonant granular crystal

NASA Astrophysics Data System (ADS)

Vorotnikov, K.; Starosvetsky, Y.; Theocharis, G.; Kevrekidis, P. G.

2018-02-01

In this work, we study the wave propagation in a recently proposed acoustic structure, the locally resonant granular crystal. This structure is composed of a one-dimensional granular crystal of hollow spherical particles in contact, containing linear resonators. The relevant model is presented and examined through a combination of analytical approximations (based on ODE and nonlinear map analysis) and of numerical results. The generic dynamics of the system involves a degradation of the well-known traveling pulse of the standard Hertzian chain of elastic beads. Nevertheless, the present system is richer, in that as the primary pulse decays, secondary ones emerge and eventually interfere with it creating modulated wavetrains. Remarkably, upon suitable choices of parameters, this interference "distills" a weakly nonlocal solitary wave (a "nanopteron"). This motivates the consideration of such nonlinear structures through a separate Fourier space technique, whose results suggest the existence of such entities not only with a single-side tail, but also with periodic tails on both ends. These tails are found to oscillate with the intrinsic oscillation frequency of the out-of-phase motion between the outer hollow bead and its internal linear attachment.

Local order and crystallization of dense polydisperse hard spheres

NASA Astrophysics Data System (ADS)

Coslovich, Daniele; Ozawa, Misaki; Berthier, Ludovic

2018-04-01

Computer simulations give precious insight into the microscopic behavior of supercooled liquids and glasses, but their typical time scales are orders of magnitude shorter than the experimentally relevant ones. We recently closed this gap for a class of models of size polydisperse fluids, which we successfully equilibrate beyond laboratory time scales by means of the swap Monte Carlo algorithm. In this contribution, we study the interplay between compositional and geometric local orders in a model of polydisperse hard spheres equilibrated with this algorithm. Local compositional order has a weak state dependence, while local geometric order associated to icosahedral arrangements grows more markedly but only at very high density. We quantify the correlation lengths and the degree of sphericity associated to icosahedral structures and compare these results to those for the Wahnström Lennard-Jones mixture. Finally, we analyze the structure of very dense samples that partially crystallized following a pattern incompatible with conventional fractionation scenarios. The crystal structure has the symmetry of aluminum diboride and involves a subset of small and large particles with size ratio approximately equal to 0.5.

Crystal structures of Boro-AFm and sBoro-AFt phases

DOE Office of Scientific and Technical Information (OSTI.GOV)

Champenois, Jean-Baptiste; Mesbah, Adel; Clermont Universite, ENSCCF, Institut de Chimie de Clermont-Ferrand, BP 10448, F-63000 Clermont-Ferrand

2012-10-15

Crystal structures of boron-containing AFm (B-AFm) and AFt (B-AFt) phases have been solved ab-initio and refined from X-ray powder diffraction. {sup 11}B NMR and Raman spectroscopies confirm the boron local environment in both compounds: three-fold coordinated in B-AFm corresponding to HBO{sub 3}{sup 2-} species, and four-fold coordinated in B-AFt corresponding to B (OH){sub 4}{sup -} species. B-AFm crystallizes in the rhombohedral R3{sup Macron }c space group and has the 3CaO{center_dot}Al{sub 2}O{sub 3}{center_dot}CaHBO{sub 3}{center_dot}12H{sub 2}O (4CaO{center_dot}Al{sub 2}O{sub 3}{center_dot}1/2B{sub 2}O{sub 3}{center_dot}12.5H{sub 2}O, C{sub 4}AB{sub 1/2}H{sub 12.5}) general formulae with planar trigonal HBO{sub 3}{sup 2-} anions weakly bonded at the centre of themore » interlayer region. One HBO{sub 3}{sup 2-} anion is statistically distributed with two weakly bonded water molecules on the same crystallographic site. B-AFt crystallizes in the trigonal P3cl space group and has the 3CaO{center_dot}Al{sub 2}O{sub 3}{center_dot}Ca(OH){sub 2}{center_dot}2Ca(B (OH){sub 4}){sub 2}{center_dot}24H{sub 2}O (6CaO{center_dot}Al{sub 2}O{sub 3}{center_dot}2B{sub 2}O{sub 3}{center_dot}33H{sub 2}O, C{sub 6}AB{sub 2}H{sub 33}) general formulae with tetrahedral B (OH){sub 4}{sup -} anions located in the channel region of the structure. All tetrahedral anions are oriented in a unique direction, leading to a hexagonal c lattice parameter about half that of ettringite.« less

Roles of bond orientational ordering in glass transition and crystallization.

PubMed

Tanaka, Hajime

2011-07-20

It is widely believed that crystallization in three dimensions is primarily controlled by positional ordering, and not by bond orientational ordering. In other words, bond orientational ordering is usually considered to be merely a consequence of positional ordering and thus has often been ignored. This one-order-parameter (density) description may be reasonable when we consider an equilibrium liquid-solid transition, but may not be enough to describe a metastable state and the kinetics of the transition. Here we propose that bond orientational ordering can play a key role in (i) crystallization, (ii) the ordering to quasi-crystal and (iii) vitrification, which occurs under rather weak frustration against crystallization. In a metastable supercooled state before crystallization, a system generally tends to have bond orientational order at least locally as a result of a constraint of dense packing. For a system interacting with hard-core repulsions, the constraint is intrinsically of geometrical origin and thus the basic physics is the same as nematic ordering of rod-like particles upon densification. Furthermore, positional ordering is easily destroyed even by weak frustration such as polydispersity and anisotropic interactions which favour a symmetry not consistent with that of the equilibrium crystal. Thus we may say that vitrification can be achieved by disturbing and prohibiting long-range positional ordering. Even in such a situation, bond orientational ordering still survives, accompanying its critical-like fluctuations, which are the origin of dynamic heterogeneity for this case. This scenario naturally explains both the absence of positional order and the development of bond orientational order upon cooling in a supercooled state. Although our argument is speculative in nature, we emphasize that this physical picture can coherently explain crystallization, vitrification, quasi-crystallization and their relationship in a natural manner. For a strongly frustrated system, even bond orientational order can be destroyed. Even in such a case there may still appear a structural signature of dense packing, which is linked to slow dynamics.

Reversible and nonvolatile ferroelectric control of two-dimensional electronic transport properties of ZrCuSiAs-type copper oxyselenide thin films with a layered structure

NASA Astrophysics Data System (ADS)

Zhao, Xu-Wen; Gao, Guan-Yin; Yan, Jian-Min; Chen, Lei; Xu, Meng; Zhao, Wei-Yao; Xu, Zhi-Xue; Guo, Lei; Liu, Yu-Kuai; Li, Xiao-Guang; Wang, Yu; Zheng, Ren-Kui

2018-05-01

Copper-based ZrCuSiAs-type compounds of LnCuChO (Ln =Bi and lanthanides, Ch =S , Se, Te) with a layered crystal structure continuously attract worldwide attention in recent years. Although their high-temperature (T ≥ 300 K) electrical properties have been intensively studied, their low-temperature electronic transport properties are little known. In this paper, we report the integration of ZrCuSiAs-type copper oxyselenide thin films of B i0.94P b0.06CuSeO (BPCSO) with perovskite-type ferroelectric Pb (M g1 /3N b2 /3 ) O3-PbTi O3 (PMN-PT) single crystals in the form of ferroelectric field effect devices that allow us to control the electronic properties (e.g., carrier density, magnetoconductance, dephasing length, etc.) of BPCSO films in a reversible and nonvolatile manner by polarization switching at room temperature. Combining ferroelectric gating and magnetotransport measurements with the Hikami-Larkin-Nagaoka theory, we demonstrate two-dimensional (2D) electronic transport characteristics and weak antilocalization effect as well as strong carrier-density-mediated competition between weak antilocalization and weak localization in BPCSO films. Our results show that ferroelectric gating using PMN-PT provides an effective and convenient approach to probe the carrier-density-related 2D electronic transport properties of ZrCuSiAs-type copper oxyselenide thin films.

A crystal structure of the bifunctional antibiotic simocyclinone D8, bound to DNA gyrase.

PubMed

Edwards, Marcus J; Flatman, Ruth H; Mitchenall, Lesley A; Stevenson, Clare E M; Le, Tung B K; Clarke, Thomas A; McKay, Adam R; Fiedler, Hans-Peter; Buttner, Mark J; Lawson, David M; Maxwell, Anthony

2009-12-04

Simocyclinones are bifunctional antibiotics that inhibit bacterial DNA gyrase by preventing DNA binding to the enzyme. We report the crystal structure of the complex formed between the N-terminal domain of the Escherichia coli gyrase A subunit and simocyclinone D8, revealing two binding pockets that separately accommodate the aminocoumarin and polyketide moieties of the antibiotic. These are close to, but distinct from, the quinolone-binding site, consistent with our observations that several mutations in this region confer resistance to both agents. Biochemical studies show that the individual moieties of simocyclinone D8 are comparatively weak inhibitors of gyrase relative to the parent compound, but their combination generates a more potent inhibitor. Our results should facilitate the design of drug molecules that target these unexploited binding pockets.

Rapid liquid phase sintered Mn doped BiFeO3 ceramics with enhanced polarization and weak magnetization

NASA Astrophysics Data System (ADS)

Kumar, Manoj; Yadav, K. L.

2007-12-01

Single-phase BiFe1-xMnxO3 multiferroic ceramics have been synthesized by rapid liquid phase sintering method to study the influence of Mn substitution on their crystal structure, dielectric, magnetic, and ferroelectric behaviors. From XRD analysis it is seen that Mn substitution does not affect the crystal structure of the BiFe1-xMnxO3 system. An enhancement in magnetization was observed for BiFe1-xMnxO3 ceramics. However, the ferooelectric hysteresis loops were not really saturated, we observed a spontaneous polarization of 10.23μC /cm2 under the applied field of 42kV/cm and remanent polarization of 3.99μC/cm2 for x =0.3 ceramic.

Crystal structure and solution species of Ce(III) and Ce(IV) formates: from mononuclear to hexanuclear complexes.

PubMed

Hennig, Christoph; Ikeda-Ohno, Atsushi; Kraus, Werner; Weiss, Stephan; Pattison, Philip; Emerich, Hermann; Abdala, Paula M; Scheinost, Andreas C

2013-10-21

Cerium(III) and cerium(IV) both form formate complexes. However, their species in aqueous solution and the solid-state structures are surprisingly different. The species in aqueous solutions were investigated with Ce K-edge EXAFS spectroscopy. Ce(III) formate shows only mononuclear complexes, which is in agreement with the predicted mononuclear species of Ce(HCOO)(2+) and Ce(HCOO)2(+). In contrast, Ce(IV) formate forms in aqueous solution a stable hexanuclear complex of [Ce6(μ3-O)4(μ3-OH)4(HCOO)x(NO3)y](12-x-y). The structural differences reflect the different influence of hydrolysis, which is weak for Ce(III) and strong for Ce(IV). Hydrolysis of Ce(IV) ions causes initial polymerization while complexation through HCOO(-) results in 12 chelate rings stabilizing the hexanuclear Ce(IV) complex. Crystals were grown from the above-mentioned solutions. Two crystal structures of Ce(IV) formate were determined. Both form a hexanuclear complex with a [Ce6(μ3-O)4(μ3-OH)4](12+) core in aqueous HNO3/HCOOH solution. The pH titration with NaOH resulted in a structure with the composition [Ce6(μ3-O)4(μ3-OH)4(HCOO)10(NO3)2(H2O)3]·(H2O)9.5, while the pH adjustment with NH3 resulted in [Ce6(μ3-O)4(μ3-OH)4(HCOO)10(NO3)4]·(NO3)3(NH4)5(H2O)5. Furthermore, the crystal structure of Ce(III) formate, Ce(HCOO)3, was determined. The coordination polyhedron is a tricapped trigonal prism which is formed exclusively by nine HCOO(-) ligands. The hexanuclear Ce(IV) formate species from aqueous solution is widely preserved in the crystal structure, whereas the mononuclear solution species of Ce(III) formate undergoes a polymerization during the crystallization process.

Synthesis and characterization of tetraacetonitrilolithiumhexafluorophosphate crystal

NASA Astrophysics Data System (ADS)

Li, Xuecong; Li, Xuanli; Zhang, Zhiye; Yang, Lin; Zhong, Benhe; Wang, Xinlong

2015-08-01

Tetraacetonitrilolithiumhexafluorophosphate (Li(CH3CN)4PF6) crystal is an important intermediate in the preparation of high purity lithium hexafluorophosphate electrolyte via a simple transformation method. In this study, the crystal parameters were determined by X-ray powder diffraction analysis, which showed that it belongs to the triclinic system with space group P1. FTIR spectral studies identified the characteristic absorption bands of Ctbnd N and PF6- in the synthesized complex. Chemical analysis, gas chromatography, and ICP-AES results showed that the elementary ratio of Li:P:F: CH3CN in the complex is approximately: 1:1:6:4. Furthermore, the geometric optimization structure of Li(CH3CN)4PF6 was obtained using GAUSSIAN 09 program on a B3LYP/6-31+G(d, p) level. In this structure, two acetonitrile ligands bind strongly with the Li+ ion, whereas the other two are weakly-coordinated with lithium. The results of solid-state 13C-, 31P-, and 19F-NMR spectra confirmed that this configuration is reasonable.

Crystal structure of 6-chloro-5-iso-propyl-pyrimidine-2,4(1H,3H)-dione.

PubMed

Haress, Nadia G; Ghabbour, Hazem A; El-Emam, Ali A; Chidan Kumar, C S; Fun, Hoong-Kun

2014-11-01

In the mol-ecule of the title compound, C7H9ClN2O2, the conformation is determined by intra-molecular C-H⋯O and C-H⋯Cl hydrogen bonds, which generate S(6) and S(5) ring motifs. The isopropyl group is almost perpendicular to the pyrimidine ring with torsion angles of -70.8 (3) and 56.0 (3)°. In the crystal, two inversion-related mol-ecules are linked via a pair of N-H⋯O hydrogen bonds into R 2 (2)(8) dimers; these dimers are connected into chains extending along the bc plane via an additional N-H⋯O hydrogen bond and weaker C-H⋯O hydrogen bonds. The crystal structure is further stabilized by a weak π-π inter-action [3.6465 (10) Å] between adjacent pyrimidine-dione rings arranged in a head-to-tail fashion, producing a three-dimensional network.

A low-temperature polymorph of m-quinquephenyl.

PubMed

Gomes, Ligia R; Howie, R Alan; Low, John Nicolson; Rodrigues, Ana S M C; Santos, Luís M N B F

2012-12-01

A low-temperature polymorph of 1,1':3',1'':3'',1''':3''',1''''-quinquephenyl (m-quinquephenyl), C(30)H(22), crystallizes in the space group P2(1)/c with two molecules in the asymmetric unit. The crystal is a three-component nonmerohedral twin. A previously reported room-temperature polymorph [Rabideau, Sygula, Dhar & Fronczek (1993). Chem. Commun. pp. 1795-1797] also crystallizes with two molecules in the asymmetric unit in the space group P-1. The unit-cell volume for the low-temperature polymorph is 4120.5 (4) Å(3), almost twice that of the room-temperature polymorph which is 2102.3 (6) Å(3). The molecules in both structures adopt a U-shaped conformation with similar geometric parameters. The structural packing is similar in both compounds, with the molecules lying in layers which stack perpendicular to the longest unit-cell axis. The molecules pack alternately in the layers and in the stacked columns. In both polymorphs, the only interactions between the molecules which can stabilize the packing are very weak C-H...π interactions.

Synthesis, characterization, crystal structure and DFT study of two new polymorphs of a Schiff base (E)-2-((2,6-dichlorobenzylidene)amino)benzonitrile

NASA Astrophysics Data System (ADS)

Benarous, N.; Cherouana, A.; Aubert, Emmanuel; Durand, Pierrick; Dahaoui, S.

2016-02-01

Two new polymorphs of Schiff base, (E)-2-((2,6-dichlorobenzylidene)amino)benzonitrile, were prepared from the condensation of 4-amino-benzonitrile and 2,6-dichlorobenzaldehyde. The two polymorphs crystallize in two different space groups: P21/c for polymorph (I) with volume 1264.23(2) Å3 and Pbca for polymorph (II) with volume 2469.3(2) Å3. The two polymorphs have been characterized by FT-IR and UV-VIS spectroscopy. The crystal structures of both compounds were determined by single X-ray analysis. The difference between the two polymorphs was observed at the angle between the two phenyl rings which is 4.81° for the first one and 82.27° for the second one. Both crystal structures are built on the basis of moderate and weak hydrogen bonds. Theoretical calculations on isolated molecules at the MP2 cc-pVDZ level show that the two polymorphs correspond to two molecular conformations that are within less than 1 kJ mol-1 and DFT periodic calculations indicate that (II) is more stable than (I) by 4.1 kJ mol-1 of formula unit. Additionally, we performed TD-DFT calculation for free ligands to support the experimental data.

Guiding, bending, and splitting of coupled defect surface modes in a surface-wave photonic crystal

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gao, Zhen; Gao, Fei; Zhang, Baile, E-mail: blzhang@ntu.edu.sg

2016-01-25

We experimentally demonstrate a type of waveguiding mechanism for coupled surface-wave defect modes in a surface-wave photonic crystal. Unlike conventional spoof surface plasmon waveguides, waveguiding of coupled surface-wave defect modes is achieved through weak coupling between tightly localized defect cavities in an otherwise gapped surface-wave photonic crystal, as a classical wave analogue of tight-binding electronic wavefunctions in solid state lattices. Wave patterns associated with the high transmission of coupled defect surface modes are directly mapped with a near-field microwave scanning probe for various structures including a straight waveguide, a sharp corner, and a T-shaped splitter. These results may find usemore » in the design of integrated surface-wave devices with suppressed crosstalk.« less

The role of order-disorder transitions in the quest for molecular multiferroics: structural and magnetic neutron studies of a mixed valence iron(II)-iron(III) formate framework.

PubMed

Cañadillas-Delgado, Laura; Fabelo, Oscar; Rodríguez-Velamazán, J Alberto; Lemée-Cailleau, Marie-Hélène; Mason, Sax A; Pardo, Emilio; Lloret, Francesc; Zhao, Jiong-Peng; Bu, Xian-He; Simonet, Virginie; Colin, Claire V; Rodríguez-Carvajal, Juan

2012-12-05

Neutron diffraction studies have been carried out to shed light on the unprecedented order-disorder phase transition (ca. 155 K) observed in the mixed-valence iron(II)-iron(III) formate framework compound [NH(2)(CH(3))(2)](n)[Fe(III)Fe(II)(HCOO)(6)](n). The crystal structure at 220 K was first determined from Laue diffraction data, then a second refinement at 175 K and the crystal structure determination in the low temperature phase at 45 K were done with data from the monochromatic high resolution single crystal diffractometer D19. The 45 K nuclear structure reveals that the phase transition is associated with the order-disorder of the dimethylammonium counterion that is weakly anchored in the cavities of the [Fe(III)Fe(II)(HCOO)(6)](n) framework. In the low-temperature phase, a change in space group from P31c to R3c occurs, involving a tripling of the c-axis due to the ordering of the dimethylammonium counterion. The occurrence of this nuclear phase transition is associated with an electric transition, from paraelectric to antiferroelectric. A combination of powder and single crystal neutron diffraction measurements below the magnetic order transition (ca. 37 K) has been used to determine unequivocally the magnetic structure of this Néel N-Type ferrimagnet, proving that the ferrimagnetic behavior is due to a noncompensation of the different Fe(II) and Fe(III) magnetic moments.

Crystal structure and theoretical studies of derivative of imidazo-1,2,4-triazine

NASA Astrophysics Data System (ADS)

Dybała, Izabela; Sztanke, Krzysztof

2016-09-01

In this study, we present the result of X-ray structure analysis of methyl [8-(3-chlorophenyl)-4-oxo-2,3,4,6,7,8-heksahydroimidazo[2,1-c][1,2,4]triazin-3-yl]acetate (1). The molecule conformation is flat, with a chlorophenyl substituent and the ester moiety lying in the plain of the heterobicyclic scaffold. Its conformation is stabilized by an intramolecular Nsbnd H…O hydrogen bond. Within the crystalline structure of 1, molecules associate with one another by weak Csbnd H…O, Csbnd H…Cl and Csbnd H…π bonds. The molecular and crystal structure of 1 was compared with the previously described structurally similar compound possessing the same bicyclic rigid core and similar chemical nature of the functional ester moiety. Very interesting differences in molecules geometry and association were observed. Non-covalent bonds within the crystals are additionally visualized by determination of Hirshfeld surfaces. Moreover, the quantum chemical calculation for 1 in the gas phase were carried out. The DFT calculation methods was used to optimize of molecule geometry and obtain molecular energy profiles with respect to selected torsion angles. The quantum chemical conformational analysis that was carried out for compound 1 in the gas phase suggests that in the solid state the molecules adopt the minimum energy conformation.

Rattling induced superconductivity in RV2Al20 (R = Sc, Lu, Y) aluminides - an experimental and theoretical study

NASA Astrophysics Data System (ADS)

Winiarski, Michal; Wiendlocha, Bartlomiej; Sternik, Malgorzata; Wisniewski, Piotr; Kaczorowski, Dariusz; Klimczuk, Tomasz

Polycrystalline samples of four ternary intermetallics RV2Al20 (R = Sc, Y, La, and Lu) were synthesized. Structural studies carried out using powder x-ray diffraction and Rietveld analysis show that all compounds crystallize in CeCr2Al20-type structure composed of icosahedral Al-R cages. Results of physical properties measurements reveal that ScV2Al20, YV2Al20, and LuV2Al20 are weakly-coupled BCS superconductors with critical temperatures Tc = 1.0, 0.57, and 0.60 K, respectively. Electronic and phonon structure calculations reveal the key role of low-frequency anharmonic vibrations of R atoms (rattling effect) for the appearance of superconductivity. A correlation between phonon and crystal structures was observed, allowing to search for new RV2Al20 superconductors. Project was financially supported by the National Science Centre (Poland) Grant (DEC-2012/07/E/ST3/00584).

Minor groove binding of a bis-quaternary ammonium compound: the crystal structure of SN 7167 bound to d(CGCGAATTCGCG)2.

PubMed Central

Squire, C J; Clark, G R; Denny, W A

1997-01-01

The X-ray crystal structure of the complex between the synthetic antitumour and antiviral DNA binding ligand SN 7167 and the DNA oligonucleotide d(CGCGAATTCGCG)2 has been determined to an R factor of 18.3% at 2.6 A resolution. The ligand is located within the minor groove and covers almost 6 bp with the 1-methylpyridinium ring extending as far as the C9-G16 base pair and the 1-methylquinolinium ring lying between the G4-C21 and A5-T20 base pairs. The ligand interacts only weakly with the DNA, as evidenced by long range contacts and shallow penetration into the groove. This structure is compared with that of the complex between the parent compound SN 6999 and the alkylated DNA sequence d(CGC[e6G]AATTCGCG)2. There are significant differences between the two structures in the extent of DNA bending, ligand conformation and groove binding. PMID:9321660

Crystal structure of the pyrochlore oxide superconductor KOs{sub 2}O{sub 6}

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yamaura, Jun-Ichi; Yonezawa, Shigeki; Muraoka, Yuji

2006-01-15

We report the single-crystal X-ray analysis of the structure of the pyrochlore oxide superconductor KOs{sub 2}O{sub 6}. The structure was identified as the {beta}-pyrochlore structure with space group Fd3-bar m and lattice constant a=10.089(2)A at 300K: the K atom is located at the 8b site, not at the 16d site as in conventional pyrochlore oxides. We found an anomalously large atomic displacement parameter U{sub iso}=0.0735(8)A{sup 2} at 300K for the K cation, which suggests that the K cation weakly bound to an oversized Os{sub 12}O{sub 18} cage exhibits intensive rattling, as recently observed for clathrate compounds. The rattling of Amore » cations is a common feature in the series of {beta}-pyrochlore oxide superconductors AOs{sub 2}O{sub 6} (A=Cs, Rb and K), and is greatest for the smallest K cation.« less

Pressure-induced organic topological nodal-line semimetal in the three-dimensional molecular crystal Pd (dddt) 2

NASA Astrophysics Data System (ADS)

Liu, Zhao; Wang, Haidi; Wang, Z. F.; Yang, Jinlong; Liu, Feng

2018-04-01

The nodal-line semimetal represents a class of topological materials characterized with highest band degeneracy. It is usually found in inorganic materials of high crystal symmetry or a minimum symmetry of inversion aided with accidental band degeneracy [Phys. Rev. Lett. 118, 176402 (2017), 10.1103/PhysRevLett.118.176402]. Based on first-principles band structure, Wannier charge center, and topological surface state calculations, here we predict a pressure-induced topological nodal-line semimetal in the absence of spin-orbit coupling (SOC) in the synthesized single-component 3D molecular crystal Pd (dddt) 2 . We show a Γ -centered single nodal line undulating within a narrow energy window across the Fermi level. This intriguing nodal line is generated by pressure-induced accidental band degeneracy, without protection from any crystal symmetry. When SOC is included, the fourfold degenerated nodal line is gapped and Pd (dddt) 2 becomes a strong 3D topological metal with an Z2 index of (1;000). However, the tiny SOC gap makes it still possible to detect the nodal-line properties experimentally. Our findings afford an attractive route for designing and realizing topological states in 3D molecular crystals, as they are weakly bonded through van der Waals forces with a low crystal symmetry so that their electronic structures can be easily tuned by pressure.

Crystal structure of 1,3-bis-(1H-benzotriazol-1-yl-meth-yl)benzene.

PubMed

Macías, Mario A; Nuñez-Dallos, Nelson; Hurtado, John; Suescun, Leopoldo

2016-06-01

The mol-ecular structure of the title compound, C20H16N6, contains two benzotriazole units bonded to a benzene nucleus in a meta configuration, forming dihedral angles of 88.74 (11) and 85.83 (10)° with the central aromatic ring and 57.08 (9)° with each other. The three-dimensional structure is controlled mainly by weak C-H⋯N and C-H⋯π inter-actions. The mol-ecules are connected in inversion-related pairs, forming the slabs of infinite chains that run along the [-110] and [110] directions.

New vanadium tellurites: Syntheses, structures, optical properties of noncentrosymmetric VTeO{sub 4}(OH), centrosymmetric Ba{sub 2}V{sub 4}O{sub 8}(Te{sub 3}O{sub 10})

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liang, Ming-Li; State Key Laboratory of Structural Chemistry, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Fuzhou 350002; Marsh, Matthew

Two new vanadium tellurites, VTeO{sub 4}(OH) (1) and Ba{sub 2}V{sub 4}O{sub 8}(Te{sub 3}O{sub 10}) (2), have been synthesized successfully with the use of hydrothermal reactions. The crystal structures of the two compounds were determined by single-crystal X-ray diffraction. Compound 1 crystallizes in the polar space group Pca2{sub 1} (No. 29) while compound 2 crystallizes in the centrosymmetric space group C2/c (No. 15). The topography of compound 1 reveals a two-dimensional, layered structure comprised of VO{sub 6} octahedral chains and TeO{sub 3}(OH) zig-zag chains. Compound 2, on the contrary, features a three-dimensional [V{sub 4}O{sub 8}(Te{sub 3}O{sub 10})]{sup 4-} anionic framework withmore » Ba{sup 2+} ions filled into the 10-member ring helical tunnels. The [V{sub 4}O{sub 8}(Te{sub 3}O{sub 10})]{sup 4-} anionic network is the first 3D vanadium tellurite framework to be discovered in the alkaline-earth vanadium tellurite system. Powder second harmonic generation (SHG) measurements indicate that compound 1 shows a weak SHG response of about 0.3×KDP (KH{sub 2}PO{sub 4}) under 1064 nm laser radiation. Infrared spectroscopy, elemental analysis, thermal analysis, and dipole moment calculations have also been carried out. - Graphical abstract: VTeO{sub 4}(OH) (1) crystallizes in the noncentrosymmetric space group Pca2{sub 1} (No. 29) while Ba{sub 2}V{sub 4}O{sub 8}(Te{sub 3}O{sub 10}) (2) crystallizes in the centrosymmetric space group C2/c (No. 15). - Highlights: • VTeO{sub 4}(OH) (1) and Ba{sub 2}V{sub 4}O{sub 8}(Te{sub 3}O{sub 10}) (2) have been synthesized successfully with the use of hydrothermal reactions. • VTeO{sub 4}(OH) (1) crystallizes in the noncentrosymmetric space group Pca2{sub 1} and displays a weak SHG response. • VTeO{sub 4}(OH) (1) represents only the fourth SHG-active material found in vanadium tellurite systems. • Ba{sub 2}V{sub 4}O{sub 8}(Te{sub 3}O{sub 10}) (2) exhibits a novel three-dimensional [V{sub 4}O{sub 8}(Te{sub 3}O{sub 10})]{sup 4-} anionic framework.« less

Experimental and computational studies on creatininium 4-nitrobenzoate - An organic proton transfer complex

NASA Astrophysics Data System (ADS)

Thirumurugan, R.; Anitha, K.

2017-10-01

A new organic proton transfer complex of creatininium 4-nitrobenzoate (C4NB) has been synthesized and its single crystals were grown successfully by slow evaporation technique. The grown single crystal was subjected to various characterization techniques like single crystal X-ray diffraction (SCXRD), FTIR, FT-Raman and Kurtz-Perry powder second harmonic generation (SHG). The SCXRD analysis revealed that C4NB was crystallized into orthorhombic crystal system, with noncentrosymmetric (NCS), P212121 space group. The creatininium cation and 4-nitrobenzoate anion were connected through a pair of N__H⋯O hydrogen bonds (N(3)__H(6) ⋯ O(3) (x+1, y, z) and N(2)__H(5) &ctdot O(2) (x-1/2, -y-1/2, -z+2)) and fashioned a R22(8) ring motif. The crystal structure was stabilized by strong N__H⋯O and weak C__H⋯O intermolecular interactions and it was quantitatively analysed by Hirshfeld surface and fingerprint (FP) analysis. FTIR and FT-Raman studies confirmed the vibrational modes of functional groups present in C4NB compound indubitably. SHG efficiency of grown crystal was 4.6 times greater than that of standard potassium dihydrogen phosphate (KDP) material. Moreover, density functional theory (DFT) studies such as Mulliken charge distribution, frontier molecular orbitals (FMOs), molecular electrostatic potential (MEP) map, natural bond orbital analysis (NBO) and first order hyperpolarizability (β0) were calculated to explore the structure-property relationship.

Crystal structure of 1-(3-chloro­phen­yl)piperazin-1-ium picrate–picric acid (2/1)

PubMed Central

Kavitha, Channappa N.; Jasinski, Jerry P.; Kaur, Manpreet; Anderson, Brian J.; Yathirajan, H. S.

2014-01-01

The title salt {systematic name: bis­[1-(3-chloro­phen­yl)piperazinium 2,4,6-tri­nitro­phenolate]–picric acid (2/1)}, 2C10H14ClN2 +·2C6H5N3O7 −·C6H6N3O7, crystallized with two independent 1-(3-chloro­phen­yl)piperazinium cations, two picrate anions and a picric acid mol­ecule in the asymmetric unit. The six-membered piperazine ring in each cation adopts a slightly distorted chair conformation and contains a protonated N atom. In the picric acid mol­ecule, the mean planes of the nitro groups in the ortho-, meta-, and para-positions are twisted from the benzene ring by 31.5 (3), 7.7 (1), and 3.8 (2)°, respectively. In the anions, the dihedral angles between the benzene ring and the ortho-, meta-, and para-nitro groups are 36.7 (1), 5.0 (6), 4.8 (2)°, and 34.4 (9), 15.3 (8), 4.5 (1)°, respectively. The nitro group in one anion is disordered and was modeled with two sites for one O atom with an occupancy ratio of 0.627 (7):0.373 (7). In the crystal, the picric acid mol­ecule inter­acts with the picrate anion through a trifurcated O—H⋯O four-centre hydrogen bond involving an intra­molecular O—H⋯O hydrogen bond and a weak C—H⋯O inter­action. Weak inter­molecular C—H⋯O inter­actions are responsible for the formation of cation–anion–cation trimers resulting in a chain along [010]. In addition, weak C—H⋯Cl and weak π–π inter­actions [centroid–centroid distances of 3.532 (3), 3.756 (4) and 3.705 (3) Å] are observed and contribute to the stability of the crystal packing. PMID:25484834

Structural and optical properties of indium-doped highly conductive ZnO bulk crystals grown by the hydrothermal technique

NASA Astrophysics Data System (ADS)

Wang, Buguo; Claflin, Bruce; Look, David; Jiménez, Juan

2018-02-01

Indium-doped ZnO bulk crystals grown by the hydrothermal method are highly-conductive, with resistivity at 0.01 Ωcm at room temperature as revealed by Hall-effect measurement. In this paper we report on structural and optical properties of these crystals. The grown In:ZnO crystals have been studied by high resolution X-ray diffraction, micro-Raman scattering and low-temperature photoluminescence and cathodoluminescence. It was found that the c lattice parameter of the grown In:ZnO crystal expanded 0.06% with respect to the lithium-doped ZnO crystal seed, and the In-doped ZnO overgrew the seed crystal pseudomorphically but with high quality crystallinity; the X-ray rocking curves show the FWHM of the Zn face and O faces are only 0.05° and 0.1° ; and the indium concentration in the crystal reaches the solubility limit. Raman spectra show strain relaxation gradually from the regrowth interface as well as a weak spectral feature at 723 cm-1. The peak at 312 cm-1 noticed in hydrothermally grown In:ZnO nanostructures does not appear in our In-doped crystals, indicating that this peak may be associated with specific defects (e.g. surface related) of the nanostructures. Photoluminescence measurements show that an indium donor bound exciton peak I9 (In0X) is the dominant peak in the PL spectrum, located at 3.3586 eV on the zinc face and 3.3577 eV on the oxygen face. Both of them deviated from the consensus literature value of 3.3567 eV, probably due to strain in the crystal induced by impurities.

The structure of and origin of nodular chromite from the Troodos ophiolite, Cyprus, revealed using high-resolution X-ray computed tomography and electron backscatter diffraction

NASA Astrophysics Data System (ADS)

Prichard, H. M.; Barnes, S. J.; Godel, B.; Reddy, S. M.; Vukmanovic, Z.; Halfpenny, A.; Neary, C. R.; Fisher, P. C.

2015-03-01

Nodular chromite is a characteristic feature of ophiolitic podiform chromitite and there has been much debate about how it forms. Nodular chromite from the Troodos ophiolite in Cyprus is unusual in that it contains skeletal crystals enclosed within the centres of the nodules and interstitial to them. 3D imaging and electron backscatter diffraction have shown that the skeletal crystals within the nodules are single crystals that are surrounded by a rim of polycrystalline chromite. 3D analysis reveals that the skeletal crystals are partially or completely formed cage or hopper structures elongated along the < 111 > axis. The rim is composed of a patchwork of chromite grains that are truncated on the outer edge of the rim. The skeletal crystals formed first from a magma supersaturated in chromite and silicate minerals crystallised from melt trapped between the chromite skeletal crystal blades as they grew. The formation of skeletal crystals was followed by a crystallisation event which formed a silicate-poor rim of chromite grains around the skeletal crystals. These crystals show a weak preferred orientation related to the orientation of the core skeletal crystal implying that they formed by nucleation and growth on this core, and did not form by random mechanical aggregation. Patches of equilibrium adcumulate textures within the rim attest to in situ development of such textures. The nodules were subsequently exposed to chromite undersaturated magma resulting in dissolution, recorded by truncated grain boundaries in the rim and a smooth outer surface to the nodule. None of these stages of formation require a turbulent magma. Lastly the nodules impinged on each other causing local deformation at points of contact.

Role of Polymorphism and Thin-Film Morphology in Organic Semiconductors Processed by Solution Shearing

PubMed Central

2018-01-01

Organic semiconductors (OSCs) are promising materials for cost-effective production of electronic devices because they can be processed from solution employing high-throughput techniques. However, small-molecule OSCs are prone to structural modifications because of the presence of weak van der Waals intermolecular interactions. Hence, controlling the crystallization in these materials is pivotal to achieve high device reproducibility. In this perspective article, we focus on controlling polymorphism and morphology in small-molecule organic semiconducting thin films deposited by solution-shearing techniques compatible with roll-to-roll systems. Special attention is paid to the influence that the different experimental deposition parameters can have on thin films. Further, the main characterization techniques for thin-film structures are reviewed, highlighting the in situ characterization tools that can provide crucial insights into the crystallization mechanisms. PMID:29503976

Spectroscopic study of uracil, 1-methyluracil and 1-methyl-4-thiouracil: Hydrogen bond interactions in crystals and ab-initio molecular dynamics

NASA Astrophysics Data System (ADS)

Brela, Mateusz Z.; Boczar, Marek; Malec, Leszek M.; Wójcik, Marek J.; Nakajima, Takahito

2018-05-01

Hydrogen bond networks in uracil, 1-methyluracil and 1-methyl-4-thiouracil were studied by ab initio molecular dynamics as well as analysis of the orbital interactions. The power spectra calculated by ab initio molecular dynamics for atoms involved in hydrogen bonds were analyzed. We calculated spectra by using anharmonic approximation based on the autocorrelation function of the atom positions obtained from the Born-Oppenheimer simulations. Our results show the differences between hydrogen bond networks in uracil and its methylated derivatives. The studied methylated derivatives, 1-methyluracil as well as 1-methyl-4-thiouracil, form dimeric structures in the crystal phase, while uracil does not form that kind of structures. The presence of sulfur atom instead oxygen atom reflects weakness of the hydrogen bonds that build dimers.

A weak electric field-assisted ultrafast electrical switching dynamics in In3SbTe2 phase-change memory devices

NASA Astrophysics Data System (ADS)

Pandey, Shivendra Kumar; Manivannan, Anbarasu

2017-07-01

Prefixing a weak electric field (incubation) might enhance the crystallization speed via pre-structural ordering and thereby achieving faster programming of phase change memory (PCM) devices. We employed a weak electric field, equivalent to a constant small voltage (that is incubation voltage, Vi of 0.3 V) to the applied voltage pulse, VA (main pulse) for a systematic understanding of voltage-dependent rapid threshold switching characteristics and crystallization (set) process of In3SbTe2 (IST) PCM devices. Our experimental results on incubation-assisted switching elucidate strikingly one order faster threshold switching, with an extremely small delay time, td of 300 ps, as compared with no incubation voltage (Vi = 0 V) for the same VA. Also, the voltage dependent characteristics of incubation-assisted switching dynamics confirm that the initiation of threshold switching occurs at a lower voltage of 0.82 times of VA. Furthermore, we demonstrate an incubation assisted ultrafast set process of IST device for a low VA of 1.7 V (˜18 % lesser compared to without incubation) within a short pulse-width of 1.5 ns (full width half maximum, FWHM). These findings of ultrafast switching, yet low power set process would immensely be helpful towards designing high speed PCM devices with low power operation.

Possible Mechanisms for Turbofan Engine Ice Crystal Icing at High Altitude

NASA Technical Reports Server (NTRS)

Tsao, Jen-Ching; Struk, Peter M.; Oliver, Michael

2014-01-01

A thermodynamic model is presented to describe possible mechanisms of ice formation on unheated surfaces inside a turbofan engine compression system from fully glaciated ice crystal clouds often formed at high altitude near deep convective weather systems. It is shown from the analysis that generally there could be two distinct types of ice formation: (1) when the "surface freezing fraction" is in the range of 0 to 1, dominated by the freezing of water melt from fully or partially melted ice crystals, the ice structure is formed from accretion with strong adhesion to the surface, and (2) when the "surface melting fraction" is the range of 0 to 1, dominated by the further melting of ice crystals, the ice structure is formed from accumulation of un-melted ice crystals with relatively weak bonding to the surface. The model captures important qualitative trends of the fundamental ice-crystal icing phenomenon reported earlier1,2 from the research collaboration work by NASA and the National Research Council (NRC) of Canada. Further, preliminary analysis of test data from the 2013 full scale turbofan engine ice crystal icing test3 conducted in the NASA Glenn Propulsion Systems Laboratory (PSL) has also suggested that (1) both types of ice formation occurred during the test, and (2) the model has captured some important qualitative trend of turning on (or off) the ice crystal ice formation process in the tested engine low pressure compressor (LPC) targeted area under different icing conditions that ultimately would lead to (or suppress) an engine core roll back (RB) event.

Possible Mechanisms for Turbofan Engine Ice Crystal Icing at High Altitude

NASA Technical Reports Server (NTRS)

Tsao, Jen-Ching; Struk, Peter M.; Oliver, Michael J.

2016-01-01

A thermodynamic model is presented to describe possible mechanisms of ice formation on unheated surfaces inside a turbofan engine compression system from fully glaciated ice crystal clouds often formed at high altitude near deep convective weather systems. It is shown from the analysis that generally there could be two distinct types of ice formation: (1) when the "surface freezing fraction" is in the range of 0 to 1, dominated by the freezing of water melt from fully or partially melted ice crystals, the ice structure is formed from accretion with strong adhesion to the surface, and (2) when the "surface melting fraction" is the range of 0 to 1, dominated by the further melting of ice crystals, the ice structure is formed from accumulation of un-melted ice crystals with relatively weak bonding to the surface. The model captures important qualitative trends of the fundamental ice-crystal icing phenomenon reported earlier (Refs. 1 and 2) from the research collaboration work by NASA and the National Research Council (NRC) of Canada. Further, preliminary analysis of test data from the 2013 full scale turbofan engine ice crystal icing test (Ref. 3) conducted in the NASA Glenn Propulsion Systems Laboratory (PSL) has also suggested that (1) both types of ice formation occurred during the test, and (2) the model has captured some important qualitative trend of turning on (or off) the ice crystal ice formation process in the tested engine low pressure compressor (LPC) targeted area under different icing conditions that ultimately would lead to (or suppress) an engine core roll back (RB) event.

(4S,5S,6S)-4-Hy­droxy-3-meth­oxy-5-methyl-5,6-ep­oxy­cyclo­hex-2-en-1-one

PubMed Central

Tansuwan, Srinuan; Chanaprat, Porntana; Teerawatananond, Thapong; Muangsin, Nongnuj; Pornpakakul, Surachai

2010-01-01

The title compound, C8H10O4, was isolated from culture extracts of the endophytic fungus Xylaria sp. (PB-30). The cyclo­hexenone ring exhibits a flattened boat conformation. In the crystal structure, mol­ecules related by translation along the b axis are linked into chains through O—H⋯O hydrogen bonds. Weak non-classical C—H⋯O contacts are also observed in the structure. PMID:21588622

Study of a structural phase transition by two dimensional Fourier transform NMR method

NASA Astrophysics Data System (ADS)

Trokiner, A.; Man, P. P.; Théveneau, H.; Papon, P.

1985-09-01

The fluoroperovskite RbCaF 3 undergoes a structural phase transition at 195.5 K, from a cubic phase where the 87Rb nuclei have no quadrupolar interaction ( ωQ= 0) to a tetragonal phase where ω Q ≠ O. The transition is weakly first-order. A two-dimensional FT NMR experiment has been performed on 87Rb ( I = {3}/{2}) in a single crystal in both phases and in the vicinity of the phase transition. Our results show the coexistence of the two phases at the phase transition.

Chloridotetra­kis(pyridine-4-carb­alde­hyde-κN)copper(II) chloride

PubMed Central

Meng, Xiu-Jin; Zhang, Shu-Hua; Yang, Ge-Ge; Huang, Xue-Ren; Jiang, Yi-Min

2009-01-01

In the mol­ecular structure of the title compound, [CuCl(C6H5NO)4]Cl, the CuII atom is coordinated by four N atoms of four pyridine-4-carboxaldehyde ligands and one chloride anion in a slightly distorted square-pyramidal coordination geometry. There is also a non-coordinating Cl− anion in the crystal structure. The CuII atom and both Cl atoms are situated on fourfold rotation axes. A weak C—H⋯Cl inter­action is also present. PMID:21578129

Preparation, Crystal Structure, Dielectric Properties, and Magnetic Behavior of Ba 2Fe 2Ti 4O 13

NASA Astrophysics Data System (ADS)

Vanderah, T. A.; Huang, Q.; Wong-Ng, W.; Chakoumakos, B. C.; Goldfarb, R. B.; Geyer, R. G.; Baker-Jarvis, J.; Roth, R. S.; Santoro, A.

1995-11-01

The preparation, crystal structure, dielectric properties, and magnetic behavior of the new compound Ba2Fe2Ti4O13 are reported. Structural studies carried out by single-crystal X-ray diffraction and neutron powder diffraction show that this phase is isostructural with K2Ti6O13 and Ba2ZnTi5O13 (C2/m (No. 12); a = 15.216(1), b = 3.8979(3), c = 9.1350(6) Å, β = 98.460(7)°; V = 535.90(8) Å3; Z = 2). The cations Fe3+ and Ti4+ are partially ordered among distorted octahedral sites with Ba2+ occupying eleven-coordinated polyhedra. Ba2Fe2Ti4O13 exhibits TE0 resonance near 10 GHz with a dielectric constant of ∼28 and a dielectric loss tangent of 2 × 10-3. The compound displays complex paramagnetic behavior with marked field dependence; the magnetization at 80 kA/m is several orders of magnitude smaller than that of most ferrites. Spin-glass effects have not been observed; however, weak collective interactions are clearly present. No magnetic ordering has been detected by neutron diffraction down to 13 K.

Optical study of Tm-doped solid solution (Sc0.5Y0.5)2SiO5 crystal

NASA Astrophysics Data System (ADS)

Shi, Jiaojiao; Liu, Bin; Zheng, Lihe; Wang, Qingguo; Tang, Huili; Liu, Junfang; Su, Liangbi; Wu, Feng; Zhao, Hengyu; He, Nuotian; Li, Na; Li, Qiu; Guo, Chao; Xu, Jun; Yang, Kejian; Xu, Xiaodong; Ryba-Romanowski, Witold; Lisiecki, Radosław; Solarz, Piotr

2018-04-01

Tm-doped (Sc0.5Y0.5)2SiO5 (SYSO) crystals were grown by Czochralski method. The UV-VIR-NIR absorption spectra and the near-infrared emission spectra were measured and analysed by the Judd-Ofelt approach. Temperature influence on both absorption and emission spectra has been determined from the data recorded at room temperature and 10 K. It has been found that the structural disorder resulting from dissimilar ionic radii of Sc3+ and Y3+ in the solid solution (Sc0.5Y0.5)2SiO5 crystal brings about a strong inhomogeneous broadening of Tm3+ ions spectra. However, it affects the excited state relaxation dynamics inherent to thulium-doped Y2SiO5 and Sc2SiO5 hosts weakly.

Multi-crystal native SAD analysis at 6 keV.

PubMed

Liu, Qun; Guo, Youzhong; Chang, Yanqi; Cai, Zheng; Assur, Zahra; Mancia, Filippo; Greene, Mark I; Hendrickson, Wayne A

2014-10-01

Anomalous diffraction signals from typical native macromolecules are very weak, frustrating their use in de novo structure determination. Here, native SAD procedures are described to enhance signal to noise in anomalous diffraction by using multiple crystals in combination with synchrotron X-rays at 6 keV. Increased anomalous signals were obtained at 6 keV compared with 7 keV X-ray energy, which was used for previous native SAD analyses. A feasibility test of multi-crystal-based native SAD phasing was performed at 3.2 Å resolution for a known tyrosine protein kinase domain, and real-life applications were made to two novel membrane proteins at about 3.0 Å resolution. The three applications collectively serve to validate the robust feasibility of native SAD phasing at lower energy.

Crystal structure of 3-{[4-(2-meth-oxy-phen-yl)piperazin-1-yl]meth-yl}-5-(thio-phen-2-yl)-1,3,4-oxa-diazole-2(3H)-thione.

PubMed

Al-Alshaikh, Monirah A; Abuelizz, Hatem A; El-Emam, Ali A; Abdelbaky, Mohammed S M; Garcia-Granda, Santiago

2016-02-01

The title compound, C18H20N4O2S2, is a new 1,3,4-oxa-diazole and a key pharmacophore of several biologically active agents. It is composed of a meth-yl(thio-phen-2-yl)-1,3,4-oxa-diazole-2(3H)-thione moiety linked to a 2-meth-oxy-phenyl unit via a piperazine ring that has a chair conformation. The thio-phene ring mean plane lies almost in the plane of the oxa-diazole ring, with a dihedral angle of 4.35 (9)°. The 2-meth-oxy-phenyl ring is almost normal to the oxa-diazole ring, with a dihedral angle of 84.17 (10)°. In the crystal, mol-ecules are linked by weak C-H⋯S hydrogen bonds and C-H⋯π inter-actions, forming layers parallel to the bc plane. The layers are linked via weak C-H⋯O hydrogen bonds and slipped parallel π-π inter-actions [inter-centroid distance = 3.6729 (10) Å], forming a three-dimensional structure. The thio-phene ring has an approximate 180° rotational disorder about the bridging C-C bond.

Fullerene (C60) films for solid lubrication

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bhushan, B.; Gupta, B.K.; Van Cleef, G.W.

1993-10-01

The advent of techniques for producing gram quantities of a new form of stable, pure, solid carbon, designated as fullerene, opens a profusion of possibilities to be explored in many disciplines including tribology. Fullerenes take the form of hollow geodesic domes, which are formed from a network of pentagons and hexagons with covalently bonded carbon atoms. The C60 molecule has the highest possible symmetry (icosahedral) and assumes the shape of a soccer ball. At room temperature, fullerene molecules pack in an fcc lattice bonded with weak van der Waals attractions. Fullerenes can be dissolved in solvents such as toluene andmore » benzene and are easily sublimed. The low surface energy, high chemical stability, spherical shape, weak intermolecular bonding, and high load bearing capacity of C60 molecules offer potential for various mechanical and tribological applications. This paper describes the crystal structure and properties of fullerenes and proposes a mechanism for self-lubricating action. Sublimed films of C60 have been produced and friction and wear performance of these films in various operating environments are the subject of this paper. The results of this study indicate that C60, owing to its unique crystal structure and bonding, may be a promising solid lubricant. 31 refs.« less

Localization and orientation of heavy-atom cluster compounds in protein crystals using molecular replacement

PubMed Central

Dahms, Sven O.; Kuester, Miriam; Streb, Carsten; Roth, Christian; Sträter, Norbert; Than, Manuel E.

2013-01-01

Heavy-atom clusters (HA clusters) containing a large number of specifically arranged electron-dense scatterers are especially useful for experimental phase determination of large complex structures, weakly diffracting crystals or structures with large unit cells. Often, the determination of the exact orientation of the HA cluster and hence of the individual heavy-atom positions proves to be the critical step in successful phasing and subsequent structure solution. Here, it is demonstrated that molecular replacement (MR) with either anomalous or isomorphous differences is a useful strategy for the correct placement of HA cluster compounds. The polyoxometallate cluster hexasodium α-metatungstate (HMT) was applied in phasing the structure of death receptor 6. Even though the HA cluster is bound in alternate partially occupied orientations and is located at a special position, its correct localization and orientation could be determined at resolutions as low as 4.9 Å. The broad applicability of this approach was demonstrated for five different derivative crystals that included the compounds tantalum tetradeca­bromide and trisodium phosphotungstate in addition to HMT. The correct placement of the HA cluster depends on the length of the intramolecular vectors chosen for MR, such that both a larger cluster size and the optimal choice of the wavelength used for anomalous data collection strongly affect the outcome. PMID:23385464

Micro-structural evolution and biomineralization behavior of carbon nanofiber/bioactive glass composites induced by precursor aging time.

PubMed

Jia, Xiaolong; Tang, Tianhong; Cheng, Dan; Zhang, Cuihua; Zhang, Ran; Cai, Qing; Yang, Xiaoping

2015-12-01

Bioactive glass (BG)-containing carbon nanofibers (CNFs) are promising orthopaedic biomaterials. Herein, CNF composites were produced from electrospinning of polyacrylonitrile (PAN)/BG sol-gel precursor solution, followed by carbonization. Choosing 58S-type BG (mol%: 58.0% SiO2-26.3% CaO-15.7% P2O5) as the model, micro-structural evolution of CNF/BG composites was systematically evaluated in relating to aging times of BG precursor solution. With aging time prolonging, BG precursors underwent morphological changes from small sol clusters with loosely and randomly branched structure to highly crosslinked Si-network structure, showing continuous increase in solution viscosity. BG precursor solution with low viscosity could mix well with PAN solution, resulting in CNF composite with homogeneously distributed BG component. Whereas, BG precursor gel with densely crosslinked Si-network structure led to uneven distribution of BG component along final CNFs due to its significant phase separation from PAN component. Meanwhile, BG nanoparticles in CNFs demonstrated micro-structural evolution that they transited from weak to strong crystal state along with longer aging time. Biomineralization in simulated body fluid and in vitro osteoblasts proliferation were then applied to determine the bioactivity of CNF/BG composites. CNF/BG composites prepared from shorter aging time could induce both faster apatite deposition and cell proliferation rate. It was suggested weakly crystallized BG nanoparticles along CNFs dissolved fast and was able to provide numerous nucleation sites for apatite deposition, which also favored the proliferation of osteoblasts cells. Aging time could thus be a useful tool to regulate the biological features of CNF/BG composites. Copyright © 2015 Elsevier B.V. All rights reserved.

Syntheses, crystal structures and magnetic properties of complexes based on [Ni(L-L)3]2+ complex cations with dimethylderivatives of 2,2‧-bipyridine and TCNQ

NASA Astrophysics Data System (ADS)

Černák, Juraj; Hegedüs, Michal; Váhovská, Lucia; Kuchár, Juraj; Šoltésová, Daniela; Čižmár, Erik; Feher, Alexander; Falvello, L. R.

2018-03-01

From the aqueous-methanolic systems Ni(NO3)2 - LiTCNQ - 5,5‧-dmbpy and Ni(NO3)2 - LiTCNQ - 4,4‧-dmbpy three novel complexes [Ni(5,5‧-dmbpy)3](TCNQ)2 (1), [Ni(4,4‧-dmbpy)3](TCNQ)2 (2) and [Ni(4,4‧-dmbpy)3]2(TCNQ-TCNQ)(TCNQ)2•0.60H2O (3), were isolated in single crystal form. The new compounds were identified using chemical analyses and IR spectroscopy. Single crystal studies of all samples corroborated their compositions and have shown that their ionic structures contain the complex cations [Ni(5,5‧-dmbpy)]2+ (1) or [Ni(4,4‧-dmbpy)]2+ (2 and 3). The anionic parts of the respective crystal structures 1-3 are formed by TCNQṡ- anion-radicals and in 3 also by a σ-dimerized dianion (TCNQ-TCNQ)2- with a C-C distance of 1.663(5) Å. The supramolecular structures are governed by weak hydrogen bonding interactions. The variable-temperature (2-300 K) magnetic studies of 1 and 3 confirmed the presence of magnetically active Ni(II) atoms with S = 1 and TCNQṡ- anion-radicals with S = 1/2 while the (TCNQ-TCNQ)2- dianion is magnetically silent. The magnetic behavior was described by a complex magnetic model assuming strong antiferromagnetic interactions between some TCNQṡ- anion-radicals.

A new series of mixed oxalates MM'(C 2O 4) 3(H 2O) 3· nH 2O (M = Cd, Hg, Pb; M' = Zr, Hf) based on eight-fold coordinated metals: Synthesis, crystal structure from single-crystal and powder diffraction data and thermal behaviour

NASA Astrophysics Data System (ADS)

Gavilan, Elisabeth; Audebrand, Nathalie; Jeanneau, Erwann

2007-11-01

A new series of mixed oxalates MM'(C 2O 4) 3(H 2O) 3· nH 2O (M = Cd, Hg, Pb; M' = Zr, Hf) has been prepared. The crystal structures have been solved from single-crystal and powder diffraction data. The isotypical compounds crystallise with space group P2 1/ c (No. 14). The structures consist of honeycomb layers formed by eight-fold coordinated metals, in a distorted square-based antiprismatic conformation, connected together via oxalates which act as bidentate ligands and also as monodentate in a less-common μ3-bridging mode. Sheets are built from two shifted honeycomb layers and linked to each other through a hydrogen network. The resulting frameworks of the series display a compact two-dimensional arrangement of polyhedra MO 8 and M'O 8. Weakly-bonded water molecules are located between and within the sheets. Comparisons with the 3D open-framework structures of related metal oxalates are made. The dehydration processes occur in three or four steps. The final products are MO, M'O 2 and PbZrO 3 resulting from the sublimation of PbO in air. The size of PbZrO 3 crystallites, which are on average isotropic, has been evaluated to be 1055 Å from line-broadening analysis.

Commensurate Superstructure of the {Cu(NO3)(H2O)}(HTae)(Bpy) Coordination Polymer: An Example of 2D Hydrogen-Bonding Networks as Magnetic Exchange Pathway.

PubMed

Fernández de Luis, Roberto; Larrea, Edurne S; Orive, Joseba; Lezama, Luis; Arriortua, María I

2016-11-21

The average and commensurate superstructures of the one-dimensional coordination polymer {Cu(NO 3 )(H 2 O)}(HTae)(Bpy) (H 2 Tae = 1,1,2,2-tetraacetylethane, Bpy = 4,4'-bipyridine) were determined by single-crystal X-ray diffraction, and the possible symmetry relations between the space group of the average structure and the superstructure were checked. The crystal structure consists in parallel and oblique {Cu(HTae)(Bpy)} zigzag metal-organic chains stacked along the [100] crystallographic direction. The origin of the fivefold c axis in the commensurate superstructure is ascribed to a commensurate modulation of the coordination environment of the copper atoms. The commensurately ordered nitrate groups and coordinated water molecules establish a two-dimensional hydrogen-bonding network. Moreover, the crystal structure shows a commensurate to incommensurate transition at room temperature. The release of the coordination water molecules destabilizes the crystal framework, and the compound shows an irreversible structure transformation above 100 °C. Despite the loss of crystallinity, the spectroscopic studies indicate that the main building blocks of the crystal framework are retained after the transformation. The hydrogen-bonding network not only plays a crucial role stabilizing the crystal structure but also is an important pathway for magnetic exchange transmission. In fact, the magnetic susceptibility curves indicate that after the loss of coordinated water molecules, and hence the collapse of the hydrogen-bonding network, the weak anti-ferromagnetic coupling observed in the initial compound is broken. The electron paramagnetic resonance spectra are the consequence of the average signals from Cu(II) with different orientations, indicating that the magnetic coupling is effective between them. In fact, X- and Q-band data are reflecting different situations; the X-band spectra show the characteristics of an exchange g-tensor, while the Q-band signals are coming from both the exchange and the molecular g-tensors.

Crystal structure of 2-benzoyl­amino-N′-(4-hy­droxy­benzyl­idene)-3-(thio­phen-2-yl)prop-2-eno­hydrazide

PubMed Central

Subbulakshmi, Karanth N.; Narayana, Badiadka; Yathirajan, Hemmige S.; Jasinski, Jerry P.; Rathore, Ravindranath S.; Glidewell, Christopher

2016-01-01

In the title compound, C21H17N3O3S, the non-H atoms, apart from those in the benzoyl group, are almost coplanar (r.m.s. deviation = 0.049 Å) and the benzoyl group is almost orthogonal to the plane of the rest of the mol­ecule [dihedral angle = 80.34 (6)°]. In the crystal, a combination of N—H⋯O and asymmetric bifurcated O—H⋯(N,O) hydrogen bonds link the mol­ecules into a three-dimensional network. Weak C—H⋯O inter­actions are also observed. PMID:27536390

Spin-glass polyamorphism induced by a magnetic field in LaMnO3 single crystal

NASA Astrophysics Data System (ADS)

Eremenko, V. V.; Sirenko, V. A.; Baran, A.; Čižmár, E.; Feher, A.

2018-05-01

We present experimental evidence of field-driven transition in spin-glass state, similar to pressure-induced transition between amorphous phases in structural and metallic glasses, attributed to the polyamorphism phenomena. Cusp in temperature dependences of ac magnetic susceptibility of weakly disordered LaMnO3 single crystal is registered below the temperature of magnetic ordering. Frequency dependence of the cusp temperature proves its spin-glass origin. The transition induced by a magnetic field in spin-glass state, is manifested by peculiarity in dependence of cusp temperature on applied magnetic field. Field dependent maximum of heat capacity is observed in the same magnetic field and temperature range.

Enhanced light extraction of plastic scintillator using large-area photonic crystal structures fabricated by hot embossing.

PubMed

Chen, Xueye; Liu, Bo; Wu, Qiang; Zhu, Zhichao; Zhu, Jingtao; Gu, Mu; Chen, Hong; Liu, Jinliang; Chen, Liang; Ouyang, Xiaoping

2018-04-30

Plastic scintillators are widely used in various radiation measurement systems. However, detection efficiency and signal-to-noise are limited due to the total internal reflection, especially for weak signal detection situations. In the present investigation, large-area photonic crystals consisting of an array of periodic truncated cone holes were prepared based on hot embossing technology aiming at coupling with the surface of plastic scintillator to improve the light extraction efficiency and directionality control. The experimental results show that a maximum enhancement of 64% at 25° emergence angle along Γ-M orientation and a maximum enhancement of 58% at 20° emergence angle along Γ-K orientation were obtained. The proposed fabrication method of photonic crystal scintillator can avoid complicated pattern transfer processes used in most traditional methods, leading to a simple, economical method for large-area preparation. The photonic crystal scintillator demonstrated in this work is of great value for practical applications of nuclear radiation detection.

The direct-to-indirect band gap crossover in two-dimensional van der Waals Indium Selenide crystals

PubMed Central

Mudd, G. W.; Molas, M. R.; Chen, X.; Zólyomi, V.; Nogajewski, K.; Kudrynskyi, Z. R.; Kovalyuk, Z. D.; Yusa, G.; Makarovsky, O.; Eaves, L.; Potemski, M.; Fal’ko, V. I.; Patanè, A.

2016-01-01

The electronic band structure of van der Waals (vdW) layered crystals has properties that depend on the composition, thickness and stacking of the component layers. Here we use density functional theory and high field magneto-optics to investigate the metal chalcogenide InSe, a recent addition to the family of vdW layered crystals, which transforms from a direct to an indirect band gap semiconductor as the number of layers is reduced. We investigate this direct-to-indirect bandgap crossover, demonstrate a highly tuneable optical response from the near infrared to the visible spectrum with decreasing layer thickness down to 2 layers, and report quantum dot-like optical emissions distributed over a wide range of energy. Our analysis also indicates that electron and exciton effective masses are weakly dependent on the layer thickness and are significantly smaller than in other vdW crystals. These properties are unprecedented within the large family of vdW crystals and demonstrate the potential of InSe for electronic and photonic technologies. PMID:28008964

The direct-to-indirect band gap crossover in two-dimensional van der Waals Indium Selenide crystals.

PubMed

Mudd, G W; Molas, M R; Chen, X; Zólyomi, V; Nogajewski, K; Kudrynskyi, Z R; Kovalyuk, Z D; Yusa, G; Makarovsky, O; Eaves, L; Potemski, M; Fal'ko, V I; Patanè, A

2016-12-23

The electronic band structure of van der Waals (vdW) layered crystals has properties that depend on the composition, thickness and stacking of the component layers. Here we use density functional theory and high field magneto-optics to investigate the metal chalcogenide InSe, a recent addition to the family of vdW layered crystals, which transforms from a direct to an indirect band gap semiconductor as the number of layers is reduced. We investigate this direct-to-indirect bandgap crossover, demonstrate a highly tuneable optical response from the near infrared to the visible spectrum with decreasing layer thickness down to 2 layers, and report quantum dot-like optical emissions distributed over a wide range of energy. Our analysis also indicates that electron and exciton effective masses are weakly dependent on the layer thickness and are significantly smaller than in other vdW crystals. These properties are unprecedented within the large family of vdW crystals and demonstrate the potential of InSe for electronic and photonic technologies.

Quantitative analysis of weak interactions by Lattice energy calculation, Hirshfeld surface and DFT studies of sulfamonomethoxine

NASA Astrophysics Data System (ADS)

Patel, Kinjal D.; Patel, Urmila H.

2017-01-01

Sulfamonomethoxine, 4-Amino-N-(6-methoxy-4-pyrimidinyl) benzenesulfonamide (C11H12N4O3S), is investigated by single crystal X-ray diffraction technique. Pair of N-H⋯N and C-H⋯O intermolecular interactions along with π···π interaction are responsible for the stability of the molecular packing of the structure. In order to understand the nature of the interactions and their quantitative contributions towards the crystal packing, the 3D Hirshfeld surface and 2D fingerprint plot analysis are carried out. PIXEL calculations are performed to determine the lattice energies correspond to intermolecular interactions in the crystal structure. Ab initio quantum chemical calculations of sulfamonomethoxine (SMM) have been performed by B3LYP method, using 6-31G** basis set with the help of Schrodinger software. The computed geometrical parameters are in good agreement with the experimental data. The Mulliken charge distribution, calculated using B3LYP method to confirm the presence of electron acceptor and electron donor atoms, responsible for intermolecular hydrogen bond interactions hence the molecular stability.

Crystal and molecular structure of N-(4-nitrophenyl)-β-alanine—Its vibrational spectra and theoretical calculations

NASA Astrophysics Data System (ADS)

Marchewka, M. K.; Drozd, M.; Janczak, J.

2011-08-01

The N-(4-nitrophenyl)-β-alanine in crystalline form directly by the addition of 4-nitroaniline to the acrylic acid in aqueous solution has been obtained. The title β-alanine derivative crystallizes in the P2 1/ c space group of monoclinic system with four molecules per unit cell. The X-ray geometry of β-alanine derivative molecule has been compared with those obtained by molecular orbital calculations corresponding to the gas phase. In the crystal the molecules related by an inversion center interact via symmetrically equivalent O-H⋯O hydrogen bonds with O⋯O distance of 2.656(2) Å forming a dimeric structure. The dimers of β-alanine derivative weakly interact via N-H⋯O hydrogen bonds between the H atom of β-amine groups and one of O atom of nitro groups. The room temperature powder vibrational (infrared and Raman) measurements are in accordance with the X-ray analysis. In aqueous solution of 4-nitroaniline and acrylic acid, the double C dbnd C bond of vinyl group of acrylic acid breaks as result of 4-nitroaniline addition.

Room-temperature serial crystallography at synchrotron X-ray sources using slowly flowing free-standing high-viscosity microstreams.

PubMed

Botha, Sabine; Nass, Karol; Barends, Thomas R M; Kabsch, Wolfgang; Latz, Beatrice; Dworkowski, Florian; Foucar, Lutz; Panepucci, Ezequiel; Wang, Meitian; Shoeman, Robert L; Schlichting, Ilme; Doak, R Bruce

2015-02-01

Recent advances in synchrotron sources, beamline optics and detectors are driving a renaissance in room-temperature data collection. The underlying impetus is the recognition that conformational differences are observed in functionally important regions of structures determined using crystals kept at ambient as opposed to cryogenic temperature during data collection. In addition, room-temperature measurements enable time-resolved studies and eliminate the need to find suitable cryoprotectants. Since radiation damage limits the high-resolution data that can be obtained from a single crystal, especially at room temperature, data are typically collected in a serial fashion using a number of crystals to spread the total dose over the entire ensemble. Several approaches have been developed over the years to efficiently exchange crystals for room-temperature data collection. These include in situ collection in trays, chips and capillary mounts. Here, the use of a slowly flowing microscopic stream for crystal delivery is demonstrated, resulting in extremely high-throughput delivery of crystals into the X-ray beam. This free-stream technology, which was originally developed for serial femtosecond crystallography at X-ray free-electron lasers, is here adapted to serial crystallography at synchrotrons. By embedding the crystals in a high-viscosity carrier stream, high-resolution room-temperature studies can be conducted at atmospheric pressure using the unattenuated X-ray beam, thus permitting the analysis of small or weakly scattering crystals. The high-viscosity extrusion injector is described, as is its use to collect high-resolution serial data from native and heavy-atom-derivatized lysozyme crystals at the Swiss Light Source using less than half a milligram of protein crystals. The room-temperature serial data allow de novo structure determination. The crystal size used in this proof-of-principle experiment was dictated by the available flux density. However, upcoming developments in beamline optics, detectors and synchrotron sources will enable the use of true microcrystals. This high-throughput, high-dose-rate methodology provides a new route to investigating the structure and dynamics of macromolecules at ambient temperature.

Resolution of 2-chloromandelic acid with (R)-(+)-N-benzyl-1-phenylethylamine: chiral discrimination mechanism.

PubMed

Peng, Yangfeng; He, Quan; Rohani, Sohrab; Jenkins, Hilary

2012-05-01

During the resolution of 2-chloromandelic acid with (R)-(+)-N-benzyl-1-phenylethylamine, the crystals of the less soluble salt were grown, and their structure were determined and presented. The chiral discrimination mechanism was investigated by examining the weak intermolecular interactions (such as hydrogen bond, CH/π, and van der Waals interactions) and molecular packing mode in crystal structure of the less soluble diastereomeric salt. A one-dimensional double-chain hydrogen-bonding network and a "lock-and-key" supramolecular packing mode are disclosed. The investigation demonstrates that hydrophobic layers with corrugated surfaces can fit into the grooves of one another to realize a compact packing, when the molecular structure of resolving agent is much larger than that of the racemate. This "lock-and-key" assembly is recognized to be another characteristic of molecular packing contributing to the chiral discrimination, in addition to the well-known sandwich-like packing by hydrophobic layers with planar boundary surfaces. Copyright © 2012 Wiley Periodicals, Inc.

Correlations Between Structural and Magnetic Properties of Co2 FeSi Heusler-Alloy Thin Films

NASA Astrophysics Data System (ADS)

Zhu, Weihua; Wu, Di; Zhao, Bingcheng; Zhu, Zhendong; Yang, Xiaodi; Zhang, Zongzhi; Jin, Q. Y.

2017-09-01

The structural and magnetic properties are the most important parameters for practical applications of Co-based Heusler alloys. The correlations between the crystallization degree, chemical order, magnetic coercivity, saturation magnetization (MS ), and in-plane magnetic anisotropies are systematically investigated for Co2FeSi (CFS) films fabricated at different temperatures (TS ). XRD shows that the CFS layer changes progressively from a disordered crystal structure into a chemically disordered A 2 structure and further into a chemically ordered B 2 and even L 21 structures when increasing TS up to 480 °C . Meanwhile, the static angular remanence magnetization curves show a clear transition of magnetic anisotropy from twofold to fourfold symmetry, due to the competition effect between the uniaxial anisotropy field HU and biaxial anisotropy field HB . The HU value is found to be weakly dependent on TS , while HB shows a continuous enhancement at TS>300 °C , implying that the enhancement of the L 21 ordering degree would not weaken the biaxial anisotropy. The varying trend of HB is similar to MS , which can be respectively attributed to the improved crystal structure and chemical order. The anisotropic fields and their variation behaviors determined by a vibrating sample magnetometer are highly consistent with the results by a time-resolved magneto-optical Kerr effect study. Our findings provide a better understanding of the structural ordering and magnetic anisotropy, which will be helpful for designing advanced spintronic devices.

Synthesis, crystal structure, and properties of KSbO{sub 3}-type Bi{sub 3}Mn{sub 1.9}Te{sub 1.1}O{sub 11}

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li Manrong; Retuerto, Maria; Bok Go, Yong

2013-01-15

Single crystals of Bi{sub 3}Mn{sub 1.9}Te{sub 1.1}O{sub 11} were prepared from NaCl+KCl flux. This compound adopts KSbO{sub 3}-type crystal structure as evidenced by electron and single crystal X-ray diffraction analysis. The three-dimensional channel structure is formed by corner-sharing octahedral (Mn{sub 0.63}Te{sub 0.37}){sub 2}O{sub 10} dimers and two identical (Bi1){sub 4}(Bi2){sub 2} interpenetrating lattices. The intra-dimer Mn/Te-Mn/Te distances in Bi{sub 3}Mn{sub 1.9}Te{sub 1.1}O{sub 11} are short and are consistent with weak metal-metal interactions. The mixed oxidation state of manganese and the edge-sharing octahedral features are confirmed by X-ray near edge absorption spectroscopy measurements, which indicate Bi{sub 3}(Mn{sup III}{sub 1.1}Mn{sup IV}{sub 0.8})Te{supmore » VI}{sub 1.1}O{sub 11} with 57.7% Mn{sup 3+} and 42.3% Mn{sup 4+}. The partial substitution of Te for Mn perturbs long-range magnetic interactions, thereby destroying the ferromagnetic ordering found in Bi{sub 3}Mn{sub 3}O{sub 11} (T{sub C}=150 K). - Graphical abstract: Single crystal of Bi{sub 3}Mn{sub 1.9}Te{sub 1.1}O{sub 11} was grown from NaCl+KCl binary flux, suggesting that the high pressure Bi{sub 3}Mn{sub 3}O{sub 11} phase can be stabilized by partial substitution of Mn by Te at ambient pressure. Bi{sub 3}Mn{sub 1.9}Te{sub 1.1}O{sub 11} adopts a typical three dimensional KSbO{sub 3}-type crystal structure with three interpenetrating lattices and weak intra-dimmer metal-metal interaction caused by the d electrons of Mn. The edge-shared (Mn{sub 0.63}Te{sub 0.37}){sub 2}O{sub 10} octahedral dimer and mixed oxidation state of manganese (Bi{sub 3}(Mn{sup III}{sub 1.1}Mn{sup IV}{sub 0.8})Te{sup VI}{sub 1.1}O{sub 11} with 57.7% Mn{sup 3+} and 42.3% Mn{sup 4+}) features were evidenced by X-ray absorption near edge spectroscopy. Compared with Bi{sub 3}Mn{sub 3}O{sub 11}, the Te substituted Bi{sub 3}Mn{sub 1.9}Te{sub 1.1}O{sub 11} relaxes the crystal structure, but destroys the long-range magnetic ordering and gives short-range magnetic ordering below 5 K. Highlights: Black-Right-Pointing-Pointer High pressure Bi{sub 3}Mn{sub 3}O{sub 11} is stabilized by partial Te substitution at ambient pressure. Black-Right-Pointing-Pointer New KSbO{sub 3}-type Bi{sub 3}Mn{sub 1.9}Te{sub 1.1}O{sub 11} single crystal was grown from binary flux. Black-Right-Pointing-Pointer The presence of mixed oxidation state of manganese is evidenced by XANES study. Black-Right-Pointing-Pointer The Te-substitution destroys the long-range magnetic ordering and relaxes the structure.« less

Crystal structures, Hirshfeld surface analysis, thermal behavior and dielectric properties of a new organic-inorganic hybrid [C6H10(NH3)2]Cu2Cl8

NASA Astrophysics Data System (ADS)

Salah, Najet; Hamdi, Besma; Bouzidia, Nabaa; Salah, Abdelhamid Ben

2017-12-01

A novel organic-inorganic hybrid sample [C6H10(NH3)2]Cu2Cl8 has been prepared under mild hydrothermal conditions and characterized by single crystal X-ray diffraction, Hirshfeld surface analysis, FT-IR,NMR and UV-Vis spectroscopies, differential scanning calorimetric and dielectric measurement. It is crystallized in the monoclinic system with P21/c space group. The cohesion and stabilization of the structure are provided by the hydrogen bond interactions, (Nsbnd H⋯Cl and Csbnd H⋯Cl), between [C6H10(NH3)2]2+ cation and [Cu2Cl8]2- anion. The Hirschfeld surface analysis has been performed to explore the behavior of these weak interactions. The presence of different functional groups and the nature of their vibrations were identified by FT-IR and Solid state NMR. The thermal study revealed that this compound undergoes two structural phase transitions around 353 and 376 K. Electrical measurements of our compounds have been investigated using complex impedance spectroscopy (CIS) in the frequency and temperature range 331-399 K and 200 Hz-5 MHz, respectively. The AC conductivity is explained using the correlated barrier hopping model (CBH) conduction mechanism. The nature of DC conductivity variation suggests Arrhenius type of electrical conductivity. A relationship between crystal structure and ionic conductivity was established and discussed. Finally, the real and imaginary parts of the permittivity constant are analyzed with the Cole-Cole formalism and the optical spectra indicate that the compound has a direct band gap (3.14 eV) due to direct transition. The wide band gap is due to low defect concentration in the grown crystal, which is more useful for the laser/optical applications.

Antiferromagnetism in the van der Waals layered spin-lozenge semiconductor CrTe 3

DOE PAGES

McGuire, Michael A.; Garlea, V. Ovidiu; KC, Santosh; ...

2017-04-14

We have investigated the crystallographic, magnetic, and transport properties of the van der Waals bonded, layered compound CrTe 3 on single-crystal and polycrystalline materials. Furthermore, the crystal structure contains layers made up of lozenge-shaped Cr 4 tetramers. Electrical resistivity measurements show the crystals to be semiconducting, with a temperature dependence consistent with a band gap of 0.3 eV. The magnetic susceptibility exhibits a broad maximum near 300 K characteristic of low dimensional magnetic systems. Weak anomalies are observed in the susceptibility and heat capacity near 55 K, and single-crystal neutron diffraction reveals the onset of long-range antiferromagnetic order at thismore » temperature. Strongly dispersive spin waves are observed in the ordered state. Significant magnetoelastic coupling is indicated by the anomalous temperature dependence of the lattice parameters and is evident in structural optimization in van der Waals density functional theory calculations for different magnetic configurations. The cleavability of the compound is apparent from its handling and is confirmed by first-principles calculations, which predict a cleavage energy 0.5 J / m 2 , similar to graphite. Based on our results, CrTe 3 is identified as a promising compound for studies of low dimensional magnetism in bulk crystals as well as magnetic order in monolayer materials and van der Waals heterostructures.« less

Antiferromagnetism in the van der Waals layered spin-lozenge semiconductor CrTe 3

DOE Office of Scientific and Technical Information (OSTI.GOV)

McGuire, Michael A.; Garlea, V. Ovidiu; KC, Santosh

We have investigated the crystallographic, magnetic, and transport properties of the van der Waals bonded, layered compound CrTe 3 on single-crystal and polycrystalline materials. Furthermore, the crystal structure contains layers made up of lozenge-shaped Cr 4 tetramers. Electrical resistivity measurements show the crystals to be semiconducting, with a temperature dependence consistent with a band gap of 0.3 eV. The magnetic susceptibility exhibits a broad maximum near 300 K characteristic of low dimensional magnetic systems. Weak anomalies are observed in the susceptibility and heat capacity near 55 K, and single-crystal neutron diffraction reveals the onset of long-range antiferromagnetic order at thismore » temperature. Strongly dispersive spin waves are observed in the ordered state. Significant magnetoelastic coupling is indicated by the anomalous temperature dependence of the lattice parameters and is evident in structural optimization in van der Waals density functional theory calculations for different magnetic configurations. The cleavability of the compound is apparent from its handling and is confirmed by first-principles calculations, which predict a cleavage energy 0.5 J / m 2 , similar to graphite. Based on our results, CrTe 3 is identified as a promising compound for studies of low dimensional magnetism in bulk crystals as well as magnetic order in monolayer materials and van der Waals heterostructures.« less

Crystal structure of 1,3-bis­(1H-benzotriazol-1-yl­meth­yl)benzene

PubMed Central

Macías, Mario A.; Nuñez-Dallos, Nelson; Hurtado, John; Suescun, Leopoldo

2016-01-01

The mol­ecular structure of the title compound, C20H16N6, contains two benzotriazole units bonded to a benzene nucleus in a meta configuration, forming dihedral angles of 88.74 (11) and 85.83 (10)° with the central aromatic ring and 57.08 (9)° with each other. The three-dimensional structure is controlled mainly by weak C—H⋯N and C—H⋯π inter­actions. The mol­ecules are connected in inversion-related pairs, forming the slabs of infinite chains that run along the [-110] and [110] directions. PMID:27308049

Ternary metal-rich sulfide with a layered structure

DOEpatents

Franzen, Hugo F.; Yao, Xiaoqiang

1993-08-17

A ternary Nb-Ta-S compound is provided having the atomic formula, Nb.sub.1.72 Ta.sub.3.28 S.sub.2, and exhibiting a layered structure in the sequence S-M3-M2-M1-M2-M3-S wherein S represents sulfur layers and M1, M2, and M3 represent Nb/Ta mixed metal layers. This sequence generates seven sheets stacked along the [001] direction of an approximate body centered cubic crystal structure with relatively weak sulfur-to-sulfur van der Waals type interactions between adjacent sulfur sheets and metal-to-metal bonding within and between adjacent mixed metal sheets.

In situ SAXS study on cationic and non-ionic surfactant liquid crystals using synchrotron radiation.

PubMed

Fritscher, C; Hüsing, N; Bernstorff, S; Brandhuber, D; Koch, T; Seidler, S; Lichtenegger, H C

2005-11-01

In situ synchrotron small-angle X-ray scattering was used to investigate various surfactant/water systems with hexagonal and lamellar structures regarding their structural behaviour upon heating and cooling. Measurements of the non-ionic surfactant Triton X-45 (polyethylene glycol 4-tert-octylphenyl ether) at different surfactant concentrations show an alignment of the lamellar liquid-crystalline structure close to the wall of the glass capillaries and also a decrease in d-spacing following subsequent heating/cooling cycles. Additionally, samples were subjected to a weak magnetic field (0.3-0.7 T) during heating and cooling, but no influence of the magnetic field was observed.

Spectroscopic study of uracil, 1-methyluracil and 1-methyl-4-thiouracil: Hydrogen bond interactions in crystals and ab-initio molecular dynamics.

PubMed

Brela, Mateusz Z; Boczar, Marek; Malec, Leszek M; Wójcik, Marek J; Nakajima, Takahito

2018-05-15

Hydrogen bond networks in uracil, 1-methyluracil and 1-methyl-4-thiouracil were studied by ab initio molecular dynamics as well as analysis of the orbital interactions. The power spectra calculated by ab initio molecular dynamics for atoms involved in hydrogen bonds were analyzed. We calculated spectra by using anharmonic approximation based on the autocorrelation function of the atom positions obtained from the Born-Oppenheimer simulations. Our results show the differences between hydrogen bond networks in uracil and its methylated derivatives. The studied methylated derivatives, 1-methyluracil as well as 1-methyl-4-thiouracil, form dimeric structures in the crystal phase, while uracil does not form that kind of structures. The presence of sulfur atom instead oxygen atom reflects weakness of the hydrogen bonds that build dimers. Copyright © 2018 Elsevier B.V. All rights reserved.

Crystal structures of two bis-(iodo-meth-yl)benzene derivatives: similarities and differences in the crystal packing.

PubMed

McAdam, C John; Hanton, Lyall R; Moratti, Stephen C; Simpson, Jim

2015-12-01

The isomeric derivatives 1,2-bis-(iodo-meth-yl)benzene, (I), and 1,3-bis-(iodo-meth-yl)benzene (II), both C8H8I2, were prepared by metathesis from their di-bromo analogues. The ortho-derivative, (I), lies about a crystallographic twofold axis that bis-ects the C-C bond between the two iodo-methyl substituents. The packing in (I) relies solely on C-H⋯I hydrogen bonds supported by weak parallel slipped π-π stacking inter-actions [inter-centroid distance = 4.0569 (11) Å, inter-planar distance = 3.3789 (8) Å and slippage = 2.245 Å]. While C-H⋯I hydrogen bonds are also found in the packing of (II), type II, I⋯I halogen bonds [I⋯I = 3.8662 (2) Å] and C-H⋯π contacts feature prominently in stabilizing the three-dimensional structure.

A Nanoindentation Study of the Plastic Deformation and Fracture Mechanisms in Single-Crystalline CaFe2As2

NASA Astrophysics Data System (ADS)

Frawley, Keara G.; Bakst, Ian; Sypek, John T.; Vijayan, Sriram; Weinberger, Christopher R.; Canfield, Paul C.; Aindow, Mark; Lee, Seok-Woo

2018-04-01

The plastic deformation and fracture mechanisms in single-crystalline CaFe2As2 has been studied using nanoindentation and density functional theory simulations. CaFe2As2 single crystals were grown in a Sn-flux, resulting in homogeneous and nearly defect-free crystals. Nanoindentation along the [001] direction produces strain bursts, radial cracking, and lateral cracking. Ideal cleavage simulations along the [001] and [100] directions using density functional theory calculations revealed that cleavage along the [001] direction requires a much lower stress than cleavage along the [100] direction. This strong anisotropy of cleavage strength implies that CaFe2As2 has an atomic-scale layered structure, which typically exhibits lateral cracking during nanoindentation. This special layered structure results from weak atomic bonding between the (001) Ca and Fe2As2 layers.

A Nanoindentation Study of the Plastic Deformation and Fracture Mechanisms in Single-Crystalline CaFe 2As 2

DOE PAGES

Frawley, Keara G.; Bakst, Ian; Sypek, John T.; ...

2018-04-10

In this paper, the plastic deformation and fracture mechanisms in single-crystalline CaFe 2As 2 has been studied using nanoindentation and density functional theory simulations. CaFe 2As 2 single crystals were grown in a Sn-flux, resulting in homogeneous and nearly defect-free crystals. Nanoindentation along the [001] direction produces strain bursts, radial cracking, and lateral cracking. Ideal cleavage simulations along the [001] and [100] directions using density functional theory calculations revealed that cleavage along the [001] direction requires a much lower stress than cleavage along the [100] direction. This strong anisotropy of cleavage strength implies that CaFe 2As 2 has an atomic-scalemore » layered structure, which typically exhibits lateral cracking during nanoindentation. This special layered structure results from weak atomic bonding between the (001) Ca and Fe 2As 2 layers.« less

A Nanoindentation Study of the Plastic Deformation and Fracture Mechanisms in Single-Crystalline CaFe 2As 2

DOE Office of Scientific and Technical Information (OSTI.GOV)

Frawley, Keara G.; Bakst, Ian; Sypek, John T.

In this paper, the plastic deformation and fracture mechanisms in single-crystalline CaFe 2As 2 has been studied using nanoindentation and density functional theory simulations. CaFe 2As 2 single crystals were grown in a Sn-flux, resulting in homogeneous and nearly defect-free crystals. Nanoindentation along the [001] direction produces strain bursts, radial cracking, and lateral cracking. Ideal cleavage simulations along the [001] and [100] directions using density functional theory calculations revealed that cleavage along the [001] direction requires a much lower stress than cleavage along the [100] direction. This strong anisotropy of cleavage strength implies that CaFe 2As 2 has an atomic-scalemore » layered structure, which typically exhibits lateral cracking during nanoindentation. This special layered structure results from weak atomic bonding between the (001) Ca and Fe 2As 2 layers.« less

Liquid crystal behavior induced assembling fabrication of conductive chiral MWCNTs@NCC nanopaper

NASA Astrophysics Data System (ADS)

Ren, Yumei; Wang, Tianjiao; Chen, Zhimin; Li, Jing; Tian, Qiuge; Yang, Hongxia; Xu, Qun

2016-11-01

The conductive chiral MWCNTs@NCC nanopapers obtained by the assembly of nanocrystalline cellulose liquid crystals (NCC LCs) host matrix along with one-dimensional (1-D) multi-walled carbon nanotubes (MWCNTs) have been studied in this work. Circular dichroism (CD) studies show strong signals stemming from the chiral nematic structure. Notably, the introduction of the MWCNTs has a pronounced effect on the chiral structure of the as-prepared nanopaper. Our experimental results indicate the multiple weak molecular interactions existing between MWCNTs and NCC are responsible for the effective dispersion and stabilization of MWCNTs. Moreover it also confirms the resulting nanopaper has an increased conductivity of 4.2 S/m at 1.96 wt% MWCNTs. So the co-assembly of the nanocomposite herein opens a gateway for preparing functional materials combining the photonic properties of the NCC LCs matrix with other building blocks that can supply other advantageous functions.

Crystal structure of N'-[(E)-(4-chloro-phen-yl)(phen-yl)methyl-idene]-4-methyl-benzene-sulfono-hydrazide.

PubMed

Balaji, J; Prabu, S; Xavier, J J F; Srinivasan, P

2015-01-01

The title compound, C20H17ClN2O2S, was obtained by a condensation reaction between 4-chloro-benzo-phenone and tosyl hydrazide. The plane of the methyl-substituted benzene ring forms dihedral angles of 20.12 (12) and 78.43 (13)° with those of the chlorine-substituted benzene ring and the benzene ring, respectively, with the last two rings forming a dihedral angle of 67.81 (13)°. The chlorine substituent was also found to be 0.868 (2):0.132 (2) disordered over these two rings. In the crystal, mol-ecules are linked through pairs of N-H⋯O hydrogen bonds, giving centrosymmetric cyclic dimers [graph set R 2 (2)(8)], which are linked by weak C-H⋯O and C-H⋯Cl inter-actions into a chain structure which extends along the a-axis direction.

Solid-state modeling of the terahertz spectrum of the high explosive HMX.

PubMed

Allis, Damian G; Prokhorova, Darya A; Korter, Timothy M

2006-02-09

The experimental solid-state terahertz (THz) spectrum (3-120 cm(-1)) of the beta-crystal form of the high explosive octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX) has been analyzed using solid-state density functional theory calculations. Various density functionals (both generalized gradient approximation and local density approximation) are compared in terms of their abilities to reproduce the experimentally observed solid-state structure and low-frequency vibrational motions. Good-to-excellent agreement between solid-state theory and experiment can be achieved in the THz region where isolated-molecule calculations fail to reproduce the observed spectral features, demonstrating a clear limitation of using isolated-molecule calculations for the assignment of THz frequency motions in molecular solids. The deficiency of isolated-molecule calculations is traced to modification of the molecular structure in the solid state through crystal packing effects and the formation of weak C-H...O hydrogen bonds.

Crystal structure of (1S,2S,2′R,3a′S,5R)-2′-[(5-bromo-1H-indol-3-yl)meth­yl]-2-isopropyl-5,5′-dimethyl­dihydro-2′H-spiro­[cyclo­hexane-1,6′-imidazo[1,5-b]isoxazol]-4′(5′H)-one

PubMed Central

Ghannay, Siwar; Brahmi, Jihed; Nasri, Soumaya; Aouadi, Kaïss; Jeanneau, Erwann; Msaddek, Moncef

2016-01-01

In the title compound, C24H32BrN3O2, the six-membered cyclo­hexane ring adopts a chair conformation and the isoxasolidine ring adopts a twisted conformation. The mol­ecule has five chiral centres and the absolute configuration has been determined in this analysis. The mol­ecular structure is stabilized by weak intra­molecular C—H⋯O and C—H⋯N contacts. In the crystal, mol­ecules are linked by N—H⋯N and C—H⋯O hydrogen bonds, forming undulating sheets parallel to the bc plane. PMID:27536387

Leucocontextins A-R, lanostane-type triterpenoids from Ganoderma leucocontextum.

PubMed

Zhao, Zhen-Zhu; Chen, He-Ping; Li, Zheng-Hui; Dong, Ze-Jun; Bai, Xue; Zhou, Zhong-Yu; Feng, Tao; Liu, Ji-Kai

2016-03-01

Eighteen new lanostane-type triterpenoids, namely leucocontextins A-R (1-18) were isolated from the fruiting bodies of Ganoderma leucocontextum. Their structures were established by 1D and 2D NMR data in conjunction with HRESIMS/HREIMS, X-ray single crystal diffraction analysis. Compound 18 exhibited weak cytotoxicity against K562 and MCF-7 cell lines with IC50 of 20-30 μM. Copyright © 2015 Elsevier B.V. All rights reserved.

Propyl 3-oxo-2,3-dihydro-1,2-benzothia-zole-2-carboxyl-ate.

PubMed

Wang, Xiang-Hui; Yang, Jian-Xin; You, Cheng-Hang; Lin, Qiang

2011-09-01

The title compound, C(11)H(11)NO(3)S, was synthesized by the reaction of benzo[d]isothia-zol-3(2H)-one with propyl carbono-chloridate in toluene. The benzoisothiazolone ring system is approximately planar with a maximum deviation from the mean plane of 0.0226 (14) Å for the N atom. Weak inter-molecular C-H⋯O hydrogen bonding occurs in the crystal structure.

Synthesis and characterization of Fe-Ti-Sb intermetallic compounds: Discovery of a new Slater-Pauling phase

NASA Astrophysics Data System (ADS)

Naghibolashrafi, N.; Keshavarz, S.; Hegde, Vinay I.; Gupta, A.; Butler, W. H.; Romero, J.; Munira, K.; LeClair, P.; Mazumdar, D.; Ma, J.; Ghosh, A. W.; Wolverton, C.

2016-03-01

Compounds of Fe, Ti, and Sb were prepared using arc melting and vacuum annealing. Fe2TiSb , expected to be a full Heusler compound crystallizing in the L 21 structure, was shown by XRD and SEM analyses to be composed of weakly magnetic grains of nominal composition Fe1.5TiSb with iron-rich precipitates in the grain boundaries. FeTiSb, a composition consistent with the formation of a half-Heusler compound, also decomposed into Fe1.5TiSb grains with Ti-Sb rich precipitates and was weakly magnetic. The dominant Fe1.5TiSb phase appears to crystallize in a defective L 21 -like structure with iron vacancies. Based on this finding, a first-principles DFT-based binary cluster expansion of Fe and vacancies on the Fe sublattice of the L 21 structure was performed. Using the cluster expansion, we computationally scanned >103 configurations and predict a novel, stable, nonmagnetic semiconductor phase to be the zero-temperature ground state. This new structure is an ordered arrangement of Fe and vacancies, belonging to the space group R 3 m , with composition Fe1.5TiSb , i.e., between the full- and half-Heusler compositions. This phase can be visualized as alternate layers of L 21 phase Fe2TiSb and C 1b phase FeTiSb, with layering along the [111] direction of the original cubic phases. Our experimental results on annealed samples support this predicted ground-state composition, but further work is required to confirm that the R 3 m structure is the ground state.

Nature of the anomalies in the supercooled liquid state of the mW model of water.

PubMed

Holten, Vincent; Limmer, David T; Molinero, Valeria; Anisimov, Mikhail A

2013-05-07

The thermodynamic properties of the supercooled liquid state of the mW model of water show anomalous behavior. Like in real water, the heat capacity and compressibility sharply increase upon supercooling. One of the possible explanations of these anomalies, the existence of a second (liquid-liquid) critical point, is not supported by simulations for this model. In this work, we reproduce the anomalies of the mW model with two thermodynamic scenarios: one based on a non-ideal "mixture" with two different types of local order of the water molecules, and one based on weak crystallization theory. We show that both descriptions accurately reproduce the model's basic thermodynamic properties. However, the coupling constant required for the power laws implied by weak crystallization theory is too large relative to the regular backgrounds, contradicting assumptions of weak crystallization theory. Fluctuation corrections outside the scope of this work would be necessary to fit the forms predicted by weak crystallization theory. For the two-state approach, the direct computation of the low-density fraction of molecules in the mW model is in agreement with the prediction of the phenomenological equation of state. The non-ideality of the "mixture" of the two states never becomes strong enough to cause liquid-liquid phase separation, also in agreement with simulation results.

Nature of the anomalies in the supercooled liquid state of the mW model of water

NASA Astrophysics Data System (ADS)

Holten, Vincent; Limmer, David T.; Molinero, Valeria; Anisimov, Mikhail A.

2013-05-01

The thermodynamic properties of the supercooled liquid state of the mW model of water show anomalous behavior. Like in real water, the heat capacity and compressibility sharply increase upon supercooling. One of the possible explanations of these anomalies, the existence of a second (liquid-liquid) critical point, is not supported by simulations for this model. In this work, we reproduce the anomalies of the mW model with two thermodynamic scenarios: one based on a non-ideal "mixture" with two different types of local order of the water molecules, and one based on weak crystallization theory. We show that both descriptions accurately reproduce the model's basic thermodynamic properties. However, the coupling constant required for the power laws implied by weak crystallization theory is too large relative to the regular backgrounds, contradicting assumptions of weak crystallization theory. Fluctuation corrections outside the scope of this work would be necessary to fit the forms predicted by weak crystallization theory. For the two-state approach, the direct computation of the low-density fraction of molecules in the mW model is in agreement with the prediction of the phenomenological equation of state. The non-ideality of the "mixture" of the two states never becomes strong enough to cause liquid-liquid phase separation, also in agreement with simulation results.

Photoluminescence characteristics of ZnTe bulk crystal and ZnTe epilayer grown on GaAs substrate by MOVPE

NASA Astrophysics Data System (ADS)

Lü, Hai-Yan; Mu, Qi; Zhang, Lei; Lü, Yuan-Jie; Ji, Zi-Wu; Feng, Zhi-Hong; Xu, Xian-Gang; Guo, Qi-Xin

2015-12-01

Excitation power and temperature-dependent photoluminescence (PL) spectra of the ZnTe epilayer grown on (100) GaAs substrate and ZnTe bulk crystal are investigated. The measurement results show that both the structures are of good structural quality due to their sharp bound excitonic emissions and absence of the deep level structural defect-related emissions. Furthermore, in contrast to the ZnTe bulk crystal, although excitonic emissions for the ZnTe epilayer are somewhat weak, perhaps due to As atoms diffusing from the GaAs substrate into the ZnTe epilayer and/or because of the strain-induced degradation of the crystalline quality of the ZnTe epilayer, neither the donor-acceptor pair (DAP) nor conduction band-acceptor (e-A) emissions are observed in the ZnTe epilayer. This indicates that by further optimizing the growth process it is possible to obtain a high-crystalline quality ZnTe heteroepitaxial layer that is comparable to the ZnTe bulk crystal. Project supported by the Specialized Research Fund for the Doctoral Program of Higher Education of China (Grant No. 20120131110006), the Key Science and Technology Program of Shandong Province, China (Grant No. 2013GGX10221), the Key Laboratory of Functional Crystal Materials and Device (Shandong University, Ministry of Education), China (Grant No. JG1401), the National Natural Science Foundation of China (Grant No. 61306113), the Major Research Plan of the National Natural Science Foundation of China (Grant No. 91433112), and the Partnership Project for Fundamental Technology Researches of the Ministry of Education, Culture, Sports, Science and Technology, Japan.

Synthesis, crystal structure, catalytic and anti-Trypanosoma cruzi activity of a new chromium(III) complex containing bis(3,5-dimethylpyrazol-1-yl)methane

NASA Astrophysics Data System (ADS)

Hurtado, John; Ibarra, Laura; Yepes, David; García-Huertas, Paola; Macías, Mario A.; Triana-Chavez, Omar; Nagles, Edgar; Suescun, Leopoldo; Muñoz-Castro, Alvaro

2017-10-01

The reaction of CrCl36H2O with the ligand bis(3,5-dimethylpyrazol-1-yl)methane (L) yielded the cationic complex [(Cr(L)(H2O)2Cl2]+, which crystallized as the chloride trihydrate [(Cr(L)(H2O)2Cl2]Cl·3H2O. The chromium complex was characterized by elemental analysis, electrical conductivity, Infrared and Ultraviolet/Visible spectroscopy. The crystal structure determination using single-crystal X-ray diffraction showed a chromium center in a distorted octahedral coordination sphere. In the crystal, the packing was directed by Osbnd H⋯(O,Cl) hydrogen bonds and weak Csbnd H⋯O interactions to build a monoclinic P21/c supramolecular structure. The complex showed excellent properties as an initiator for the ring opening polymerization of є-caprolactone (CL) under solvent-free conditions. The obtained polymer showed high crystallinity (89.9%) and a decomposition temperature above 475 °C. In addition, the new complex was evaluated against epimastigotes from Trypanosoma cruzi (T. cruzi) strains. The results indicated that this complex has a high activity against this parasite with a minimum inhibitory concentration 50 (MIC50) of 1.08 μg/mL. Interestingly, this compound showed little effect on erythrocytes, indicating that it is not cytotoxic. These results provide interesting contributions to the design of metal complexes by using simple and accessible ligands with activity against T. cruzi and with potential applications in the polymerization of CL.

Modeling two-dimensional crystals and nanotubes with defects under stress

NASA Astrophysics Data System (ADS)

Dietel, Jürgen; Kleinert, Hagen

2009-06-01

We calculate analytically the phase diagram of a two-dimensional planar crystal and its wrapped version with defects under external homogeneous stress as a function of temperature using a simple elastic square lattice model that allows for defect formation. The temperature dependence turns out to be very weak. The results are relevant for recent stress experiments on carbon nanotubes at high temperatures. Under increasing stress, we find a crossover regime which we identify with a cracking transition that is almost independent of temperature. Furthermore, we find an almost stress-independent melting point. In addition, we derive an enhanced ductility with relative strains before cracking between 200% and 400%, in agreement with carbon nanotube experiments. The specific values depend on the Poisson ratio and the angle between the external force and the crystal axes. We give arguments that the results for carbon nanotubes should be not much different from these results in spite of the different lattice structures.

Synthesis, crystal structure and computational studies of a new Schiff base compound: (E)-4-bromo-2-eth-oxy-6-{[(2-meth-oxy-phen-yl)imino]meth-yl}phenol.

PubMed

Özek Yıldırım, Arzu; Gülsu, Murat; Albayrak Kaştaş, Çiğdem

2018-03-01

The title compound, C 16 H 16 BrNO 3 , which shows enol-imine tautomerism, crystallizes in the monoclinic P 2 1 / c space group. All non-H atoms of the mol-ecule are nearly coplanar, with a maximum deviation of 0.274 (3) Å. In the crystal, mol-ecules are held together by weak C-H⋯O, π-π and C-H⋯π inter-actions. The E / Z isomerism and enol/keto tautomerism energy barriers of the compound have been calculated by relaxed potential energy surface scan calculations with DFT methods. To observe the changes in the aromatic ring, HOMA aromaticity indexes were calculated during the scan process. Total energy and HOMA change curves were obtained to visualize results of the scan calculations.

Ferromagnetic Switching of Knotted Vector Fields in Liquid Crystal Colloids.

PubMed

Zhang, Qiaoxuan; Ackerman, Paul J; Liu, Qingkun; Smalyukh, Ivan I

2015-08-28

We experimentally realize polydomain and monodomain chiral ferromagnetic liquid crystal colloids that exhibit solitonic and knotted vector field configurations. Formed by dispersions of ferromagnetic nanoplatelets in chiral nematic liquid crystals, these colloidal ferromagnets exhibit spontaneous long-range alignment of magnetic dipole moments of individual platelets, giving rise to a continuum of the magnetization field M(r). Competing effects of surface confinement and chirality prompt spontaneous formation and enable the optical generation of localized twisted solitonic structures with double-twist tubes and torus knots of M(r), which exhibit a strong sensitivity to the direction of weak magnetic fields ∼1  mT. Numerical modeling, implemented through free energy minimization to arrive at a field-dependent three-dimensional M(r), shows a good agreement with experiments and provides insights into the torus knot topology of observed field configurations and the corresponding physical underpinnings.

Paramagnetic resonance and susceptibility of ilmenite, FeTiO3 crystal

NASA Technical Reports Server (NTRS)

Mcdonald, P. F.; Parasiris, A.; Pandey, R. K.; Gries, B. L.; Kirk, W. P.

1991-01-01

Large high-purity single crystals of FeTiO3 with ilmenite structure have been grown from a stoichiometric melt of Fe2O3 and TiO2 under an inert atmosphere using the modified Czochralski technique. Susceptibility and X-band paramagnetic resonance studies have been performed. Susceptibility measurements indicate a Neel temperature of about 59 K. The paramagnetic resonance spectrum for magnetic field perpendicular to the crystal c axis consists of a portion of a single, very intense approximately Lorentzian absorption line with its peak at about 600 G and half width at half maximum almost 1200 G. The absorption extends to zero magnetic field. For magnetic field approximately parallel to the c axis, the paramagnetic absorption is much smaller and may be considered a superposition of two approximately Lorentzian line shapes. The magnetic resonance measurements indicate a weak temperature dependence and large angular anisotropy.

Structural and computational analysis of intermolecular interactions in a new 2-thiouracil polymorph.

PubMed

Fabijanić, Ivana; Matković-Čalogović, Dubravka; Pilepić, Viktor; Sanković, Krešimir

2017-12-01

The crystallization and characterization of a new polymorph of 2-thiouracil by single-crystal X-ray diffraction, Hirshfeld surface analysis and periodic density functional theory (DFT) calculations are described. The previously published polymorph (A) crystallizes in the triclinic space group P\\overline{1}, while that described herein (B) crystallizes in the monoclinic space group P2 1 /c. Periodic DFT calculations showed that the energies of polymorphs A and B, compared to the gas-phase geometry, were -108.8 and -29.4 kJ mol -1 , respectively. The two polymorphs have different intermolecular contacts that were analyzed and are discussed in detail. Significant differences in the molecular structure were found only in the bond lengths and angles involving heteroatoms that are involved in hydrogen bonds. Decomposition of the Hirshfeld fingerprint plots revealed that O...H and S...H contacts cover over 50% of the noncovalent contacts in both of the polymorphs; however, they are quite different in strength. Hydrogen bonds of the N-H...O and N-H...S types were found in polymorph A, whereas in polymorph B, only those of the N-H...O type are present, resulting in a different packing in the unit cell. QTAIM (quantum theory of atoms in molecules) computational analysis showed that the interaction energies for these weak-to-medium strength hydrogen bonds with a noncovalent or mixed interaction character were estimated to fall within the ranges 5.4-10.2 and 4.9-9.2 kJ mol -1 for polymorphs A and B, respectively. Also, the NCI (noncovalent interaction) plots revealed weak stacking interactions. The interaction energies for these interactions were in the ranges 3.5-4.1 and 3.1-5.5 kJ mol -1 for polymorphs A and B, respectively, as shown by QTAIM analysis.

Synthesis, structure and properties of blödite-type solid solutions, Na2Co1-x Cu x (SO4)2·4H2O (0 < x ≤ 0.18), and crystal structure of synthetic kröhnkite, Na2Cu(SO4)2·2H2O

NASA Astrophysics Data System (ADS)

Marinova, Delyana; Wildner, Manfred; Bancheva, Tsvetelina; Stoyanova, Radostina; Georgiev, Mitko; Stoilova, Donka G.

2018-03-01

Based on different experimental methods—crystallization processes in aqueous solutions, infrared spectroscopy, single-crystal X-ray diffraction, electron paramagnetic resonance (EPR) and TG-DTA-DSC measurements—it has been established that copper ions are included in sodium cobalt sulfate up to about 18 mol%, thus forming limited solid solutions Na2Co1-x Cu x (SO4)2·4H2O (0 < x ≤ 0.18) with a blödite-type structure. In contrast, cobalt ions are not able to accept the coordination environment of the copper ions in the strongly distorted Cu(H2O)2O4 octahedra, thus resulting in the crystallization of Co-free kröhnkite. The solid solutions were characterized by vibrational and EPR spectroscopy. DSC measurements reveal that the copper concentration increase leads to increasing values of the enthalpy of dehydration (ΔH deh) and decreasing values of the enthalpy of formation (ΔH f). The crystal structures of synthetic kröhnkite, Na2Cu(SO4)2·2H2O, as well as of three Cu2+-bearing mixed crystals of Co-blödite, Na2Co1-x Cu x (SO4)2·4H2O with x (Cu) ranging from 0.03 to 0.15, have been investigated from single-crystal X-ray diffraction data. The new data for the structure of synthetic kröhnkite facilitated to clarify structural discrepancies found in the literature for natural kröhnkite samples, traced back to a mix-up of lattice parameters. The crystal structures of Co-dominant Na2Co1-x Cu x (SO4)2·4H2O solid solutions reveal a comparatively weak influence of the Jahn-Teller-affected Cu2+ guest cations up to the maximum content of x (Cu) = 0.15. The response of the MO2(H2O)4 octahedral shape by increased bond-length distortion with Cu content is clear cut (but limited), mainly concerning the M-OH2 bond lengths, whereas other structural units are hardly affected. However, the specific type of imposed distortion seems to play an important role impeding higher Cu/Co replacement ratios.

Crystal structure of (E)-4-hy-droxy-N'-(3-meth-oxy-benzyl-idene)benzohydrazide.

PubMed

Chantrapromma, Suchada; Prachumrat, Patcharawadee; Ruanwas, Pumsak; Boonnak, Nawong; Kassim, Mohammad B

2016-09-01

The title compound, C 15 H 14 N 2 O 3 , crystallizes with two independent mol-ecules ( A and B ) in the asymmetric unit that differ in the orientation of the 3-meth-oxy-phenyl group with respect to the methyl-idenebenzohydrazide unit. The dihedral angles between the two benzene rings are 24.02 (10) and 29.30 (9)° in mol-ecules A and B , respectively. In mol-ecule A , the meth-oxy group is twisted slightly relative to its bound benzene ring, with a C meth-yl -O-C-C torsion angle of 14.2 (3)°, whereas it is almost co-planar in mol-ecule B , where the corresponding angle is -2.4 (3)°. In the crystal, the mol-ecules are linked by N-H⋯O, O-H⋯N and O-H⋯O hydrogen bonds, as well as by weak C-H⋯O inter-actions, forming sheets parallel to the bc plane. The N-H⋯O hydrogen bond and weak C-H⋯O inter-action link different mol-ecules ( A ⋯ B ) whereas both O-H⋯N and O-H⋯O hydrogen bonds link like mol-ecules ( A ⋯ A ) and ( B ⋯ B ). Pairs of inversion-related B mol-ecules are stacked approximately along the a axis by π-π inter-actions in which the distance between the centroids of the 3-meth-oxy-phenyl rings is 3.5388 (12) Å. The B mol-ecules also participate in weak C-H⋯π inter-actions between the 4-hy-droxy-phenyl and the 3-meth-oxy-phenyl rings.

Synthesis, crystal structures, and optical properties of the π-π interacting pyrrolo[2,3-b]quinoxaline derivatives containing 2-thienyl substituent

NASA Astrophysics Data System (ADS)

Goszczycki, Piotr; Stadnicka, Katarzyna; Brela, Mateusz Z.; Grolik, Jarosław; Ostrowska, Katarzyna

2017-10-01

Three (E/Z)-diastereoisomers, based on pyrrolo[2,3-b]quinoxaline system as fluorophore and containing: 2-thienylmethyl (1), bis(2-thienylmethyl)-2-aminoethyl (3a), bis(2-thienylmethyl)-3-aminopropyl (3b) groups as substituents, were synthesized and characterized by X-ray structural analysis, PXRD, NMR, UV-Vis as well as fluorescence. These compounds are non-fluorescent in acetonitrile solution, however, they exhibit aggregation induced emission enhancement (AIEE) upon water addition and in solid state. X-ray structural analysis revealed that molecules with 2-thienylmethyl and bis(2-thienylmethyl)-2-aminoethyl groups form dimers and π-stacks through π-π interactions between anitiparallel oriented pyrroloquinoxaline cores with interplanar distances 3.45 Å and 3.20 Å, respectively. Conformation of bis(2-thienylmethyl)-3-aminopropyl group is imposed by incorporated DMSO-d6 solvent molecule and weak intermolecular S-π and CH-π interactions, that prevents π-π interaction between fluorophore cores. The correlation between crystal structure and fluorescent properties of synthesized molecules was discussed. The DFT calculations were performed to rationalize the differences between considered systems.

A facile chemical conversion synthesis of Sb2S3 nanotubes and the visible light-driven photocatalytic activities

PubMed Central

2012-01-01

We report a simple chemical conversion and cation exchange technique to realize the synthesis of Sb2S3 nanotubes at a low temperature of 90°C. The successful chemical conversion from ZnS nanotubes to Sb2S3 ones benefits from the large difference in solubility between ZnS and Sb2S3. The as-grown Sb2S3 nanotubes have been transformed from a weak crystallization to a polycrystalline structure via successive annealing. In addition to the detailed structural, morphological, and optical investigation of the yielded Sb2S3 nanotubes before and after annealing, we have shown high photocatalytic activities of Sb2S3 nanotubes for methyl orange degradation under visible light irradiation. This approach offers an effective control of the composition and structure of Sb2S3 nanomaterials, facilitates the production at a relatively low reaction temperature without the need of organics, templates, or crystal seeds, and can be extended to the synthesis of hollow structures with various compositions and shapes for unique properties. PMID:22448960

DOE Office of Scientific and Technical Information (OSTI.GOV)

Z Xu; C Chen; Y Wang

Combined effects of graphene nanosheets (GNSs) and shear flow on the crystallization behavior of isotactic polypropylene (iPP) were investigated by in-situ synchrotron wide-angle X-ray diffraction (WAXD) and small-angle X-ray scattering (SAXS) techniques. For crystallization under quiescent condition (at 145 C), the half-crystallization time (t{sub 1/2}) of nanocomposites containing 0.05 and 0.1 wt % GNSs was reduced to at least 50% compared to that of neat iPP, indicating the high nucleation ability of GNSs. The crystallization rate of iPP was directly proportional to the GNS content. Under a relatively weak shear flow (at a rate of 20 s{sup -1} for 5more » s duration) and a low degree of supercooling, the neat iPP exhibited an isotropic structure due to the relaxation of row nuclei. However, visible antisotropic crystals appeared in sheared iPP/GNSs nanocomposites, indicating that GNSs induced a network structure hindering the mobility of iPP chains and allowing the survival of oriented row nuclei for a long period of time. The presence of GNSs clearly enhanced the effects of shear-induced nucleation as well as orientation of iPP crystals. Two kinds of nucleating origins coexisted in the sheared nanocomposite melt: heterogeneous nucleating sites initiated by GNSs and homogeneous nucleating sites (row nuclei) induced by shear. The difference of t{sub 1/2} of nanocomposites with and without shear was significantly larger than that of neat iPP. The presence of GNSs and shear flow exhibited a synergistic interaction on promoting crystallization kinetics of iPP, although the effect of GNS concentration was not apparent. From WAXD results of isothermal and nonisothermal crystallization of sheared iPP, it was found that the appearance of {beta}-crystals depended on the preservation of row nuclei, where the {alpha}-crystals were predominant in the iPP/GNSs nanocomposites, indicating that GNSs could directly induce {alpha}-crystals of iPP.« less

Impact of Heterogeneity and Lattice Bond Strength on DNA Triangle Crystal Growth.

PubMed

Stahl, Evi; Praetorius, Florian; de Oliveira Mann, Carina C; Hopfner, Karl-Peter; Dietz, Hendrik

2016-09-07

One key goal of DNA nanotechnology is the bottom-up construction of macroscopic crystalline materials. Beyond applications in fields such as photonics or plasmonics, DNA-based crystal matrices could possibly facilitate the diffraction-based structural analysis of guest molecules. Seeman and co-workers reported in 2009 the first designed crystal matrices based on a 38 kDa DNA triangle that was composed of seven chains. The crystal lattice was stabilized, unprecedentedly, by Watson-Crick base pairing. However, 3D crystallization of larger designed DNA objects that include more chains such as DNA origami remains an unsolved problem. Larger objects would offer more degrees of freedom and design options with respect to tailoring lattice geometry and for positioning other objects within a crystal lattice. The greater rigidity of multilayer DNA origami could also positively influence the diffractive properties of crystals composed of such particles. Here, we rationally explore the role of heterogeneity and Watson-Crick interaction strengths in crystal growth using 40 variants of the original DNA triangle as model multichain objects. Crystal growth of the triangle was remarkably robust despite massive chemical, geometrical, and thermodynamical sample heterogeneity that we introduced, but the crystal growth sensitively depended on the sequences of base pairs next to the Watson-Crick sticky ends of the triangle. Our results point to weak lattice interactions and high concentrations as decisive factors for achieving productive crystallization, while sample heterogeneity and impurities played a minor role.

Late-stage sinking of plutons

USGS Publications Warehouse

Glazner, A.F.; Miller, D.M.

1997-01-01

Many granodiorite to diorite plutons in the Great Basin of western North America are surrounded by rim monoclines or anticlines that suggest relative downward movement of the plutons while wall rocks were hot and ductile. We propose that such plutons rise to a level of approximately neutral buoyancy and then founder as their densities increase ??? 40% during crystallization. Late-stage sinking of intermediate to mafic plutons should be common when wall rocks are rich in weak, low-density minerals such as quartz and calcite. Structures related to sinking will overprint those related to initial pluton emplacement and may be mistaken for regional tectonic structures.

Synthesis and the crystal and molecular structure of the germanium(IV) complex with propylene-1,3-diaminetetraacetic acid [Ge(Pdta)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sergienko, V. S., E-mail: sergienko@igic.ras.ru; Martsinko, E. E.; Seifullina, I. I.

2015-09-15

The germanium(IV) complex with propylene-1,3-diaminetetraacetic acid (H{sub 4}Pdta) is studied by elemental analysis, X-ray diffraction, thermogravimetry, and IR spectroscopy. The X-ray diffraction study reveals two crystallographically independent [Ge(Pdta)] molecules of similar structure. Both Ge atoms are octahedrally coordinated by four O atoms and two N atoms (at the cis positions) of the hexadentate pentachelate Pdta{sup 4–} ligand. An extended system of weak C—H···O hydrogen bonds connects complex molecules into a supramolecular 3D framework.

Synthesis and the crystal and molecular structure of the germanium(IV) complex with propylene-1,3-diaminetetraacetic acid [Ge( Pdta)

NASA Astrophysics Data System (ADS)

Sergienko, V. S.; Martsinko, E. E.; Seifullina, I. I.; Churakov, A. V.; Chebanenko, E. A.

2015-09-01

The germanium(IV) complex with propylene-1,3-diaminetetraacetic acid (H4 Pdta) is studied by elemental analysis, X-ray diffraction, thermogravimetry, and IR spectroscopy. The X-ray diffraction study reveals two crystallographically independent [Ge( Pdta)] molecules of similar structure. Both Ge atoms are octahedrally coordinated by four O atoms and two N atoms (at the cis positions) of the hexadentate pentachelate Pdta 4- ligand. An extended system of weak С—Н···О hydrogen bonds connects complex molecules into a supramolecular 3D framework.

Radical-lanthanide ferromagnetic interaction in a T bIII bis-phthalocyaninato complex

NASA Astrophysics Data System (ADS)

Komijani, Dorsa; Ghirri, Alberto; Bonizzoni, Claudio; Klyatskaya, Svetlana; Moreno-Pineda, Eufemio; Ruben, Mario; Soncini, Alessandro; Affronte, Marco; Hill, Stephen

2018-02-01

Recent studies have highlighted the importance of organic ligands in the field of molecular spintronics, via which delocalized electron-spin density can mediate magnetic coupling to otherwise localized 4 f moments of lanthanide ions, which show tremendous potential for single-molecule device applications. To this end, high-field/high-frequency electron paramagnetic resonance (EPR) spectroscopy is employed to study a neutral terbium bis-phthalocyaninato metalorganic complex, [TbPc2 ] 0, with the aim of understanding the magnetic interaction between the Ising-like moment of the lanthanide ion and the unpaired spin density on the coordinating organic radical ligand. The measurements were performed on a previously unknown [TbPc2 ] 0 structural phase crystallizing in the Pnma space group. EPR measurements on powder samples of [TbPc2 ] 0 reveal an anisotropic spectrum, which is attributed to the spin-1/2 radical coupled weakly to the EPR-silent T bIII ion. Extensive double-axis rotation studies on a single crystal reveal two independent spin-1/2 signals with differently oriented (albeit identical) uniaxial g -tensors, in complete agreement with x-ray structural studies that indicate two molecular orientations within the unit cell. The easy-axis nature of the radical EPR spectra thus reflects the coupling to the Ising-like T bIII moment. This is corroborated by studies of the isostructural [YPc2 ] 0 analog (where Y is nonmagnetic yttrium), which gives a completely isotropic radical EPR signal. The experimental results for the terbium complex are well explained on the basis of an effective model that introduces a weak ferromagnetic Heisenberg coupling between an isotropic spin-1/2 and an anisotropic spin-orbital moment, J =6 , that mimics the known, strong easy-axis Tb ⋯P c2 crystal-field interaction.

Optical coherence of 166Er:7LiYF4 crystal below 1 K

NASA Astrophysics Data System (ADS)

Kukharchyk, N.; Sholokhov, D.; Morozov, O.; Korableva, S. L.; Kalachev, A. A.; Bushev, P. A.

2018-02-01

We explore optical coherence and spin dynamics of an isotopically purified 166Er:7LiYF4 crystal below 1 K and at weak magnetic fields < 0.3T. Crystals were grown in our lab and demonstrate narrow inhomogeneous optical broadening down to 16 MHz. Solid-state atomic ensembles with such narrow linewidths are very attractive for implementing of off-resonant Raman quantum memory and for the interfacing of superconducting quantum circuits and telecom C-band optical photons. Both applications require a low magnetic field of ∼10 mT. However, at conventional experimental temperatures T > 1.5 K, optical coherence of Er:LYF crystal attains ≃ 10 μ {{s}} time scale only at strong magnetic fields above 1.5 T. In the present work, we demonstrate that the deep freezing of Er:LYF crystal below 1 K results in the increase of optical coherence time to ≃ 100 μ {{s}} at weak fields.

Persistent magnetism in silver-doped BaF e 2 A s 2 crystals

DOE PAGES

Li, Li; Cao, Huibo; Parker, David S.; ...

2016-10-12

Here, we investigate the thermodynamic and transport properties of silver-substituted BaF e 2 A s 2 (122) crystals up to ~ 4.5 % . Similar to other transition-metal substitutions in 122, Ag diminishes the antiferromagnetic ( T N ) and structural ( T S ) transition temperatures, but unlike other electron-doped 122s, T N and T S coincide without splitting. Though magnetism drops precipitously to T N = 84 K at doping x = 0.029 , it only weakly changes above this x , settling at T N = 80 K at x = 0.045 . Compared to this persistentmore » magnetism in Ag-122, doping other group 11 elements of either Cu or Au in 122 diminished T N and induced superconductivity near T c = 2 K at x = 0.044 or 0.031, respectively. Ag-122 crystals show reflective surfaces with surprising thicker cross sections for x ≥ 0.019 , the appearance that is in contrast to the typical thin stacked layered feature seen in all other flux-grown x-122 and lower Ag-122. We found that this physical trait may be a manifest of intrinsic weak changes in c lattice and T N . Our theoretical calculations suggest that Ag doping produces strong electronic scattering and yet a relatively small disruption of the magnetic state, both of which preclude superconductivity in this system.« less

Nonlinear optical and electroabsorption spectra of polydiacetylene crystals and films

NASA Astrophysics Data System (ADS)

Mukhopadhyay, D.; Soos, Z. G.

1996-01-01

Vibronic structure of nonlinear optical (NLO) coefficients is developed within the Condon approximation, displaced harmonic oscillators, and crude adiabatic states. The displacements of backbone modes of conjugated polymers are taken from vibrational data on the ground and 1B excited state. NLO resonances are modeled by three excitations and transition moments taken from Pariser-Parr-Pople (PPP) theory and optimized to polydiacetylene (PDA) spectra in crystals and films, with blue-shifted 1B exciton. The joint analysis of third-harmonic-generation, two-photon absorption, and nondegenerate four-wave-mixing spectra of PDA crystals and films shows weak two-photon absorption to 2A below 1B, leading to overlapping resonances in the THG spectrum, strong two-photon absorption to an nA state some 35% above 1B, and weak Raman resonances in nondegenerate FWM spectra. The full π-π* spectrum contributes to Stark shifts and field-induced transitions, as shown by PPP results for PDA oligomers. The Stark shift dominates high-resolution electroabsorption (EA) spectra of PDA crystals below 10 K. The close correspondence between EA and the first-derivative I'(ω) of the linear absorption above the 1B exciton in PDA crystals provides an experimental separation of vibrational and electronic contributions that limits any even-parity state in this 0.5 eV interval. An oscillator-strength sum rule is applied to the convergence of PDA oligomers with increasing length, N, and the crystal oscillator strengths are obtained without adjustable parameters. The sum rule for the 1B exciton implies large transition moments to higher-energy Ag states, whose locations in recent models are contrasted to PPP results. Joint analysis of NLO and EA spectra clarifies when a few electronic excitations are sufficient, distinguishes between vibrational and electronic contributions, and supports similar π-electron interactions in conjugated molecules and polymers.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kaluarachchi, Udhara S.; Xie, Weiwei; Lin, Qisheng

Single crystals of Bi 2Rh 3S 2 and Bi 2Rh 3.5S 2 were synthesized by solution growth, and the crystal structures and thermodynamic and transport properties of both compounds were studied. In the case of Bi 2Rh 3S 2, a structural first-order transition at around 165 K is identified by single-crystal diffraction experiments, with clear signatures visible in resistivity, magnetization, and specific heat data. No superconducting transition for Bi 2Rh 3S 2 was observed down to 0.5 K. In contrast, no structural phase transition at high temperature was observed for Bi 2Rh 3.5S 2; however, bulk superconductivity with a criticalmore » temperature, T c ≈ 1.7 K, was observed. The Sommerfeld coefficient γ and the Debye temperature (Θ D) were found to be 9.41 mJ mol –1K –2 and 209 K, respectively, for Bi 2Rh 3S 2, and 22 mJ mol –1K –2 and 196 K, respectively, for Bi 2Rh 3.5S 2. As a result, the study of the specific heat in the superconducting state of Bi 2Rh 3.5S 2 suggests that Bi 2Rh 3.5S 2 is a weakly coupled, BCS superconductor.« less

The local structure and ferromagnetism in Fe-implanted SrTiO3 single crystals

NASA Astrophysics Data System (ADS)

Lobacheva, O.; Chavarha, M.; Yiu, Y. M.; Sham, T. K.; Goncharova, L. V.

2014-07-01

We report a connection between the local structure of low-level Fe impurities and vacancies as the cause of ferromagnetic behavior observed in strontium titanate single crystals (STO), which were implanted with Fe and Si ions at different doses then annealed in oxygen. The effects of Fe doping and post-implantation annealing of STO were studied by X-ray Absorption Near Edge Structure (XANES) spectroscopy and Superconducting Quantum Interference Device magnetometry. XANES spectra for Fe and Ti K- and L-edge reveal the changes in the local environment of Fe and Ti following the implantation and annealing steps. The annealing in oxygen atmosphere partially healed implantation damages and changed the oxidation state of the implanted iron from metallic Fe0 to Fe2+/Fe3+ oxide. The STO single crystals were weak ferromagnets prior to implantation. The maximum saturation moment was obtained after our highest implantation dose of 2 × 1016 Fe atom/cm2, which could be correlated with the metallic Fe0 phases in addition to the presence of O/Ti vacancies. After recrystallization annealing, the ferromagnetic response disappears. Iron oxide phases with Fe2+ and Fe3+ corresponding to this regime were identified and confirmed by calculations using Real Space Multiple Scattering program (FEFF9).

Initial Steps of Rubicene Film Growth on Silicon Dioxide.

PubMed

Scherwitzl, Boris; Lukesch, Walter; Hirzer, Andreas; Albering, Jörg; Leising, Günther; Resel, Roland; Winkler, Adolf

2013-02-28

The film growth of the conjugated organic molecule rubicene on silicon dioxide was studied in detail. Since no structural data of the condensed material were available, we first produced high quality single crystals from solution and determined the crystal structure. This high purity material was used to prepare ultrathin films under ultrahigh vacuum conditions, by physical vapor deposition. Thermal desorption spectroscopy (TDS) was applied to delineate the adsorption and desorption kinetics. It could be shown that the initial sticking coefficient is only 0.2 ± 0.05, but the sticking coefficient increases with increasing coverage. TDS further revealed that first a closed, weakly bound bilayer develops (wetting layer), which dewets after further deposition of rubicene, leading to an island-like layer. These islands are crystalline and exhibit the same structure as the solution grown crystals. The orientation of the crystallites is with the (001) plane parallel to the substrate. A dewetting of the closed bilayer was also observed when the film was exposed to air. Furthermore, Ostwald ripening of the island-like film takes place under ambient conditions, leading to films composed of few, large crystallites. From TDS, we determined the heat of evaporation from the multilayer islands to be 1.47 eV, whereas the desorption energy from the first layer is only 1.25 eV.

Initial Steps of Rubicene Film Growth on Silicon Dioxide

PubMed Central

2013-01-01

The film growth of the conjugated organic molecule rubicene on silicon dioxide was studied in detail. Since no structural data of the condensed material were available, we first produced high quality single crystals from solution and determined the crystal structure. This high purity material was used to prepare ultrathin films under ultrahigh vacuum conditions, by physical vapor deposition. Thermal desorption spectroscopy (TDS) was applied to delineate the adsorption and desorption kinetics. It could be shown that the initial sticking coefficient is only 0.2 ± 0.05, but the sticking coefficient increases with increasing coverage. TDS further revealed that first a closed, weakly bound bilayer develops (wetting layer), which dewets after further deposition of rubicene, leading to an island-like layer. These islands are crystalline and exhibit the same structure as the solution grown crystals. The orientation of the crystallites is with the (001) plane parallel to the substrate. A dewetting of the closed bilayer was also observed when the film was exposed to air. Furthermore, Ostwald ripening of the island-like film takes place under ambient conditions, leading to films composed of few, large crystallites. From TDS, we determined the heat of evaporation from the multilayer islands to be 1.47 eV, whereas the desorption energy from the first layer is only 1.25 eV. PMID:23476720

Influence of the anions on the N-cationic benzethonium salts in the solid state and solution: Chloride, bromide, hydroxide and citrate hydrates

NASA Astrophysics Data System (ADS)

Paradies, Henrich H.; Reichelt, Hendrik

2016-06-01

The crystal structures of the hydrated cationic surfactant benzethonium (Bzth) chloride, bromide, hydroxide, and citrate have been determined by X-ray diffraction analysis and compared with their structures in solution well above their critical micelle concentration. The differences in the nature of the various anions of the four Bzth-X materials lead to unique anion environments and 3-D molecular arrangements. The water molecule in the monoclinic Bzth-Cl or Bzth-Br forms is hydrogen bonded to the halides and particularly to the hydrogens of the methoxy groups of the Bzth moiety notwithstanding the weak Brønsted acidity of the methoxy hydrogens. The citrate strongly interacts with the hydrogens of the methoxy group forming an embedded anionic spherical cluster of a radius of 2.6 Å. The Bzth-OH crystallizes in a hexagonal lattice with two water molecules and reveals free water molecules forming hydrogen bonded channels through the Bzth-OH crystal along the c-axis. The distances between the cationic nitrogen and the halides are 4.04 Å and 4.20 Å, significantly longer than expected for typical van der Waals distances of 3.30 Å. The structures show weakly interacting, alternating apolar and polar layers, which run parallel to the crystallographic a-b planes or a-c planes. The Bzth-X salts were also examined in aqueous solution containing 20% (v/v) ethanol and 1.0 % (v/v) glycerol well above their critical micelle concentration by small-angle X-ray scattering (SAXS) and wide-angle X-ray scattering (WAXS). The [1,1,1] planes for the Bzth Cl or Br, the [0,0,2] and [1,1,0] planes for the Bzth-citrate, the [2,-1,0] planes and the [0,0,1] planes for the Bzth-OH found in the crystalline phase were also present in the solution phase, accordingly, the preservation of these phases are a strong indication of periodicity in the solution phase.

2,2'-(Carbono-thio-yldisulfanedi-yl)bis-(2-methyl-propanoic acid).

PubMed

Moreno-Fuquen, Rodolfo; Grande, Carlos; Advincula, Rigoberto C; Tenorio, Juan C; Ellena, Javier

2013-05-01

The mol-ecular structure of the title compound, C9H14O4S3, exhibits intra-molecular C-H⋯S hydrogen bonds. In the crystal, pairs of O-H⋯O hydrogen bonds lead to the formation of centrosymmetric dimers, which are in turn connected by weak C-H⋯O inter-actions. The combination of these inter-actions generates edge-fused R 2 (2)(8) and R 2 (2)(20) rings running along [211].

1,5-Bis[(E)-cyclo-pentyl-idene]thio-carbono-hydrazide.

PubMed

Guo, Qingliang; Sun, Junshan; Li, Jikun; Wu, Rentao; Duan, Wenzeng

2009-03-25

In the title mol-ecule, C(11)H(18)N(4)S, an intra-molecular N-H⋯N hydrogen bond [N⋯N = 2.558 (3)Å] is observed. The two cyclo-pentyl rings are disordered between two conformations in 1:1 and 2:1 ratios. In the crystal structure, weak inter-molecular N-H⋯S hydrogen bonds [N⋯S = 3.547 (3) Å] link pairs of mol-ecules into centrosymmetric dimers.

Magnetic phase dependence of the anomalous Hall effect in Mn 3Sn single crystals

DOE PAGES

Sung, Nakheon H.; Ronning, Filip; Thompson, Joe David; ...

2018-03-29

Thermodynamic and transport properties are reported on single crystals of the hexagonal antiferromagnet Mn 3Sn grown by the Sn flux technique. Magnetization measurements reveal two magnetic phase transitions at T 1 = 275 K and T 2 = 200 K, below the antiferromagnetic phase transition at T N ≈ 420 K. The Hall conductivity in zero magnetic field is suppressed dramatically from 4.7 Ω -1 cm -1 to near zero below T 1, coincident with the vanishing of the weak ferromagnetic moment. Finally, this illustrates that the large anomalous Hall effect arising from the Berry curvature can be switched onmore » and off by a subtle change in the symmetry of the magnetic structure near room temperature.« less

Nearly-free-electron system of monolayer Na on the surface of single-crystal HfSe 2

DOE PAGES

Eknapakul, T.; Fongkaew, I.; Siriroj, S.; ...

2016-11-15

Here, the electronic structure of a single Na monolayer on the surface of single-crystal HfSe 2 is investigated using angle-resolved photoemission spectroscopy. We find that this system exhibits an almost perfect "nearly-free-electron" behavior with an extracted effective mass of ~1m e, in contrast to heavier masses found previously for alkali-metal monolayers on other substrates. Our density-functional-theory calculations indicate that this is due to the large lattice constant, causing both exchange and correlation interactions to be suppressed, and to the weak hybridization between the overlayer and the substrate. This is therefore an ideal model system for understanding the properties of two-dimensionalmore » materials.« less

Magnetic phase dependence of the anomalous Hall effect in Mn 3Sn single crystals

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sung, Nakheon H.; Ronning, Filip; Thompson, Joe David

Thermodynamic and transport properties are reported on single crystals of the hexagonal antiferromagnet Mn 3Sn grown by the Sn flux technique. Magnetization measurements reveal two magnetic phase transitions at T 1 = 275 K and T 2 = 200 K, below the antiferromagnetic phase transition at T N ≈ 420 K. The Hall conductivity in zero magnetic field is suppressed dramatically from 4.7 Ω -1 cm -1 to near zero below T 1, coincident with the vanishing of the weak ferromagnetic moment. Finally, this illustrates that the large anomalous Hall effect arising from the Berry curvature can be switched onmore » and off by a subtle change in the symmetry of the magnetic structure near room temperature.« less

Crystal structure of 1-ferrocenyl-2-(4-methyl-benzo-yl)spiro-[11H-pyrrolidizine-3,11'-indeno[1,2-b]quinoxaline].

PubMed

Chandralekha, Kuppan; Gavaskar, Deivasigamani; Sureshbabu, Adukamparai Rajukrishnan; Lakshmi, Srinivasakannan

2014-09-01

In the title compound, [Fe(C5H5)(C34H28N3O)], the four-fused-rings system of the 11H-indeno-[1,2-b]quinoxaline unit is approximately planar [maximum deviation = 0.167 (4) Å] and forms a dihedral angle of 37.25 (6)° with the plane of the benzene ring of the methyl-benzoyl group. Both pyrrolidine rings adopt a twist conformation. An intra-molecular C-H⋯O hydrogen bond is observed. In the crystal, mol-ecules are linked by C-H⋯O hydrogen bonds and weak C-H⋯π inter-actions, forming double chains extending parallel to the c axis.

Ising-like spin anisotropy and competing antiferromagnetic-ferromagnetic orders in GdBaCo2O5.5 single crystals.

PubMed

Taskin, A A; Lavrov, A N; Ando, Yoichi

2003-06-06

In RBaCo2O5+x compounds (R is rare earth), a ferromagnetic-antiferromagnetic competition is accompanied by a giant magnetoresistance. We study the magnetization of detwinned GdBaCo2O5.5 single crystals and find a remarkable uniaxial anisotropy of Co3+ spins which is tightly linked with the chain oxygen ordering in GdO0.5 planes. Reflecting the underlying oxygen order, CoO2 planes also develop a spin-state order consisting of Co3+ ions in alternating rows of S=1 and S=0 states. The magnetic structure appears to be composed of weakly coupled ferromagnetic ladders with Ising-like moments, which gives a simple picture for magnetotransport phenomena.

Magnetic phase dependence of the anomalous Hall effect in Mn3Sn single crystals

NASA Astrophysics Data System (ADS)

Sung, N. H.; Ronning, F.; Thompson, J. D.; Bauer, E. D.

2018-03-01

Thermodynamic and transport properties are reported on single crystals of the hexagonal antiferromagnet Mn3Sn grown by the Sn flux technique. Magnetization measurements reveal two magnetic phase transitions at T1 = 275 K and T2 = 200 K, below the antiferromagnetic phase transition at TN ≈ 420 K. The Hall conductivity in zero magnetic field is suppressed dramatically from 4.7 Ω-1 cm-1 to near zero below T1, coincident with the vanishing of the weak ferromagnetic moment. This illustrates that the large anomalous Hall effect arising from the Berry curvature can be switched on and off by a subtle change in the symmetry of the magnetic structure near room temperature.

Crystal structure and Hirshfeld surface analysis of ethyl 2-{[4-ethyl-5-(quinolin-8-yloxymeth­yl)-4H-1,2,4-triazol-3-yl]sulfan­yl}acetate

PubMed Central

Bahoussi, Rawia Imane; Djafri, Ahmed; Djafri, Ayada

2017-01-01

In the title compound, C18H20N4O3S, the 1,2,4-triazole ring is twisted with respect to the mean plane of quinoline moiety at 65.24 (4)°. In the crystal, mol­ecules are linked by weak C—H⋯O and C—H⋯N hydrogen bonds, forming the three-dimensional supra­molecular packing. π–π stacking between the quinoline ring systems of neighbouring mol­ecules is also observed, the centroid-to-centroid distance being 3.6169 (6) Å. Hirshfeld surface (HS) analyses were performed. PMID:28217336

Weak hydrogen bonding interactions influence slip system activity and compaction behavior of pharmaceutical powders.

PubMed

Khomane, Kailas S; Bansal, Arvind K

2013-12-01

Markedly different mechanical behavior of powders of polymorphs, cocrystals, hydrate/anhydrate pairs, or structurally similar molecules has been attributed to the presence of active slip planes system in their crystal structures. Presence of slip planes in the crystal lattice allows easier slip under the applied compaction pressure. This allows greater plastic deformation of the powder and results into increased interparticulate bonding area and greater tensile strength of the compacts. Thus, based on this crystallographic feature, tableting performance of the active pharmaceutical ingredients can be predicted. Recently, we encountered a case where larger numbers of CH···O type interactions across the proposed slip planes hinder the slip and thus resist plastic deformation of the powder under the applied compaction pressure. Hence, attention must be given to these types of interactions while identifying slip planes by visualization method. Generally, slip planes are visualized as flat layers often strengthened by a two-dimensional hydrogen-bonding network within the layers or planes. No hydrogen bonding should exist between these layers to consider them as slip planes. Moreover, one should also check the presence of CH···O type interactions across these planes. Mercury software provides an option for visualization of these weak hydrogen bonding interactions. Hence, caution must be exercised while selecting appropriate solid form based on this crystallographic feature. © 2013 Wiley Periodicals, Inc. and the American Pharmacists Association.

Structure of eight molecular salts assembled from noncovalent bonding between carboxylic acids, imidazole, and benzimidazole

NASA Astrophysics Data System (ADS)

Jin, Shouwen; Zhang, Huan; Liu, Hui; Wen, Xianhong; Li, Minghui; Wang, Daqi

2015-09-01

Eight organic salts of imidazole/benzimidazole have been prepared with carboxylic acids as 2-methyl-2-phenoxypropanoic acid, α-ketoglutaric acid, 5-nitrosalicylic acid, isophthalic acid, 4-nitro-phthalic acid, and 3,5-dinitrosalicylic acid. The eight crystalline forms reported are proton-transfer compounds of which the crystals and compounds were characterized by X-ray diffraction analysis, IR, mp, and elemental analysis. These structures adopted hetero supramolecular synthons, with the most common R22(7) motif observed at salts 2, 3, 5, 6 and 8. Analysis of the crystal packing of 1-8 suggests that there are extensive strong Nsbnd H⋯O, and Osbnd H⋯O hydrogen bonds (charge assisted or neutral) between acid and imidazolyl components in all of the salts. Except the classical hydrogen bonding interactions, the secondary propagating interactions also play important roles in structure extension. This variety, coupled with the varying geometries and number of acidic groups of the acids utilized, has led to the creation of eight supramolecular arrays with 1D-3D structure. The role of weak and strong noncovalent interactions in the crystal packing is analyzed. The results presented herein indicate that the strength and directionality of the Nsbnd H⋯O, and Osbnd H⋯O hydrogen bonds between acids and imidazole/benzimidazole are sufficient to bring about the formation of organic salts.

Superconductivity versus structural phase transition in the closely related Bi 2Rh 3.5S 2 and Bi 2Rh 3S 2

DOE PAGES

Kaluarachchi, Udhara S.; Xie, Weiwei; Lin, Qisheng; ...

2015-05-19

Single crystals of Bi 2Rh 3S 2 and Bi 2Rh 3.5S 2 were synthesized by solution growth, and the crystal structures and thermodynamic and transport properties of both compounds were studied. In the case of Bi 2Rh 3S 2, a structural first-order transition at around 165 K is identified by single-crystal diffraction experiments, with clear signatures visible in resistivity, magnetization, and specific heat data. No superconducting transition for Bi 2Rh 3S 2 was observed down to 0.5 K. In contrast, no structural phase transition at high temperature was observed for Bi 2Rh 3.5S 2; however, bulk superconductivity with a criticalmore » temperature, T c ≈ 1.7 K, was observed. The Sommerfeld coefficient γ and the Debye temperature (Θ D) were found to be 9.41 mJ mol –1K –2 and 209 K, respectively, for Bi 2Rh 3S 2, and 22 mJ mol –1K –2 and 196 K, respectively, for Bi 2Rh 3.5S 2. As a result, the study of the specific heat in the superconducting state of Bi 2Rh 3.5S 2 suggests that Bi 2Rh 3.5S 2 is a weakly coupled, BCS superconductor.« less

Observation of steric hindrance effect controlling crystal packing structures and physical properties in three new isomeric nitronyl nitroxide radicals

NASA Astrophysics Data System (ADS)

Zhao, Hai-Rong; Sun, Jia-Sen; Sui, Yun-Xia; Ren, Xiao-Ming; Yao, Bin-Qian; Shen, Lin-Jiang; Meng, Qing-Jin

2009-07-01

Three isomeric nitronyl nitroxide radical compounds, 2-[ n-( N-benzyl)pyridinium]-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide bromide ( n = 2, 3 and 4 for 1, 2 and 3, respectively), have been synthesized and structurally characterized. The influence of steric hindrance on the molecular packing structures and physical properties has been observed. In the radical 1, such steric hindrance leads to a folding conformation of the imidazoline and benzene rings and the intramolecular C-H…π interaction between the methyl group and the benzene ring. There is no such effect in 2 and 3. In crystal of 2, there are the intermolecular C-H…π between methyl groups and benzene ring and intermolecular π…π stacking interaction between pyridine and benzene rings. Crystal of 2 with a chiral space group P2 12 12 1 shows the SHG response about 0.4 times as that of urea. In crystal of 3, there are three symmetry-independent radical molecules, which form an unusually six-membered supramolecular ring via intermolecular O…π interactions. For the solid sample of 3, the X-band EPR exhibits an axially symmetric signal and magnetic susceptibility data suggest intermolecular antiferromagnetic (AFM) coupling interactions and very weak intermolecular ferromagnetic (FM) coupling interactions which is more likely caused by magnetic anisotropy, while measurements of both 1 and 2 show isotropic X-band EPR signals and simple Currie-Weiss magnetic behavior.

Crystal structures and Hirshfeld surface analyses of bis-[N,N-bis-(2-meth-oxy-eth-yl)di-thio-carbamato-κ2S,S']di-n-butyl-tin(IV) and [N-(2-meth-oxy-eth-yl)-N-methyl-dithio-carbamato-κ2S,S']tri-phenyl-tin(IV).

PubMed

Mohamad, Rapidah; Awang, Normah; Kamaludin, Nurul Farahana; Jotani, Mukesh M; Tiekink, Edward R T

2018-03-01

The crystal and mol-ecular structures of the two title organotin di-thio-carbamate compounds, [Sn(C 4 H 9 ) 2 (C 7 H 14 NO 2 S 2 ) 2 ], (I), and [Sn(C 6 H 5 ) 3 (C 5 H 10 NOS 2 )], (II), are described. Both structures feature asymmetrically bound di-thio-carbamate ligands leading to a skew-trapezoidal bipyramidal geometry for the metal atom in (I) and a distorted tetra-hedral geometry in (II). The complete mol-ecule of (I) is generated by a crystallographic twofold axis (Sn site symmetry 2). In the crystal of (I), mol-ecules self-assemble into a supra-molecular array parallel to (10-1) via methyl-ene-C-H⋯O(meth-oxy) inter-actions. In the crystal of (II), supra-molecular dimers are formed via pairs of weak phenyl-C-H⋯π(phen-yl) contacts. In each of (I) and (II), the specified assemblies connect into a three-dimensional architecture without directional inter-actions between them. Hirshfeld surface analyses confirm the importance of H⋯H contacts in the mol-ecular packing of each of (I) and (II), and in the case of (I), highlight the importance of short meth-oxy-H⋯H(but-yl) contacts between layers.

Investigation of intermolecular interactions in finasteride drug crystals in view of X-ray and Hirshfeld surface analysis

NASA Astrophysics Data System (ADS)

Bojarska, Joanna; Maniukiewicz, Waldemar

2015-11-01

The N,N-dimethylformamide (DMF) solvate hemihydrate (1) of finasteride, has been structurally characterized by single-crystal X-ray diffraction at 100 K and compared with previously reported finasteride crystalline forms. In addition, in order to resolve ambiguity concerning H-bond interactions, the crystal structure of finasteride hemihydrate, (2), originally reported by Schultheiss et al. in 2009, has been redetermined with higher precision. The (1) and (2) pseudopolymorphs of finasteride crystallize as orthorhombic in chiral P212121 space group with two very similar host molecules in the asymmetric unit. The conformation of fused 6-membered rings are screw-boat, chair and chair for both molecules, while 5-membered rings assume chair in (1), and half-chair in (2). There is a fairly close resemblance of the molecular geometry for all analyzed compounds, arising due to the rigid host molecule. Inter- and intramolecular host-host, host-guest strong O-H⋯O, N-H⋯O hydrogen bonds and weak C-H⋯O interactions form 3D net conferring stability to the crystal packing. Finasterides can be classified as synthon pseudopolymorphs. Isostructural solvates crystallizing in the orthorhombic space group P212121, with Z‧ = 2, exhibit R22(8) C22(15) network, monoclinic solvate (Z‧ = 1) possess D11(2), while both orthorhombic and monoclinic polymorphs have C(4) motifs, respectively. The structural similarities and subtle differences have been interpreted in view of the 3D Hirshfeld surface analysis and associated 2D fingerprint plots, which enabled detailed qualitative and quantitative insight into the intermolecular interactions. The 97-100% of Hirshfeld surface areas are due to H···H, O···H/H⋯O, C···H/H⋯C and N⋯H/H⋯N contacts. Furthermore, the electrostatic potential has been mapped over the Hirshfeld surfaces to decode the electrostatic complementarities, which exist in the crystal packing.

Structural phase transition of magnetic [Ni(dmit)2]- salts induced by supramolecular cation structures of (M+)([12]crown-4)2.

PubMed

Akutagawa, Tomoyuki; Motokizawa, Takeshi; Matsuura, Kazumasa; Nishihara, Sadafumi; Noro, Shin-ichiro; Nakamura, Takayoshi

2006-03-30

Sandwich-type supramolecular cation structures of (M(+))([12]crown-4)(2) complexes (M(+) = Li(+), Na(+), K(+), and Rb(+)) were introduced as countercations to the [Ni(dmit)(2)](-) anion, which bears an S = (1)/(2) spin, to form novel magnetic crystals (dmit(2-) = 2-thione-1,3-dithiole-4,5-dithiolate). The zigzag arrangement of Li(+)([12]crown-4)(2) cations in Li(+)([12]crown-4)(2)[Ni(dmit)(2)](-) salt induced weak intermolecular interactions of [Ni(dmit)(2)](-) dimers, whose magnetic spins were isolated from each other. The molecular arrangements of cations and anions in M(+)([12]crown-4)(2)[Ni(dmit)(2)](-) salts (M(+) = Na(+), K(+), and Rb(+)) were isostructural to each other. In the case of Na(+)([12]crown-4)(2)[Ni(dmit)(2)](-), the space group C2/m changed to C2/c with a lowering in temperature from 298 to 100 K. This structural change occurred at 222.5 K as a first-order phase transition. The space group C2/m (T = 298 K) in the salt K(+)([12]crown-4)(2)[Ni(dmit)(2)](-) also changed to C2/c (T = 100 K), which transition occurred at 270 K. Crystal structural analyses at 298 and 100 K revealed changes in both supramolecular cation conformation and [Ni(dmit)(2)](-) anion arrangements. The transition from C2/m to C2/c crystals generated a dipole moment in the Na(+)([12]crown-4)(2) and K(+)([12]crown-4)(2) structures, which were reconstructed to cancel the net dipole moment of the C2/c crystals. These cation transformations led to changes in intermolecular interactions between the [Ni(dmit)(2)](-) anions via structural rearrangements. The crystal structure of C2/c was stabilized in Rb(+)([12]crown-4)(2)[Ni(dmit)(2)](-) at 298 K. The [Ni(dmit)(2)](-) configuration in these salts with the C2/c space group was a one-dimensional uniform chain, which showed the temperature-dependent magnetic susceptibility of a one-dimensional linear Heisenberg antiferromagnetic chain.

Structure and Dynamics of Freely Suspended Liquid Crystals

NASA Technical Reports Server (NTRS)

Clark, Noel A.

2004-01-01

Smectic liquid crystals are phases of rod shaped molecules organized into one dimensionally (1 D) periodic arrays of layers, each layer being between one and two molecular lengths thick. In the least ordered smectic phases, the smectics A and C, each layer is a two dimensional (2D) liquid. Additionally there are a variety of more ordered smectic phases having hexatic short range translational order or 2D crystalline or quasi long range translational order within the layers. The inherent fluid-layer structure and low vapor pressure of smectic liquid crystals enables the long term stabilization of freely suspended, single component, layered fluid films as thin as 30A, a single molecular layer. The layering forces the films to be an integral number of smectic layers thick, quantizing their thickness in layer units and forcing a film of a particular number of layers to be physically homogeneous with respect to its layer structure over its entire area. Optical reflectivity enables the precise determination of the number of layers. These ultrathin freely suspended liquid crystal films are structures of fundamental interest in condensed matter and fluid physics. They are the thinnest known stable fluid structures and have the largest surface-to-volume ratio of any stable fluid preparation, making them ideal for the study of the effects of reduced dimensionality on phase behavior and on fluctuation and interface phenomena. Their low vapor pressure and quantized thickness enable the effective use of microgravity to extend the study of basic capillary phenomena to ultrathin fluid films. Freely suspended films have been a wellspring of new LC physics. They have been used to provide unique experimental conditions for the study of condensed phase transitions in two dimensions. They are the only system in which the hexatic has been unambiguously identified as a phase of matter, and the only physical system in which fluctuations of a 2D XY system and Kosterlitz Thouless phase transition has been observed and 2D XY quasi long range order verified. Smectic films have enabled the precise determination of smectic layer electron density and positional fluctuation profiles and have been used to show that the interlayer interactions in antiferroelectric tilted smectics do not extend significantly beyond nearest neighbors. Freely suspended films played a pivotal role in the recent discovery of macroscopic chiral-polar ordering in fluids of achiral molecules. The interactions which are operative in liquid crystals are generally weak in comparison to those in crystalline phases, leading to the facile manipulation of the order in liquid crystals by external agents such as applied fields and surfaces. Effects arising from weak ordering are significantly enhanced in ultrathin free films and filaments, in which the intermolecular coupling is effectively further reduced by loss of neighbors. Over the past four years this research, which we now detail, has produced a host of exciting new discoveries and unexpected results, maintaining the study of freely suspended liquid crystal structures as one of most exciting and fruitful areas of complex fluid physics. In addition, a class of experiments on the behavior of 1D interfaces in 2D films have been pursued with results that point to potentially quite interesting effects in microgravity.

Phonon conductivity metrics for compact, linked-cage, layered, and filled-cage crystals, using ab initio, molecular dynamics and Boltzmann transport treatments

NASA Astrophysics Data System (ADS)

Huang, Baoling

Atomic-level thermal transport in compact, layered, linked-cage, and filled-cage crystals is investigated using a multiscale approach, combines the ab initio calculation, molecular dynamics (MD), Boltzman transport equations (BTE), and the kinetic theory. These materials are of great interests in energy storage, transport, and conversion. The structural metrics of phonon conductivity of these crystals are then explored. An atomic structure-based model is developed for the understanding the relationship between the atomic structure and phonon transport in compact crystals at high temperatures. The elemental electronegativity, element mass, and the arrangement of bonds are found to be the dominant factors to determine the phonon conductivity. As an example of linked-cage crystals, the phonon conductivity of MOF-5 is investigated over a wide temperature range using MD simulations and the Green-Kubo method. The temperature dependence of the thermal conductivity of MOF-5 is found to be weak at high temperatures, which results from the suppression of the long-range acoustic phonon transport by the special linked-cage structure. The mean free path of the majority of phonons in MOF-5 is limited by the cage size. The phonon and electron transport in layered Bi2Te3 structure are investigated using the first-principle calculations, MD, and BTE. Strong anisotropy has been found for both phonon and electron transport due to the special layered structure. The long-range acoustic phonons dominate the phonon transport with a strong temperature and direction dependence. Temperature dependence of the energy gap and appropriate modelling of relaxation times are found to be important for the prediction of the electrical transport in the intrinsic regime. The scattering by the acoustic, optical, and polar-optical phonons are found to dominate the electron transport. For filled skutterudite structure, strong coupling between the filler and the host is found, which contradicts the traditional "rattler" concept. The interatomic bonds of the host are significantly affected by the filler. It is shown that without changing the interatomic potentials for the host, the filler itself can not result in a lower phonon conductivity for the filled structure. It is also found that the behavior of partially-filled skutterudites can be better understood by treating the partially-filled structure as a solid solution of the empty structure and fully-filled structure. The combination of theoretical-analysis methods used in this work, provides for comparative insight into the role of atomic structure on the phonon transport in a variety of crystals used in energy storage, transport, and conversion.

Optimal atomic structure of amorphous silicon obtained from density functional theory calculations

NASA Astrophysics Data System (ADS)

Pedersen, Andreas; Pizzagalli, Laurent; Jónsson, Hannes

2017-06-01

Atomic structure of amorphous silicon consistent with several reported experimental measurements has been obtained from annealing simulations using electron density functional theory calculations and a systematic removal of weakly bound atoms. The excess energy and density with respect to the crystal are well reproduced in addition to radial distribution function, angular distribution functions, and vibrational density of states. No atom in the optimal configuration is locally in a crystalline environment as deduced by ring analysis and common neighbor analysis, but coordination defects are present at a level of 1%-2%. The simulated samples provide structural models of this archetypal disordered covalent material without preconceived notion of the atomic ordering or fitting to experimental data.

Electronic structure of α-SrB4O7: experiment and theory

NASA Astrophysics Data System (ADS)

Atuchin, V. V.; Kesler, V. G.; Zaitsev, A. I.; Molokeev, M. S.; Aleksandrovsky, A. S.; Kuzubov, A. A.; Ignatova, N. Y.

2013-02-01

The investigation of valence band structure and electronic parameters of constituent element core levels of α-SrB4O7 has been carried out with x-ray photoemission spectroscopy. Optical-quality crystal α-SrB4O7 has been grown by the Czochralski method. Detailed photoemission spectra of the element core levels have been recorded from the powder sample under excitation by nonmonochromatic Al Kα radiation (1486.6 eV). The band structure of α-SrB4O7 has been calculated by ab initio methods and compared to XPS measurements. It has been found that the band structure of α-SrB4O7 is weakly dependent on the Sr-related states.

Microwave sol–gel synthesis and upconversion photoluminescence properties of CaGd{sub 2}(WO{sub 4}){sub 4}:Er{sup 3+}/Yb{sup 3+} phosphors with incommensurately modulated structure

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lim, Chang Sung; Aleksandrovsky, Aleksandr; Department of Photonics and Laser Technologies, Siberian Federal University, Krasnoyarsk 660079

2015-08-15

CaGd{sub 2−x}(WO{sub 4}){sub 4}:Er{sup 3+}/Yb{sup 3+} phosphors with the doping concentrations of Er{sup 3+} and Yb{sup 3+} (x=Er{sup 3+}+Yb{sup 3+}, Er{sup 3+}=0.05, 0.1, 0.2 and Yb{sup 3+}=0.2, 0.45) have been successfully synthesized by the microwave sol–gel method. The crystal structure of CaGd{sub 2−x}(WO{sub 4}){sub 4}:Er{sup 3+}/Yb{sup 3+} tungstates have been refined, and upconversion photoluminescence properties have been investigated. The synthesized particles, being formed after the heat-treatment at 900 °C for 16 h, showed a well crystallized morphology. Under the excitation at 980 nm, CaGd{sub 2}(WO{sub 4}){sub 4}:Er{sup 3+}/Yb{sup 3+} particles exhibited a strong 525-nm and a weak 550-nm emission bandsmore » in the green region and a very weak 655-nm emission band in the red region. The Raman spectrum of undoped CaGd{sub 2}(WO{sub 4}){sub 4} revealed about 12 narrow lines. The strongest band observed at 903 cm{sup −1} was assigned to the ν{sub 1} symmetric stretching vibration of WO{sub 4} tetrahedrons. The spectra of the samples doped with Er and Yb obtained under the 514.5 nm excitation were dominated by Er{sup 3+} luminescence preventing the recording of these samples Raman spectra. Concentration quenching of the erbium luminescence at {sup 2}H{sub 11/2}→{sup 4}I{sub 15/2} transition is weak in the range of erbium doping level x{sub Er}=0.05–0.2, while, for transition {sup 4}S{sub 3/2}→{sup 4}I{sub 15/2}, the signs of concentration quenching become pronounced at x{sub Er}=0.2. - Graphical abstract: CaGd{sub 2−x}(WO{sub 4}){sub 4}:Er{sup 3+}/Yb{sup 3+} phosphors with the doping concentrations of Er{sup 3+} and Yb{sup 3+} (x=Er{sup 3+}+Yb{sup 3+}, Er{sup 3+}=0.05, 0.1, 0.2 and Yb{sup 3+}=0.2, 0.45) have been successfully synthesized by the microwave sol–gel method and the crystal structure refinement, and upconversion photoluminescence properties have been investigated. - Highlights: • CaGd{sub 2−x}(WO{sub 4}){sub 4}:Er{sup 3+}/Yb{sup 3+} phosphors have been synthesized by the microwave sol–gel method. • The crystal structure of CaGd{sub 2−x}(WO{sub 4}){sub 4}:Er{sup 3+}/Yb{sup 3+} tungstates have been refined. • The upconversion photoluminescence properties have been investigated.« less

Magnetic behavior and spin-lattice coupling in cleavable van der Waals layered CrCl 3 crystals

DOE PAGES

McGuire, Michael A.; Clark, Genevieve; KC, Santosh; ...

2017-06-19

CrCl 3 is a layered insulator that undergoes a crystallographic phase transition below room temperature and orders antiferromagnetically at low temperature. Weak van der Waals bonding between the layers and ferromagnetic in-plane magnetic order make it a promising material for obtaining atomically thin magnets and creating van der Waals heterostructures. In this work we have grown crystals of CrCl 3, revisited the structural and thermodynamic properties of the bulk material, and explored mechanical exfoliation of the crystals. We find two distinct anomalies in the heat capacity at 14 and 17 K confirming that the magnetic order develops in two stagesmore » on cooling, with ferromagnetic correlations forming before long-range antiferromagnetic order develops between them. This scenario is supported by magnetization data. A magnetic phase diagram is constructed from the heat capacity and magnetization results. We also find an anomaly in the magnetic susceptibility at the crystallographic phase transition, indicating some coupling between the magnetism and the lattice. First-principles calculations accounting for van der Waals interactions also indicate spin-lattice coupling, and find multiple nearly degenerate crystallographic and magnetic structures consistent with the experimental observations. Lastly, we demonstrate that monolayer and few-layer CrCl 3 specimens can be produced from the bulk crystals by exfoliation, providing a path for the study of heterostructures and magnetism in ultrathin crystals down to the monolayer limit.« less

Magnetic behavior and spin-lattice coupling in cleavable van der Waals layered CrCl 3 crystals

DOE Office of Scientific and Technical Information (OSTI.GOV)

McGuire, Michael A.; Clark, Genevieve; KC, Santosh

CrCl 3 is a layered insulator that undergoes a crystallographic phase transition below room temperature and orders antiferromagnetically at low temperature. Weak van der Waals bonding between the layers and ferromagnetic in-plane magnetic order make it a promising material for obtaining atomically thin magnets and creating van der Waals heterostructures. In this work we have grown crystals of CrCl 3, revisited the structural and thermodynamic properties of the bulk material, and explored mechanical exfoliation of the crystals. We find two distinct anomalies in the heat capacity at 14 and 17 K confirming that the magnetic order develops in two stagesmore » on cooling, with ferromagnetic correlations forming before long-range antiferromagnetic order develops between them. This scenario is supported by magnetization data. A magnetic phase diagram is constructed from the heat capacity and magnetization results. We also find an anomaly in the magnetic susceptibility at the crystallographic phase transition, indicating some coupling between the magnetism and the lattice. First-principles calculations accounting for van der Waals interactions also indicate spin-lattice coupling, and find multiple nearly degenerate crystallographic and magnetic structures consistent with the experimental observations. Lastly, we demonstrate that monolayer and few-layer CrCl 3 specimens can be produced from the bulk crystals by exfoliation, providing a path for the study of heterostructures and magnetism in ultrathin crystals down to the monolayer limit.« less

Synthesis, crystal structure, spectroscopic characterization, docking simulation and density functional studies of 1-(3,4-dimethoxyphenyl) -3-(4-flurophenyl)-propan-1-one

NASA Astrophysics Data System (ADS)

Khamees, Hussien Ahmed; Jyothi, Mahima; Khanum, Shaukath Ara; Madegowda, Mahendra

2018-06-01

The compound 1-(3,4-dimethoxyphenyl)-3-(4-flurophenyl)-propan-1-one (DFPO) was synthesized by Claisen-Schmidt condensation reaction and the single crystals were obtained by slow evaporation method. Three-dimensional structure was confirmed by single crystal X-ray diffraction method and exhibiting the triclinic crystal system with space group P-1. The crystal structure is stabilized by Csbnd H⋯O intermolecular and weak interactions. Computed molecular geometry has been obtained by density functional theory (DFT) and compared with experimental results. The spectra of both FT-IR in the range (4000-400 cm-1) and FT- Raman (3500-50 cm-1) of DFPO were recorded experimentally and computed by (DFT) using B3LYP/6-311G (d,p) as basis sets. Intramolecular charge transfer has been scanned using natural bond orbital (NBO) analysis and revealed the various contribution of bonding and lone pair to the stabilization of molecule. Nonlinear optical activity (NLO) of the title compound has been determined by second harmonic generation (SHG) and computed using DFT method. Hyperpolarizability, HOMO-LUMO energy gap, hardness, softness electronegativity and others Global reactivity descriptors of DFPO has been calculated and revealed complete picture of chemical reactivity of DFPO. Hirshfeld surface analyses were applied to investigate the intermolecular interactions and revealed that more than two-thirds of the inter contacts are associated with O⋯H, C⋯H and H⋯H interactions. Docking studies of DFPO showed inhibition of Vascular endothelial growth Factor human receptor (VEGFR-2) signalling pathway, which indicates DFPO as anti-angiogenesis, that play pivotal role in cancer, so we suggest it for clinical studies to evaluate its potential to treat human cancers.

Structure characterization, photoluminescence and dielectric properties of a new hybrid compound containing chlorate anions of zincate (II)

NASA Astrophysics Data System (ADS)

Lassoued, Mohamed Saber; Abdelbaky, Mohammed S. M.; Ben Soltan, Wissem; Lassoued, Abdelmajid; Ammar, Salah; Gadri, Abdellatif; Ben Salah, Abdelhamid; García-Granda, Santiago

2018-04-01

A new hybrid compound, bis (2-aminophenylenamonium) tetrachlorozincate (II), was synthesized and formulated as (C6H9N2)2ZnCl4. Its crystal structure was solved by single crystal X-ray diffraction reveling that compound crystallizes in the monoclinic system, space group C2/c (N°: 15) with cell parameters a = 7.4957(4) Å, b = 25.6837(15) Å, c = 9.4041(5) Å, β = 94.35(0)°, V = 1805.23(45) Å3. Their atomic arrangement can be described as an alternation of inorganic and organic layers, [ZnCl4]2- tetrahedral anions and 2-aminophenylenamonium cations. The cohesion of the atomic arrangement is ensured by hydrogen bonds (strong Nsbnd H⋯N and weak Nsbnd H⋯Cl) and π-π stacking interactions between identical antiparallel organic moieties. In optical transmission and photoluminescence measurements, this material exhibit two absorption bands (253 and 316 nm) and a strong emission line (390 nm), while the thermal analysis disclosed a phase transition at 420-445 K previously to the sample decomposition at 476 K. Finally, electrical measurements were performed to discuss the phase-transition mechanism.

Crystal structure of an unknown tetra­hydro­furan solvate of tetra­kis­(μ 3-cyanato-κ3 N:N:N)tetra­kis­[(triphenyl­phosphane-κP)­silver(I)

PubMed Central

Frenzel, Peter; Schaarschmidt, Dieter; Jakob, Alexander; Lang, Heinrich

2015-01-01

In the title compound, [{[(C6H5)3P]Ag}4{NCO}4], a distorted Ag4N4-heterocubane core is set up by four AgI ions being coordinated by the N atoms of the cyanato anions in a μ 3-bridging mode. In addition, a tri­phenyl­phosphine ligand is datively bonded to each of the AgI ions. Intra­molecular Ag⋯Ag distances as short as 3.133 (9) Å suggest the presence of argentophilic (d 10⋯d 10) inter­actions. Five moderate-to-weak C—H⋯O hydrogen-bonding inter­actions are observed in the crystal structure, spanning a three-dimensional network. A region of electron density was treated with the SQUEEZE procedure in PLATON [Spek (2015). Acta Cryst. C71, 9–18] following unsuccessful attempts to model it as being part of disordered tetra­hydro­furan solvent mol­ecules. The given chemical formula and other crystal data do not take into account these solvent mol­ecules. PMID:26594421

Application of London-type dispersion corrections to the solid-state density functional theory simulation of the terahertz spectra of crystalline pharmaceuticals.

PubMed

King, Matthew D; Buchanan, William D; Korter, Timothy M

2011-03-14

The effects of applying an empirical dispersion correction to solid-state density functional theory methods were evaluated in the simulation of the crystal structure and low-frequency (10 to 90 cm(-1)) terahertz spectrum of the non-steroidal anti-inflammatory drug, naproxen. The naproxen molecular crystal is bound largely by weak London force interactions, as well as by more prominent interactions such as hydrogen bonding, and thus serves as a good model for the assessment of the pair-wise dispersion correction term in systems influenced by intermolecular interactions of various strengths. Modifications to the dispersion parameters were tested in both fully optimized unit cell dimensions and those determined by X-ray crystallography, with subsequent simulations of the THz spectrum being performed. Use of the unmodified PBE density functional leads to an unrealistic expansion of the unit cell volume and the poor representation of the THz spectrum. Inclusion of a modified dispersion correction enabled a high-quality simulation of the THz spectrum and crystal structure of naproxen to be achieved without the need for artificially constraining the unit cell dimensions.

Measurement-device-independent quantum key distribution with multiple crystal heralded source with post-selection

NASA Astrophysics Data System (ADS)

Chen, Dong; Shang-Hong, Zhao; MengYi, Deng

2018-03-01

The multiple crystal heralded source with post-selection (MHPS), originally introduced to improve the single-photon character of the heralded source, has specific applications for quantum information protocols. In this paper, by combining decoy-state measurement-device-independent quantum key distribution (MDI-QKD) with spontaneous parametric downconversion process, we present a modified MDI-QKD scheme with MHPS where two architectures are proposed corresponding to symmetric scheme and asymmetric scheme. The symmetric scheme, which linked by photon switches in a log-tree structure, is adopted to overcome the limitation of the current low efficiency of m-to-1 optical switches. The asymmetric scheme, which shows a chained structure, is used to cope with the scalability issue with increase in the number of crystals suffered in symmetric scheme. The numerical simulations show that our modified scheme has apparent advances both in transmission distance and key generation rate compared to the original MDI-QKD with weak coherent source and traditional heralded source with post-selection. Furthermore, the recent advances in integrated photonics suggest that if built into a single chip, the MHPS might be a practical alternative source in quantum key distribution tasks requiring single photons to work.

Supramolecular engineering of carbon nanostructures

NASA Astrophysics Data System (ADS)

Jian, Kengqing

This thesis identifies a new and flexible route to control graphene layer structure in carbons, which is the key to carbon properties and applications, and focuses on the synthesis, structure-property relationships, and potential applications of new "supramolecular" carbon nanomaterials. This new approach begins with the studies of surface anchoring and assembly mechanisms among planar discotic liquid crystals. The results show that disk-like polyaromatics exhibit weak noncovalent interactions with most surfaces and prefer edge-on anchoring at these surfaces; only on a few surfaces such as graphite and platinum, they prefer face-on anchoring. A theory of pi-pi bond preservation has been proposed to explain the wetting, anchoring, and assembly phenomena. Based on the assembly study, a supramolecular approach was developed, which uses surfaces, flows, and confinement to create well-defined order in discotic liquid crystals, which can then be covalently captured by cross-linking and converted into a carbon material whose structure is an accurate replica of the molecular order in the precursor. This technique has been successfully applied to create innovative nanocarbons with controllable nanostructures. The new nanomaterials synthesized by supramolecular route include organic and carbon films with precise crystal structure control using surface anchoring and flow. Lithographic techniques were employed to make micro-patterned surfaces with preprogrammed molecular orientations. Fully dense and ordered carbon thin films were prepared from lytropic liquid crystals. These films exhibit surfaces rich in edge-sites and are either anisotropic unidirectional or multi-domain. In addition, four different types of high-aspect-ratio nanocarbons were synthesized and analyzed: (1) "orthogonal" carbon nanofibers with perpendicular graphene layers, (2) "concentric" C/C-composite nanofibers with graphene layers parallel to the fiber axis, (3) "inverted" nanotubes exhibiting graphene edge planes at both inner and outer surfaces, and (4) nanoribbons. Finally, a set of mesoporous carbons were synthesized with both porous structure and interfacial structure systematically controlled by liquid crystal templating. A quantitative model was developed for carbon surface area prediction. In addition to synthesis, this thesis includes extensive structural analysis and some surface characterization of these nanomaterials, and offers ideas to exploit their unique properties for applications in composites, displays, nanomedicine, and the environment.

3-(2-Bromo-4,5-dimethoxy­phen­yl)propiononitrile

PubMed Central

Liu, Yan-Ping; Wang, De-Cai; Chen, Hui; Kang, Si-Shun; Huang, Xin-Ming

2008-01-01

In the mol­ecule of the title compound, C11H12BrNO2, a weak intra­molecular C—H⋯Br hydrogen bond results in the formation of a five-membered ring, which adopts an envelope conformation with the H atom displaced by 0.486 Å from the plane of the other ring atoms. In the crystal structure, inter­molecular C—H⋯O hydrogen bonds link the mol­ecules. PMID:21202583

1,5-Bis[(E)-cyclo­pentyl­idene]thio­carbono­hydrazide

PubMed Central

Guo, Qingliang; Sun, Junshan; Li, Jikun; Wu, Rentao; Duan, Wenzeng

2009-01-01

In the title mol­ecule, C11H18N4S, an intra­molecular N—H⋯N hydrogen bond [N⋯N = 2.558 (3)Å] is observed. The two cyclo­pentyl rings are disordered between two conformations in 1:1 and 2:1 ratios. In the crystal structure, weak inter­molecular N—H⋯S hydrogen bonds [N⋯S = 3.547 (3) Å] link pairs of mol­ecules into centrosymmetric dimers. PMID:21582539

Propyl 3-oxo-2,3-dihydro-1,2-benzothia­zole-2-carboxyl­ate

PubMed Central

Wang, Xiang-hui; Yang, Jian-xin; You, Cheng-hang; Lin, Qiang

2011-01-01

The title compound, C11H11NO3S, was synthesized by the reaction of benzo[d]isothia­zol-3(2H)-one with propyl carbono­chloridate in toluene. The benzoisothiazolone ring system is approximately planar with a maximum deviation from the mean plane of 0.0226 (14) Å for the N atom. Weak inter­molecular C—H⋯O hydrogen bonding occurs in the crystal structure. PMID:22065833

[Ni(cod) 2][Al(OR F) 4], a Source for Naked Nickel(I) Chemistry

DOE Office of Scientific and Technical Information (OSTI.GOV)

Schwab, Miriam M.; Himmel, Daniel; Kacprzak, Sylwia

The straightforward synthesis of the cationic, purely organometallic Ni I salt [Ni(cod) 2] +[Al(OR F) 4] - was realized through a reaction between [Ni(cod) 2] and Ag[Al(OR F) 4] (cod=1,5-cyclooctadiene). Crystal-structure analysis and EPR, XANES, and cyclic voltammetry studies confirmed the presence of a homoleptic NiI olefin complex. Weak interactions between the metal center, the ligands, and the anion provide a good starting material for further cationic NiI complexes.

Weak ferromagnetism along the third-order axis of the FeBO3 crystals caused by Fe2+ impurity ions

NASA Astrophysics Data System (ADS)

Ovchinnikov, S. G.; Rudenko, V. V.; Vorotynov, A. M.

2018-05-01

Using the single-ion approximation, the weak ferromagnetic moment σZ(Fe2+) along the third-order axis of FeBO3 crystals, which is caused by the contribution of Fe2+ ions, has been investigated in the framework of the model Fe2+ impurity ion -BO3 vacancy. The extreme low-temperature behavior of the total magnetic moment due to the strong dependence of the Fe2+ion contribution is predicted.

Low cost solution-based materials processing methods for large area OLEDs and OFETs

NASA Astrophysics Data System (ADS)

Jeong, Jonghwa

In Part 1, we demonstrate the fabrication of organic light-emitting devices (OLEDs) with precisely patterned pixels by the spin-casting of Alq3 and rubrene thin films with dimensions as small as 10 mum. The solution-based patterning technique produces pixels via the segregation of organic molecules into microfabricated channels or wells. Segregation is controlled by a combination of weak adsorbing characteristics of aliphatic terminated self-assembled monolayers (SAMs) and by centrifugal force, which directs the organic solution into the channel or well. This novel patterning technique may resolve the limitations of pixel resolution in the method of thermal evaporation using shadow masks, and is applicable to the fabrication of large area displays. Furthermore, the patterning technique has the potential to produce pixel sizes down to the limitation of photolithography and micromachining techniques, thereby enabling the fabrication of high-resolution microdisplays. The patterned OLEDs, based upon a confined structure with low refractive index of SiO2, exhibited higher current density than an unpatterned OLED, which results in higher electroluminescence intensity and eventually more efficient device operation at low applied voltages. We discuss the patterning method and device fabrication, and characterize the morphological, optical, and electrical properties of the organic pixels. In part 2, we demonstrate a new growth technique for organic single crystals based on solvent vapor assisted recrystallization. We show that, by controlling the polarity of the solvent vapor and the exposure time in a closed system, we obtain rubrene in orthorhombic to monoclinic crystal structures. This novel technique for growing single crystals can induce phase shifting and alteration of crystal structure and lattice parameters. The organic molecules showed structural change from orthorhombic to monoclinic, which also provided additional optical transition of hypsochromic shift from that of the orthorhombic form. An intermediate form of the crystal exhibits an optical transition to the lowest vibrational energy level that is otherwise disallowed in the single-crystal orthorhombic form. The monoclinic form exhibits entirely new optical transitions and showed a possible structural rearrangement for increasing charge carrier mobility, making it promising for organic devices. These phenomena can be explained and proved by the chemical structure and molecular packing of the monoclinic form, transformed from orthorhombic crystalline structure.

Crystal structure and functional characterization of yeast YLR011wp, an enzyme with NAD(P)H-FMN and ferric iron reductase activities.

PubMed

Liger, Dominique; Graille, Marc; Zhou, Cong-Zhao; Leulliot, Nicolas; Quevillon-Cheruel, Sophie; Blondeau, Karine; Janin, Joël; van Tilbeurgh, Herman

2004-08-13

Flavodoxins are involved in a variety of electron transfer reactions that are essential for life. Although FMN-binding proteins are well characterized in prokaryotic organisms, information is scarce for eukaryotic flavodoxins. We describe the 2.0-A resolution crystal structure of the Saccharomyces cerevisiae YLR011w gene product, a predicted flavoprotein. YLR011wp indeed adopts a flavodoxin fold, binds the FMN cofactor, and self-associates as a homodimer. Despite the absence of the flavodoxin key fingerprint motif involved in FMN binding, YLR011wp binds this cofactor in a manner very analogous to classical flavodoxins. YLR011wp closest structural homologue is the homodimeric Bacillus subtilis Yhda protein (25% sequence identity) whose homodimer perfectly superimposes onto the YLR011wp one. Yhda, whose function is not documented, has 53% sequence identity with the Bacillus sp. OY1-2 azoreductase. We show that YLR011wp has an NAD(P)H-dependent FMN reductase and a strong ferricyanide reductase activity. We further demonstrate a weak but specific reductive activity on azo dyes and nitrocompounds.

Polyacrylonitrile nanofiber as polar solvent N,N-dimethyl formamide sensor based on quartz crystal microbalance technique

NASA Astrophysics Data System (ADS)

Rianjanu, A.; Julian, T.; Hidayat, S. N.; Suyono, E. A.; Kusumaatmaja, A.; Triyana, K.

2018-04-01

Here, we describe an N,N-dimethyl formamide (DMF) vapour sensor fabricated by coating polyacrylonitrile (PAN) nanofiber structured on quartz crystal microbalance (QCM). The PAN nanofiber sensors with an average diameter of 225 nm to 310 nm were fabricated via electrospinning process with different mass deposition on QCM substrate. The nanostructured of PAN nanofiber offers a high specific surface area that improved the sensing performance of nanofiber sensors. Benefiting from that fine structure, and high polymer-solvent affinity between PAN and DMF, the development of DMF sensors presented good response at ambient temperature. Since there is no chemical reaction between PAN nanofiber and DMF vapour, weak physical interaction such absorption and swelling were responsible for the sensing behavior. The results are indicating that the response of PAN nanofiber sensors has more dependency on the nanofiber structure (specific surface area) rather than its mass deposition. The sensor also showed good stability after a few days sensing. These findings have significant implications for developing DMF vapour sensor based on QCM coated polymer nanofibers.

Crystallographic Study of a Novel Sub-Nanomolar Inhibitor Provides Insight on the Binding Interactions of Alkenyldiarylmethanes with Human Immunodeficiency Virus-1 (HIV-1) Reverse Transcriptase†

PubMed Central

Cullen, Matthew D.; Ho, William C.; Bauman, Joseph D.; Das, Kalyan; Arnold, Eddy; Hartman, Tracy L.; Watson, Karen M.; Buckheit, Robert W.; Pannecouque, Christophe; De Clercq, Erik; Cushman, Mark

2009-01-01

Two crystal structures have been solved for separate complexes of alkenyldiarylmethane (ADAM) non-nucleoside reverse transcriptase inhibitors (NNRTI) 3 and 4 with HIV-1 reverse transcriptase (RT). The structures reveal inhibitor binding is exclusively hydrophobic in nature and the shape of the inhibitor-bound NNRTI binding pocket is unique among other reported inhibitor-RT crystal structures. Primarily, ADAMs 3 and 4 protrude from a large gap in the backside of the binding pocket, placing portions of the inhibitors unusually close to the polymerase active site and allowing 3 to form a weak hydrogen bond with Lys223. The lack of additional stabilizing interactions, beyond the observed hydrophobic surface contacts, between 4 and RT is quite perplexing given the extreme potency of the compound (IC50 ≤ nM). ADAM 4 was designed to be hydrolytically stable in blood plasma, and an investigation of its hydrolysis in rat plasma demonstrated it has a significantly prolonged half-life in comparison to ADAM lead compounds 1 and 2. PMID:19775161

Transmission properties of one-dimensional ternary plasma photonic crystals

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shiveshwari, Laxmi; Awasthi, S. K.

2015-09-15

Omnidirectional photonic band gaps (PBGs) are found in one-dimensional ternary plasma photonic crystals (PPC) composed of single negative metamaterials. The band characteristics and transmission properties are investigated through the transfer matrix method. We show that the proposed structure can trap light in three-dimensional space due to the elimination of Brewster's angle transmission resonance allowing the existence of complete PBG. The results are discussed in terms of incident angle, layer thickness, dielectric constant of the dielectric material, and number of unit cells (N) for TE and TM polarizations. It is seen that PBG characteristics is apparent even in an N ≥ 2 system,more » which is weakly sensitive to the incident angle and completely insensitive to the polarization. Finite PPC could be used for multichannel transmission filter without introducing any defect in the geometry. We show that the locations of the multichannel transmission peaks are in the allowed band of the infinite structure. The structure can work as a single or multichannel filter by varying the number of unit cells. Binary PPC can also work as a polarization sensitive tunable filter.« less

Movie of the structural changes during a catalytic cycle of nucleoside monophosphate kinases.

PubMed

Vonrhein, C; Schlauderer, G J; Schulz, G E

1995-05-15

There are 17 crystal structures of nucleoside monophosphate kinases known. As expected for kinases, they show large conformational changes upon binding of substrates. These are concentrated in two chain segments, or domains, of 30 and 38 residues that are involved in binding of the substrates N1TP and N2MP (nucleoside tri- and monophosphates with bases N1 and N2), respectively. After aligning the 17 structures on the main parts of their polypeptide chains, two domains in various conformational states were revealed. These states were caused by bound substrate (or analogues) and by crystal-packing forces, and ranged between a 'closed' conformation and a less well defined 'open' conformation. The structures were visually sorted yielding an approximately evenly spaced series of domain states that outlines the closing motions when the substrates bind. The packing forces in the crystals are weak, leaving the natural domain trajectories essentially intact. Packing is necessary, however, to produce stable intermediates. The ordered experimental structures were then recorded as still pictures of a movie and animated to represent the motions of the molecule during a catalytic cycle. The motions were smoothed out by adding interpolated structures to the observed ones. The resulting movies are available through the World Wide Web (http:@bio5.chemie.uni-freiburg.de/ak movie.html). Given the proliferating number of homologous proteins known to exist in different conformational states, it is becoming possible to outline the motions of chain segments and combine them into a movie, which can then represent protein action much more effectively than static pictures alone are able to do.

Unconventional Superconductivity in Luttinger Semimetals: Theory of Complex Tensor Order and the Emergence of the Uniaxial Nematic State

NASA Astrophysics Data System (ADS)

Boettcher, Igor; Herbut, Igor F.

2018-02-01

We investigate unconventional superconductivity in three-dimensional electronic systems with the chemical potential close to a quadratic band touching point in the band dispersion. Short-range interactions can lead to d -wave superconductivity, described by a complex tensor order parameter. We elucidate the general structure of the corresponding Ginzburg-Landau free energy and apply these concepts to the case of an isotropic band touching point. For a vanishing chemical potential, the ground state of the system is given by the superconductor analogue of the uniaxial nematic state, which features line nodes in the excitation spectrum of quasiparticles. In contrast to the theory of real tensor order in liquid crystals, however, the ground state is selected here by the sextic terms in the free energy. At a finite chemical potential, the nematic state has an additional instability at weak coupling and low temperatures. In particular, the one-loop coefficients in the free energy indicate that at weak coupling genuinely complex orders, which break time-reversal symmetry, are energetically favored. We relate our analysis to recent measurements in the half-Heusler compound YPtBi and discuss the role of cubic crystal symmetry.

Reflective-emissive liquid-crystal displays constructed from AIE luminogens (Presentation Recording)

NASA Astrophysics Data System (ADS)

Tang, Ben Zhong; Zhao, Dongyu; Qin, Anjun

2015-10-01

The chiral nematic liquid crystal (N*-LC) has plenty of prospective applications in LC display (LCD) owing to the selective reflection and circular dichroism. The molecules in the N*-LC are aligned forming a helically twisted structure and the specific wavelength of incident light is reflected by the periodically varying refractive index in the N*-LC plane without the aid of a polarizer or color filter. However, N*-LC do not emit light which restricts its application in the dark environment. Moreover, the view angle of N*-LC display device was severe limited due to the strong viewing angle dependence of the structure color of the one dimensional photonic crystal of a N*-LC. In order to overcome these weaknesses, we have synthesized a luminescent liquid crystalline compound consisting of a tetraphenylethene (TPE) core, TPE-PPE, as a luminogen with mesogenic moieties. TPE-PPE exhibits both the aggregate-induced emission (AIE) and thermotropic liquid crystalline characteristics. By dissolving a little amount of TPE-PPE into N*-LC host, a circular polarized emission was obtained on the unidirectional orientated LC cell. Utilizing the circular polarized luminescence property of the LC mixture, we fabricated a photoluminescent liquid crystal display (PL-LCD) device which can work under both dark and sunlit conditions. This approach has simplified the device design, lowered the energy consumption and increased brightness and application of the LCD.

Structural transition and orbital glass physics in near-itinerant CoV 2O 4

DOE Office of Scientific and Technical Information (OSTI.GOV)

Reig-i-Plessis, D.; Casavant, D.; Garlea, Vasile O.

2016-01-25

In this study, the ferrimagnetic spinel CoV 2O 4 has been a topic of intense recent interest, both as a frustrated insulator with unquenched orbital degeneracy and as a near-itinerant magnet which can be driven metallic with moderate applied pressure. Here, we report on our recent neutron di raction and inelastic scattering measurements on powders with minimal cation site disorder. Our main new result is the identification of a weak (Δa/a ~ 10 –4), first order structural phase transition at T* = 90 K, the same temperature where spin canting was seen in recent single crystal measurements. This transition ismore » characterized by a short-range distortion of oxygen octahedral positions, and inelastic data further establish a weak 1.25meV spin gap at low temperature. Together, these findings provide strong support for the local orbital picture and the existence of an orbital glass state at temperatures below T*.« less

Surface Composition of NiPd Alloys

NASA Technical Reports Server (NTRS)

Noebe, Ronald D.; Khalil, Joe; Bozzolo, Guillermo; Gray, Hugh R. (Technical Monitor)

2002-01-01

Surface segregation in Ni-Pd alloys has been studied using the BFS method for alloys. Not only does the method predict an oscillatory segregation profile but it also indicates that the number of Pd-enriched surface planes can vary as a function of orientation. The segregation profiles were computed as a function of temperature, crystal face, and composition. Pd enrichment of the first layer is observed in (111) and (100) surfaces, and enrichment of the top two layers occurs for (110) surfaces. In all cases, the segregation profile shows oscillations that are actually related to weak ordering tendencies in the bulk. An atom-by-atom analysis was performed to identify the competing mechanisms leading to the observed surface behaviors. Large-scale atomistic simulations were also performed to investigate the temperature dependence of the segregation profiles as well as for analysis of the bulk structures. Finally, the observed surface behaviors are discussed in relation to the bulk phase structure of Ni-Pd alloys, which exhibit a tendency to weakly order.

Multiple diffraction in an icosahedral Al-Cu-Fe quasicrystal

NASA Astrophysics Data System (ADS)

Fan, C. Z.; Weber, Th.; Deloudi, S.; Steurer, W.

2011-07-01

In order to reveal its influence on quasicrystal structure analysis, multiple diffraction (MD) effects in an icosahedral Al-Cu-Fe quasicrystal have been investigated in-house on an Oxford Diffraction four-circle diffractometer equipped with an Onyx™ CCD area detector and MoKα radiation. For that purpose, an automated approach for Renninger scans (ψ-scans) has been developed. Two weak reflections were chosen as the main reflections (called P) in the present measurements. As is well known for periodic crystals, it is also observed for this quasicrystal that the intensity of the main reflection may significantly increase if the simultaneous (H) and the coupling (P-H) reflections are both strong, while there is no obvious MD effect if one of them is weak. The occurrence of MD events during ψ-scans has been studied based on an ideal structure model and the kinematical MD theory. The reliability of the approach is revealed by the good agreement between simulation and experiment. It shows that the multiple diffraction effect is quite significant.

Mechanism of partial agonism in AMPA-type glutamate receptors

PubMed Central

Salazar, Hector; Eibl, Clarissa; Chebli, Miriam; Plested, Andrew

2017-01-01

Neurotransmitters trigger synaptic currents by activating ligand-gated ion channel receptors. Whereas most neurotransmitters are efficacious agonists, molecules that activate receptors more weakly—partial agonists—also exist. Whether these partial agonists have weak activity because they stabilize less active forms, sustain active states for a lesser fraction of the time or both, remains an open question. Here we describe the crystal structure of an α-amino-3-hydroxy-5-methyl-4-isoxazolepropionate receptor (AMPAR) ligand binding domain (LBD) tetramer in complex with the partial agonist 5-fluorowillardiine (FW). We validate this structure, and others of different geometry, using engineered intersubunit bridges. We establish an inverse relation between the efficacy of an agonist and its promiscuity to drive the LBD layer into different conformations. These results suggest that partial agonists of the AMPAR are weak activators of the receptor because they stabilize multiple non-conducting conformations, indicating that agonism is a function of both the space and time domains. PMID:28211453

Bioactive compounds from Stuhlmannia moavi from the Madagascar dry forest.

PubMed

Liu, Yixi; Harinantenaina, Liva; Brodie, Peggy J; Bowman, Jessica D; Cassera, Maria B; Slebodnick, Carla; Callmander, Martin W; Randrianaivo, Richard; Rakotobe, Etienne; Rasamison, Vincent E; Applequist, Wendy; Birkinshaw, Chris; Lewis, Gwilym P; Kingston, David G I

2013-12-15

Bioassay-directed fractionation of the leaf and root extracts of the antiproliferative Madagascar plant Stuhlmannia moavi afforded 6-acetyl-5,8-dihydroxy-2-methoxy-7-methyl-1,4-naphthoquinone (stuhlmoavin, 1) as the most active compound, with an IC50 value of 8.1 μM against the A2780 human ovarian cancer cell line, as well as the known homoisoflavonoid bonducellin (2) and the stilbenoids 3,4,5'-trihydroxy-3'-methoxy-trans-stilbene (3), piceatannol (4), resveratrol (5), rhapontigenin (6), and isorhapontigenin (7). The structure elucidation of all compounds was based on NMR and mass spectroscopic data, and the structure of 1 was confirmed by a single crystal X-ray analysis. Compounds 2-5 showed weak A2780 activities, with IC50 values of 10.6, 54.0, 41.0, and 74.0 μM, respectively. Compounds 1-3 also showed weak antimalarial activity against Plasmodium falciparum with IC50 values of 23, 26, and 27 μM, respectively. Copyright © 2013 Elsevier Ltd. All rights reserved.

Neutron powder diffraction study on the iron-based nitride superconductor ThFeAsN

NASA Astrophysics Data System (ADS)

Mao, Huican; Wang, Cao; Maynard-Casely, Helen E.; Huang, Qingzhen; Wang, Zhicheng; Cao, Guanghan; Li, Shiliang; Luo, Huiqian

2017-03-01

We report neutron diffraction and transport results on the newly discovered superconducting nitride ThFeAsN with T_c= 30 \\text{K} . No magnetic transition, but a weak structural distortion around 160 K, is observed by cooling from 300 K to 6 K. Analysis on the resistivity, Hall transport and crystal structure suggests that this material behaves as an electron optimally doped pnictide superconductor due to extra electrons from nitrogen deficiency or oxygen occupancy at the nitrogen site, which, together with the low arsenic height, may enhance the electron itinerancy and reduce the electron correlations, thus suppressing the static magnetic order.

Fully gapped superconductivity in single crystals of noncentrosymmetric Re6Zr with broken time-reversal symmetry

NASA Astrophysics Data System (ADS)

Pang, G. M.; Nie, Z. Y.; Wang, A.; Singh, D.; Xie, W.; Jiang, W. B.; Chen, Y.; Singh, R. P.; Smidman, M.; Yuan, H. Q.

2018-06-01

The noncentrosymmetric superconductor Re6Zr has attracted much interest due to the observation of broken time-reversal symmetry in the superconducting state. Here we report an investigation of the superconducting gap structure of Re6Zr single crystals by measuring the magnetic penetration depth shift Δ λ (T ) and electronic specific heat Ce(T ) . Δ λ (T ) exhibits an exponential temperature dependence behavior for T ≪Tc , which indicates a fully open superconducting gap. Our analysis shows that a single gap s -wave model is sufficient to describe both the superfluid density ρs(T ) and Ce(T ) results, with a fitted gap magnitude larger than the weak coupling BCS value, providing evidence for fully gapped superconductivity in Re6Zr with moderate coupling.

Dimethyl 4-[3-(4-meth­oxy­phen­yl)-1-phenyl-1H-pyrazol-4-yl]-2,6-dimethyl-1,4-dihydro­pyridine-3,5-dicarboxyl­ate dihydrate

PubMed Central

Fun, Hoong-Kun; Ooi, Chin Wei; Garudachari, B.; Shivananda, Kammasandra Nanjunda; Isloor, Arun M.

2012-01-01

In the title compound, C27H27N3O5·2H2O, the dihydro­pyridine ring adopts a flattened boat conformation. The central pyrazole ring is essentially planar [maximum deviation of 0.003 (1) Å] and makes dihedral angles of 50.42 (6) and 26.44 (6)° with the benzene rings. In the crystal, mol­ecules are linked via N—H⋯O, O—H⋯O, O—H⋯N and C—H⋯O hydrogen bonds into two-dimensional networks parallel to the bc plane. The crystal structure is further consolidated by weak C—H⋯π inter­actions. PMID:22798871

Noncollinear antiferromagnetic Mn3Sn films

NASA Astrophysics Data System (ADS)

Markou, A.; Taylor, J. M.; Kalache, A.; Werner, P.; Parkin, S. S. P.; Felser, C.

2018-05-01

Noncollinear hexagonal antiferromagnets with almost zero net magnetization were recently shown to demonstrate giant anomalous Hall effect. Here, we present the structural and magnetic properties of noncollinear antiferromagnetic Mn3Sn thin films heteroepitaxially grown on Y:ZrO2 (111) substrates with a Ru underlayer. The Mn3Sn films were crystallized in the hexagonal D 019 structure with c -axis preferred (0001) crystal orientation. The Mn3Sn films are discontinuous, forming large islands of approximately 400 nm in width, but are chemical homogeneous and characterized by near perfect heteroepitaxy. Furthermore, the thin films show weak ferromagnetism with an in-plane uncompensated magnetization of M =34 kA/m and coercivity of μ0Hc=4.0 mT at room temperature. Additionally, the exchange bias effect was studied in Mn3Sn /Py bilayers. Exchange bias fields up to μ0HEB=12.6 mT can be achieved at 5 K. These results show Mn3Sn films to be an attractive material for applications in antiferromagnetic spintronics.

Crystal structure of 1-(8-meth-oxy-2H-chromen-3-yl)ethanone.

PubMed

Koh, Dongsoo

2014-09-01

In the structure of the title compound, C12H12O3, the di-hydro-pyran ring is fused with the benzene ring. The di-hydro-pyran ring is in a half-chair conformation, with the ring O and methyl-ene C atoms positioned 1.367 (3) and 1.504 (4) Å, respectively, on either side of the mean plane formed by the other four atoms. The meth-oxy group is coplanar with the benzene ring to which it is connected [Cb-Cb-Om-Cm torsion angle = -0.2 (4)°; b = benzene and m = meth-oxy], and similarly the aldehyde is coplanar with respect to the double bond of the di-hydro-pyran ring [Cdh-Cdh-Ca-Oa = -178.1 (3)°; dh = di-hydro-pyran and a = aldehyde]. In the crystal, mol-ecules are linked by weak meth-yl-meth-oxy C-H⋯O hydrogen bonds into supra-molecular chains along the a-axis direction.

Synthesis and molecular structure of [Cu(NH3)4][Ni(CN)4]: A missing piece in the [Cu(NH3)n][Ni(CN)4] story

NASA Astrophysics Data System (ADS)

Solanki, Dina; Hogarth, Graeme

2015-11-01

Reaction of CuCl2·2H2O and K2[Ni(CN)4]·2H2O in aqueous ammonia gave blue rod-like crystals of [Cu(NH3)4][Ni(CN)4]. An X-ray crystallographic reveals that square-planar anions and cations are weakly associated through coordination of a cis pair of cyanide ligands to copper, with one short and one long contact and thus the copper centre is best described as a square-based pyramid. Crystals lose ammonia readily upon removal from the solvent and this has been probed by TGA and DSC measurements. For comparison we have also re-determined the structure of the related ethylenediamine (en) complex [Cu(en)2][Ni(CN)4] at 150 K. This consists of a 1D chain in which a trans pair of cyanide ligands bind to copper such that the latter has an overall tetragonally distorted octahedral coordination geometry.

Manipulating transmission and reflection properties of a photonic crystal doped with quantum dot nanostructures

DOE Office of Scientific and Technical Information (OSTI.GOV)

Solookinejad, G.; Panahi, M.; Sangachin, E. A.

The transmission and reflection properties of incident light in a defect dielectric structure is studied theoretically. The defect structure consists of donor and acceptor quantum dot nanostructures embedded in a photonic crystal. It is shown that the transmission and reflection properties of incident light can be controlled by adjusting the corresponding parameters of the system. The role of dipole–dipole interaction is considered as a new parameter in our calculations. It is noted that the features of transmission and reflection curves can be adjusted in the presence of dipole–dipole interaction. It is found that the absorption of weak probe light canmore » be converted to the probe amplification in the presence of dipole–dipole interaction. Moreover, the group velocity of transmitted and reflected probe light is discussed in detail in the absence and presence of dipole–dipole interaction. Our proposed model can be used as a new all-optical devices based on photonic materials doped with nanoparticles.« less

Crystalline Structure and Physical Properties of UCo2Al3

NASA Astrophysics Data System (ADS)

Verdín, E.; Escudero, R.

Some intermetallic compounds which contain uranium or cerium present heavy fermion characteristics. Take, for example, in the UM2Al3 (M=Pd, Ni) family, superconductivity and magnetism coexist and present heavy fermion behavior. This work presents the crystallographic characteristics and physical properties of a new compound of this family; the intermetallic compound UCo2Al3. Our initial crystallographic studies performed in a small single crystal show that the structure is hexagonal and similar to the UNi2Al3 and UPd2Al3 parent compounds. The space group is P6/mmm with a=5.125 Å and c=4.167 Å crystalline parameters. Measurements of resistivity and magnetization performed on the single crystal reveal that the compound is not superconducting when measured at about 1.8 K. The compound is highly anisotropic and features related to Kondo-like behavior are observed. A weak ferromagnetic transition is observed at a temperature of about 20 K.

Crystal structure of di-μ-chlorido-bis-(chlorido-{N1,N1-diethyl-N4-[(pyridin-2-yl-κN)methyl-idene]benzene-1,4-di-amine-κN4}mercury(II)).

PubMed

Faizi, Md Serajul Haque; Dege, Necmi; Goleva, Kateryna

2017-06-01

The title dinuclear mercury(II) complex, [Hg 2 Cl 4 (C 16 H 19 N 3 ) 2 ], synthesized from the pyridine-derived Schiff base ( E )- N 1 , N 1 -diethyl- N 4 -[(pyridin-2-yl)methyl-idene]benzene-1,4-di-amine (DPMBD), has inversion symmetry. The five-coordinated Hg II atoms have distorted square-pyramidal stereochemistry comprising two N-atom donors from bidentate chelate BPMBD ligands and three Cl-atom donors, two bridging and one monodentate. The dihedral angle between the benzene and the pyridine rings in the BPMBD ligand is 7.55 (4)°. In the crystal, the dinuclear mol-ecules are linked by weak C-H⋯Cl hydrogen bonds, forming zigzag ribbons lying parallel to [001]. Also present in the structure are π-π inter-actions between benzene and pyridine rings [minimum ring-centroid separation = 3.698 (8) Å].

Crystal Structure and Antiferromagnetic Ordering of Quasi-2D [Cu(HF2)(pyz)2]TaF6 (pyz=pyrazine)

NASA Astrophysics Data System (ADS)

Manson, J. L.; Schlueter, J. A.; McDonald, R. D.; Singleton, J.

2010-04-01

The crystal structure of the title compound was determined by X-ray diffraction at 90 and 295 K. Copper(II) ions are coordinated to four bridging pyz ligands to form square layers in the ab-plane. Bridging HF2- ligands join the layers together along the c-axis to afford a tetragonal, three-dimensional (3D) framework that contains TaF6- anions in every cavity. At 295 K, the pyz rings lie exactly perpendicular to the layers and cooling to 90 K induces a canting of those rings. Magnetically, the compound exhibits 2D antiferromagnetic correlations within the 2D layers with an exchange interaction of -13.1(1) K. Weak interlayer interactions, as mediated by Cu-F-H-F-Cu, leads to long-range magnetic order below 4.2 K. Pulsed-field magnetization data at 0.5 K show a concave curvature with increasing B and reveal a saturation magnetization at 35.4 T.

Crystal structure of an Fe-S cluster-containing fumarate hydratase enzyme from Leishmania major reveals a unique protein fold.

PubMed

Feliciano, Patricia R; Drennan, Catherine L; Nonato, M Cristina

2016-08-30

Fumarate hydratases (FHs) are essential metabolic enzymes grouped into two classes. Here, we present the crystal structure of a class I FH, the cytosolic FH from Leishmania major, which reveals a previously undiscovered protein fold that coordinates a catalytically essential [4Fe-4S] cluster. Our 2.05 Å resolution data further reveal a dimeric architecture for this FH that resembles a heart, with each lobe comprised of two domains that are arranged around the active site. Besides the active site, where the substrate S-malate is bound bidentate to the unique iron of the [4Fe-4S] cluster, other binding pockets are found near the dimeric enzyme interface, some of which are occupied by malonate, shown here to be a weak inhibitor of this enzyme. Taken together, these data provide a framework both for investigations of the class I FH catalytic mechanism and for drug design aimed at fighting neglected tropical diseases.

Shock compression modeling of metallic single crystals: comparison of finite difference, steady wave, and analytical solutions

DOE PAGES

Lloyd, Jeffrey T.; Clayton, John D.; Austin, Ryan A.; ...

2015-07-10

Background: The shock response of metallic single crystals can be captured using a micro-mechanical description of the thermoelastic-viscoplastic material response; however, using a such a description within the context of traditional numerical methods may introduce a physical artifacts. Advantages and disadvantages of complex material descriptions, in particular the viscoplastic response, must be framed within approximations introduced by numerical methods. Methods: Three methods of modeling the shock response of metallic single crystals are summarized: finite difference simulations, steady wave simulations, and algebraic solutions of the Rankine-Hugoniot jump conditions. For the former two numerical techniques, a dislocation density based framework describes themore » rate- and temperature-dependent shear strength on each slip system. For the latter analytical technique, a simple (two-parameter) rate- and temperature-independent linear hardening description is necessarily invoked to enable simultaneous solution of the governing equations. For all models, the same nonlinear thermoelastic energy potential incorporating elastic constants of up to order 3 is applied. Results: Solutions are compared for plate impact of highly symmetric orientations (all three methods) and low symmetry orientations (numerical methods only) of aluminum single crystals shocked to 5 GPa (weak shock regime) and 25 GPa (overdriven regime). Conclusions: For weak shocks, results of the two numerical methods are very similar, regardless of crystallographic orientation. For strong shocks, artificial viscosity affects the finite difference solution, and effects of transverse waves for the lower symmetry orientations not captured by the steady wave method become important. The analytical solution, which can only be applied to highly symmetric orientations, provides reasonable accuracy with regards to prediction of most variables in the final shocked state but, by construction, does not provide insight into the shock structure afforded by the numerical methods.« less

Monoalkylated barbiturate derivatives: X-ray crystal structure, theoretical studies, and biological activities

NASA Astrophysics Data System (ADS)

Barakat, Assem; Al-Majid, Abdullah Mohammed; Soliman, Saied M.; Islam, Mohammad Shahidul; Ghawas, Hussain Mansur; Yousuf, Sammer; Choudhary, M. Iqbal; Wadood, Abdul

2017-08-01

Barbiturate derivatives are privileged structures with a broad range of pharmaceutical applications. We prepared a series of 5-monoalkylated barbiturate derivatives (3a-l) and evaluated, in vitro, their antioxidant (DPPH assay), and α-glucosidase inhibitory activities. Compounds 3a-l were synthesized via Michael addition. The structure of compound 3k was determined using X-ray single-crystal diffraction, and geometric parameters were calculated using density functional theory at the B3LYP/6-311G(d,p) level of theory. Further, the structural analysis of 3k were also investigated. Biological studies revealed that compounds 3b (IC50 = 133.1 ± 3.2 μM), 3d (IC50 = 305 ± 7.7 μM), and 3e (IC50 = 184 ± 2.3 μM) have potent α-glucosidase enzyme inhibitors and showed greater activity than the standard drug acarbose (IC50 = 841 ± 1.73 μM). Compounds 3a-3i were found to show weak antioxidant activity against 1,1-diphenyl-2-picryl-hydrazyl (DPPH) radicals (IC50 = 91 ± 0.75 to 122 ± 1.0 μM) when tested against a standard antioxidant, gallic acid (IC50 = 23 ± 0.43 μM).

Electron paramagnetic resonance studies of slowly tumbling vanadyl spin probes in nematic liquid crystals

NASA Technical Reports Server (NTRS)

Bruno, G. V.; Harrington, J. K.; Eastman, M. P.

1978-01-01

An analysis of EPR line shapes by the method of Polnaszek, Bruno, and Freed is made for slowly tumbling vanadyl spin probes in viscous nematic liquid crystals. The use of typical vanadyl complexes as spin probes for nematic liquid crystals is shown to simplify the theoretical analysis and the subsequent interpretation. Rotational correlation times tau and orientational ordering parameters S sub Z where slow tumbling effects are expected to be observed in vanadyl EPR spectra are indicated in a plot. Analysis of the inertial effects on the probe reorientation, which are induced by slowly fluctuating torque components of the local solvent structure, yield quantitative values for tau and S sub Z. The weakly ordered probe VOAA is in the slow tumbling region and displays these inertial effects throughout the nematic range of BEPC and Phase V. VOAA exhibits different reorientation behavior near the isotropic-nematic transition temperature than that displayed far below this transition temperature.

Negative refraction imaging of acoustic metamaterial lens in the supersonic range

DOE Office of Scientific and Technical Information (OSTI.GOV)

Han, Jianning; Wen, Tingdun; Key Laboratory of Electronic Testing Technology, North University of China, Taiyuan 030051

2014-05-15

Acoustic metamaterials with negative refraction index is the most promising method to overcome the diffraction limit of acoustic imaging to achieve ultrahigh resolution. In this paper, we use localized resonant phononic crystal as the unit cell to construct the acoustic negative refraction lens. Based on the vibration model of the phononic crystal, negative quality parameters of the lens are obtained while excited near the system resonance frequency. Simulation results show that negative refraction of the acoustic lens can be achieved when a sound wave transmiting through the phononic crystal plate. The patterns of the imaging field agree well with thatmore » of the incident wave, while the dispersion is very weak. The unit cell size in the simulation is 0.0005 m and the wavelength of the sound source is 0.02 m, from which we show that acoustic signal can be manipulated through structures with dimensions much smaller than the wavelength of incident wave.« less

The role of boric acid in the synthesis of Eni Carbon Silicates.

PubMed

Zanardi, Stefano; Bellussi, Giuseppe; Parker, Wallace O'Neil; Montanari, Erica; Bellettato, Michela; Cruciani, Giuseppe; Carati, Angela; Guidetti, Stefania; Rizzo, Caterina; Millini, Roberto

2014-07-21

The influence of H3BO3 on the crystallization of hybrid organic-inorganic aluminosilicates denoted as Eni Carbon Silicates (ECS's) was investigated. Syntheses were carried out at 100 °C under different experimental conditions, using bridged silsesquioxanes of general formula (EtO)3Si-R-Si(OEt)3 (R = -C6H4- (BTEB), -C10H6- (BTEN) and -C6H4-C6H4- (BTEBP)), in the presence of equimolar concentrations of NaAlO2 and H3BO3. The study, involving the synthesis of three different but structurally related phases (ECS-14 from BTEB, ECS-13 here described for the first time from BTEN, and ECS-5 from BTEBP), confirmed a catalytic role for H3BO3 which in general increased the crystallization rate and improved the product quality in terms of amount of crystallized phase (crystallinity), size of the crystallites and phase purity, while it was weakly incorporated in trace amounts in the framework of ECS's.

Gapless quantum excitations from an icelike splayed ferromagnetic ground state in stoichiometric Yb 2 Ti 2 O 7

DOE PAGES

Gaudet, J.; Ross, K. A.; Kermarrec, E.; ...

2016-02-03

We know the ground state of the quantum spin ice candidate magnet Yb 2Ti 2O 7 to be sensitive to weak disorder at the similar to 1% level which occurs in single crystals grown from the melt. Powders produced by solid state synthesis tend to be stoichiometric and display large and sharp heat capacity anomalies at relatively high temperatures, T-C similar to 0.26 K. We have carried out neutron elastic and inelastic measurements on well characterized and equilibrated stoichiometric powder samples of Yb 2Ti 2O 7 which show resolution-limited Bragg peaks to appear at low temperatures, but whose onset correlatesmore » with temperatures much higher than T-C. The corresponding magnetic structure is best described as an icelike splayed ferromagnet. In the spin dynamics of Yb 2Ti 2O 7 we see the gapless on an energy scale <0.09 meV at all temperatures and organized into a continuum of scattering with vestiges of highly overdamped ferromagnetic spin waves present. These excitations differ greatly from conventional spin waves predicted for Yb 2Ti 2O 7's mean field ordered state, but appear robust to weak disorder as they are largely consistent with those displayed by nonstoichiometric crushed single crystals and single crystals, as well as by powder samples of Yb 2Ti 2O 7's sister quantum magnet Yb 2Ti 2O 7.« less

A Novel Energetic Perchlorate Amine Salt: Synthesis, Properties, and Density Functional Theory Calculation

NASA Astrophysics Data System (ADS)

Ma, Peng; Pan, Yong; Jiang, Juncheng; Zhu, Shunguan

2017-10-01

A novel explosive, ethylenediamine triethylenediamine tetraperchlorate (ETT), was synthesized by a rapid " one-pot" method. The molecular and crystal structures of ETT were determined by X-ray diffraction (XRD) and Fourier transformed infrared (FTIR) spectroscopy. The purity of the ETT was characterized by hydrogen nuclear magnetic resonance (H-NMR) spectra and elemental analysis (EA). The chemical and physical properties of the co-crystal ETT were further explored including impact sensitivity, velocity of detonation, and thermal behavior. The impact sensitivity of the ETT (h50% = 9.50 cm) is much lower than that of its components, ethylenediamine diperchlorate (ED) (h50% = 5.60 cm) and triethylenediamine diperchlorate (TD) (h50% = 2.10 cm). The measured detonation velocity is 8956 m/s (ρ = 1.873 g/cm3), which is much higher than that of TNT (6900 m/s) or RDX (8350 m/s). The co-crystal ETT shows a unique thermal behavior with a decomposition peak temperature at 365 °C. Band structure and density of states (DOS) of the ETT were confirmed by the CASTEP code. The first-principles tight-binding method within the general gradient approximation (GGA) was employed to study the electronic band structure as well as the DOS and Fermi energy. Hirshfeld surfaces were applied to analyze the intermolecular interactions in the co-crystal, and the results showed that weak interaction was dominantly mediated by H … O hydrogen bond. By analyzing the bond length at different temperatures, N-H covalent bond is the trigger bond for the ETT.

On the roles of close shell interactions in the structure of acyl-substituted hydrazones: An experimental and theoretical approach

NASA Astrophysics Data System (ADS)

Saeed, Aamer; Ifzan Arshad, M.; Bolte, Michael; Fantoni, Adolfo C.; Delgado Espinoza, Zuly Y.; Erben, Mauricio F.

2016-03-01

The 2-(phenyl-hydrazono)-succinic acid dimethyl ester compound was synthesized by reacting phenylhydrazine with dimethylacetylene dicarboxylate at room temperature and characterized by elemental analysis, infrared, Raman, 1H and 13C NMR spectroscopies and mass spectrometry. Its solid state structure was determined by X-ray diffraction methods. The X-ray structure determination corroborates that the molecule is present in the crystal as the hydrazone tautomer, probably favored by a strong intramolecular N-H···Odbnd C hydrogen bond occurring between the carbonyl (-Cdbnd O) and the hydrazone -Cdbnd N-NH- groups. A substantial fragment of the molecular skeleton is planar due to an extended π-bonding delocalization. The topological analysis of the electron densities (Atom in Molecule, AIM) allows characterization of intramolecular N-H···O interaction, that can be classified as a resonant assisted hydrogen bond (RAHB). Moreover, the Natural Bond Orbital population analysis confirms that a strong hyperconjugative lpO1 → σ*(N2-H) remote interaction between the C2dbnd O1 and N2-H groups takes place. Periodic system electron density and topological analysis have been applied to characterize the intermolecular interactions in the crystal. Weak intermolecular interactions determine the crystal packing, and the prevalence of non-directional dispersive contributions are inferred on topological grounds. The IR spectrum of the crystalline compound was investigated by means of density functional theory calculations carried out with periodic boundary conditions on the crystal, showing excellent agreement between theory and the experiments. The vibrational assignment is complemented with the analysis of the Raman spectrum.

New metal-organic frameworks of [M(C6H5O7)(C6H6O7)(C6H7O7)(H2O)] . H2O (M=La, Ce) and [Ce2(C2O4)(C6H6O7)2] . 4H2O

NASA Astrophysics Data System (ADS)

Weng, Sheng-Feng; Wang, Yun-Hsin; Lee, Chi-Shen

2012-04-01

Two novel materials, [M(C6H5O7)(C6H6O7)(C6H7O7)(H2O)] . H2O (M=La(1a), Ce(1b)) and [Ce2(C2O4)(C6H6O7)2] . 4H2O (2), with a metal-organic framework (MOF) were prepared with hydrothermal reactions and characterized with photoluminescence, magnetic susceptibility, thermogravimetric analysis and X-ray powder diffraction in situ. The crystal structures were determined by single-crystal X-ray diffraction. Compound 1 crystallized in triclinic space group P1¯ (No. 2); compound 2 crystallized in monoclinic space group P21/c (No. 14). The structure of 1 is built from a 1D MOF, composed of deprotonated citric ligands of three kinds. Compound 2 contains a 2D MOF structure consisting of citrate and oxalate ligands; the oxalate ligand arose from the decomposition in situ of citric acid in the presence of CuII ions. Photoluminescence spectra of compounds 1b and 2 revealed transitions between the 5d1 excited state and two levels of the 4f1 ground state (2F5/2 and 2F7/2). Compounds 1b and 2 containing CeIII ion exhibit a paramagnetic property with weak antiferromagnetic interactions between the two adjacent magnetic centers.

Research Associate | Center for Cancer Research

Cancer.gov

PROGRAM DESCRIPTION The Basic Science Program (BSP) pursues independent, multidisciplinary research in basic and applied molecular biology, immunology, retrovirology, cancer biology, and human genetics. Research efforts and support are an integral part of the Center for Cancer Research (CCR) at the Frederick National Laboratory for Cancer Research (FNLCR). KEY ROLES/RESPONSIBILITIES - Research Associate III Dr. Zbigniew Dauter is the head investigator of the Synchrotron Radiation Research Section (SRRS) of CCR’s Macromolecular Crystallography Laboratory. The Synchrotron Radiation Research Section is located at Argonne National Laboratory, Argonne, Illinois; this is the site of the largest U.S. synchrotron facility. The SRRS uses X-ray diffraction technique to solve crystal structures of various proteins and nucleic acids of biological and medical relevance. The section is also specializing in analyzing crystal structures at extremely high resolution and accuracy and in developing methods of effective diffraction data collection and in using weak anomalous dispersion effects to solve structures of macromolecules. The areas of expertise are: Structural and molecular biology Macromolecular crystallography Diffraction data collection Dr. Dauter requires research support in these areas, and the individual will engage in the purification and preparation of samples, crystallize proteins using various techniques, and derivatize them with heavy atoms/anomalous scatterers, and establish conditions for cryogenic freezing. Individual will also participate in diffraction data collection at the Advanced Photon Source. In addition, the candidate will perform spectroscopic and chromatographic analyses of protein and nucleic acid samples in the context of their purity, oligomeric state and photophysical properties.

Crystal structure of the inactive state of the receiver domain of Spo0A from Paenisporosarcina sp. TG-14, a psychrophilic bacterium isolated from an Antarctic glacier.

PubMed

Lee, Chang Woo; Park, Sun-Ha; Lee, Sung Gu; Shin, Seung Chul; Han, Se Jong; Kim, Han-Woo; Park, Hyun Ho; Kim, Sunghwan; Kim, Hak Jun; Park, Hyun; Park, HaJeung; Lee, Jun Hyuck

2017-06-01

The two-component phosphorelay system is the most prevalent mechanism for sensing and transducing environmental signals in bacteria. Spore formation, which relies on the two-component phosphorelay system, enables the long-term survival of the glacial bacterium Paenisporosarcina sp. TG-14 in the extreme cold environment. Spo0A is a key response regulator of the phosphorelay system in the early stage of spore formation. The protein is composed of a regulatory N-terminal phospho-receiver domain and a DNA-binding C-terminal activator domain. We solved the three-dimensional structure of the unphosphorylated (inactive) form of the receiver domain of Spo0A (PaSpo0A-R) from Paenisporosarcina sp. TG-14. A structural comparison with phosphorylated (active form) Spo0A from Bacillus stearothermophilus (BsSpo0A) showed minor notable differences. A molecular dynamics study of a model of the active form and the crystal structures revealed significant differences in the α4 helix and the preceding loop region where phosphorylation occurs. Although an oligomerization study of PaSpo0A-R by analytical ultracentrifugation (AUC) has shown that the protein is in a monomeric state in solution, both crosslinking and crystal-packing analyses indicate the possibility of weak dimer formation by a previously undocumented mechanism. Collectively, these observations provide insight into the mechanism of phosphorylation-dependent activation unique to Spo0A.

Crystal structure of octa-kis-(4-meth-oxy-pyridinium) bis-(4-meth-oxy-pyridine-κN)tetra-kis-(thio-cyanato-κN)ferrate(III) bis-[(4-meth-oxypyri-dine-κN)pentakis-(thio-cyanato-κN)ferrate(III)] hexa-kis-(thio-cyanato-κN)ferrate(III) with iron in three different octa-hedral coordination environments.

PubMed

Jochim, Aleksej; Jess, Inke; Näther, Christian

2018-03-01

The crystal structure of the title salt, (C 6 H 8 NO) 8 [Fe(NCS) 4 (C 6 H 7 NO) 2 ][Fe(NCS) 5 (C 6 H 7 NO)] 2 [Fe(NCS) 6 ], comprises three negatively charged octa-hedral Fe III complexes with different coordination environments in which the Fe III atoms are coordinated by a different number of thio-cyanate anions and 4-meth-oxy-pyridine ligands. Charge balance is achieved by 4-meth-oxy-pyridinium cations. The asymmetric unit consists of three Fe III cations, one of which is located on a centre of inversion, one on a twofold rotation axis and one in a general position, and ten thio-cyanate anions, two 4-meth-oxy-pyridine ligands and 4-meth-oxy-pyridinium cations (one of which is disordered over two sets of sites). Beside to Coulombic inter-actions between organic cations and the ferrate(III) anions, weak N-H⋯S hydrogen-bonding inter-actions involving the pyridinium N-H groups of the cations and the thio-cyanate S atoms of the complex anions are mainly responsible for the cohesion of the crystal structure.

Synthesis and crystal structure of Fe[(Te1.5Se0.5)O5]Cl, the first iron compound with selenate(IV) and tellurate(IV) groups

NASA Astrophysics Data System (ADS)

Akhrorov, Akhmad Yu; Kuznetsova, Elena S.; Aksenov, Sergey M.; Berdonosov, Peter S.; Kuznetsov, Alexey N.; Dolgikh, Valery A.

2017-12-01

During the search for selenium analogues of FeTe2O5Cl, the new iron (III) tellurate(IV) selenate(IV) chloride with the composition Fe[(Te1.5Se0.5)O5]Cl was synthesized by chemical vapor transport (CVT) reaction and characterized by TGA-, EDX-,SCXRD-analysis, as well as IR and Raman spectroscopy. It was found that Fe[(Te1.5Se0.5)O5]Cl crystallizes in the monoclinic space group P21/c with unitcell parameters a = 5.183(3) Å, b = 15.521(9) Å, c = 7.128(5) Å and β = 107.16(1)°. The crystal structure of Fe[(Te1.5Se0.5)O5]Cl represents a new structure type and contains electroneutral heteropolyhedral layers formed by dimers of the [FeO5Cl]8- octahedra, linked via common O-O edges, and mixed [Te3SeO10]4- tetramers. Adjacent layers are stacked along the b axis and linked by weak residual bonds. The new compound is stable up to 420 °C. DFT calculations predict Fe[(Te1.5Se0.5)O5]Cl to be a wide-gap semiconductor with the band gap of ca. 2.7 eV.

Cooperativity of anion⋯π and π⋯π interactions regulates the self-assembly of a series of carbene proligands: Towards quantitative analysis of intermolecular interactions with Hirshfeld surface

NASA Astrophysics Data System (ADS)

Samanta, Tapastaru; Dey, Lingaraj; Dinda, Joydev; Chattopadhyay, Shyamal Kumar; Seth, Saikat Kumar

2014-06-01

The cooperative effect of weak non-covalent forces between anions and electron deficient aromatics by π⋯π stacking of a series of carbene proligands (1-3) have been thoroughly explored by crystallographic studies. Structural analysis revealed that the anion⋯π and π⋯π interactions along with intermolecular hydrogen bonding mutually cooperate to facilitate the assembling of the supramolecular framework. The π⋯π and corresponding anion⋯π interactions have been investigated in the title carbene proligands despite their association with counter ions. The presence of the anion in the vicinity of the π-system leads to the formation of anion⋯π/π⋯π/π⋯anion network for an inductive stabilization of the assemblies. To assess the dimensionality of the supramolecular framework consolidated by cooperative anion⋯π/π⋯π interactions and hydrogen bonding, different substituent effects in the carbene backbone have been considered to tune these interactions. These facts show that the supramolecular framework based on these cooperative weak forces may be robust enough for application in molecular recognition. The investigation of close intermolecular interactions between the molecules via Hirshfeld surface analyses is presented in order to reveal subtle differences and similarities in the crystal structures. The decomposition of the fingerprint plot area provides a percentage of each intermolecular interaction, allowing for a quantified analysis of close contacts within each crystal.

First-principles studies of phase stability and crystal structures in Li-Zn mixed-metal borohydrides

NASA Astrophysics Data System (ADS)

Wang, Yongli; Zhang, Yongsheng; Wolverton, C.

2013-07-01

We address the problem of finding mixed-metal borohydrides with favorable thermodynamics and illustrate the approach using the example of LiZn2(BH4)5. Using density functional theory (DFT), along with the grand-canonical linear programming method (GCLP), we examine the experimentally and computationally proposed crystal structures and the finite-temperature thermodynamics of dehydrogenation for the quaternary hydride LiZn2(BH4)5. We find the following: (i) For LiZn2(BH4)5, DFT calculations of the experimental crystal structures reveal that the structure from the neutron diffraction experiments of Ravnsbæk is more stable [by 24 kJ/(mol f.u.)] than that based on a previous x-ray study. (ii) Our DFT calculations show that when using the neutron-diffraction structure of LiZn2(BH4)5, the recently theoretically predicted LiZn(BH4)3 compound is unstable with respect to the decomposition into LiZn2(BH4)5+LiBH4. (iii) GCLP calculations show that even though LiZn2(BH4)5 is a combination of weakly [Zn(BH4)2] and strongly (LiBH4) bound borohydrides, its decomposition is not intermediate between the two individual borohydrides. Rather, we find that the decomposition of LiZn2(BH4)5 is divided into a weakly exothermic step [LiZn2(BH4)5→2Zn+(1)/(5)LiBH4+(2)/(5)Li2B12H12+(36)/(5)H2] and three strong endothermic steps (12LiBH4→10LiH+Li2B12H12+13H2; Zn+LiH→LiZn+(1)/(2)H2; 2Zn+Li2B12H12→2LiZn+12B+6H2). DFT-calculated ΔHZPET=0K values for the first three LiZn2(BH4)5 decomposition steps are -19, +37, +74 kJ/(mol H2), respectively. The behavior of LiZn2(BH4)5 shows that mixed-metal borohydrides formed by mixing borohydrides of high and low thermodynamics stabilities do not necessarily have an intermediate decomposition tendency. Our results suggest the correct strategy to find intermediate decomposition in mixed-metal borohydrides is to search for stable mixed-metal products such as ternary metal borides.

Activator anion binding site in pyridoxal phosphorylase b: the binding of phosphite, phosphate, and fluorophosphate in the crystal.

PubMed Central

Oikonomakos, N. G.; Zographos, S. E.; Tsitsanou, K. E.; Johnson, L. N.; Acharya, K. R.

1996-01-01

It has been established that phosphate analogues can activate glycogen phosphorylase reconstituted with pyridoxal in place of the natural cofactor pyridoxal 5'-phosphate (Change YC. McCalmont T, Graves DJ. 1983. Biochemistry 22:4987-4993). Pyridoxal phosphorylase b has been studied by kinetic, ultracentrifugation, and X-ray crystallographic experiments. In solution, the catalytically active species of pyridoxal phosphorylase b adopts a conformation that is more R-state-like than that of native phosphorylase b, but an inactive dimeric species of the enzyme can be stabilized by activator phosphite in combination with the T-state inhibitor glucose. Co-crystals of pyridoxal phosphorylase b complexed with either phosphite, phosphate, or fluorophosphate, the inhibitor glucose, and the weak activator IMP were grown in space group P4(3)2(1)2, with native-like unit cell dimensions, and the structures of the complexes have been refined to give crystallographic R factors of 18.5-19.2%, for data between 8 and 2.4 A resolution. The anions bind tightly at the catalytic site in a similar but not identical position to that occupied by the cofactor 5'-phosphate group in the native enzyme (phosphorus to phosphorus atoms distance = 1.2 A). The structural results show that the structures of the pyridoxal phosphorylase b-anion-glucose-IMP complexes are overall similar to the glucose complex of native T-state phosphorylase b. Structural comparisons suggest that the bound anions, in the position observed in the crystal, might have a structural role for effective catalysis. PMID:8976550

Characterizing the Atomic Structure in Low Concentrations of Weakly Ordered, Weakly Scattering Materials Using the Pair Distribution Function

NASA Astrophysics Data System (ADS)

Terban, Maxwell W.

Nanoscale structural characterization is critical to understanding the physical underpinnings of properties and behavior in materials with technological applications. The work herein shows how the pair distribution function technique can be applied to x-ray total scattering data for material systems which weakly scatter x-rays, a typically difficult task due to the poor signal-to-noise obtained from the structures of interest. Characterization and structural modeling are demonstrated for a variety of molecular and porous systems, along with the detection and characterization of disordered, minority phases and components. In particular, reliable detection and quantitative analysis are demonstrated for nanocrystals of an active pharmaceutical ingredient suspended in dilute solution down to a concentration of 0.25 wt. %, giving a practical limit of detection for ordered nanoscale phases within a disordered matrix. Further work shows that minority nanocrystalline phases can be detected, fingerprinted, and modeled for mixed crystalline and amorphous systems of small molecules and polymers. The crystallization of amorphous lactose is followed under accelerated aging conditions. Melt quenching is shown to produce a different local structure than spray drying or freeze drying, along with increased resistance to crystallization. The initial phases which form in the spray dried formulation are identified as a mixture of polymorphs different from the final alpha-lactose monohydrate form. Hard domain formation in thermoplastic polyurethanes is also characterized as a function of methylene diphenyl diisocyanate and butanediol component ratio, showing that distinct and different hard phase structures can form and are solved by indexing with structures derived from molecular dynamics relaxation. In both cases, phase fractions can be quantified in the mixed crystalline and amorphous systems by fitting with both standards or structure models. Later chapters, demonstrate pair distribution characterization of particle incorporation, structure, and synthesis of nanoporous materials. Nanoparticle size distributions are extracted from platinum nanoparticles nucleating within a zeolite matrix through structural modeling, and validated by transmission electron microscope studies. The structure of zirconium phosphonate-phosphate unconventional metal organic framework is determined to consist of turbostratically disordered nanocrystalline layers of Zr-phenylphosphonate, and the local environment of terbium intercalated between the layers is found to resemble the local environment in scheelite-type terbium phosphate. Finally, the early stages of reaction between aqueous zinc dinitrate hexahydrate and methanolic 2-methylimidazole are characterized using in situ total scattering measurements, showing that secondary building units of tetrahedrally coordinated by 2-methylimidazole initially form upon reaction. Overall, the methodologies are developed and applied toward phase detection, identification, solution, and behavior in pharmaceuticals, polymers, and nanoporous materials along with advice for carrying out experiments and analysis on such materials such that they can be extended to other similar systems.

Structure of the cyanobactin oxidase ThcOx from Cyanothece sp. PCC 7425, the first structure to be solved at Diamond Light Source beamline I23 by means of S-SAD.

PubMed

Bent, Andrew F; Mann, Greg; Houssen, Wael E; Mykhaylyk, Vitaliy; Duman, Ramona; Thomas, Louise; Jaspars, Marcel; Wagner, Armin; Naismith, James H

2016-11-01

Determination of protein crystal structures requires that the phases are derived independently of the observed measurement of diffraction intensities. Many techniques have been developed to obtain phases, including heavy-atom substitution, molecular replacement and substitution during protein expression of the amino acid methionine with selenomethionine. Although the use of selenium-containing methionine has transformed the experimental determination of phases it is not always possible, either because the variant protein cannot be produced or does not crystallize. Phasing of structures by measuring the anomalous diffraction from S atoms could in theory be almost universal since almost all proteins contain methionine or cysteine. Indeed, many structures have been solved by the so-called native sulfur single-wavelength anomalous diffraction (S-SAD) phasing method. However, the anomalous effect is weak at the wavelengths where data are normally recorded (between 1 and 2 Å) and this limits the potential of this method to well diffracting crystals. Longer wavelengths increase the strength of the anomalous signal but at the cost of increasing air absorption and scatter, which degrade the precision of the anomalous measurement, consequently hindering phase determination. A new instrument, the long-wavelength beamline I23 at Diamond Light Source, was designed to work at significantly longer wavelengths compared with standard synchrotron beamlines in order to open up the native S-SAD method to projects of increasing complexity. Here, the first novel structure, that of the oxidase domain involved in the production of the natural product patellamide, solved on this beamline is reported using data collected to a resolution of 3.15 Å at a wavelength of 3.1 Å. The oxidase is an example of a protein that does not crystallize as the selenium variant and for which no suitable homology model for molecular replacement was available. Initial attempts collecting anomalous diffraction data for native sulfur phasing on a standard macromolecular crystallography beamline using a wavelength of 1.77 Å did not yield a structure. The new beamline thus has the potential to facilitate structure determination by native S-SAD phasing for what would previously have been regarded as very challenging cases with modestly diffracting crystals and low sulfur content.

General synthesis of inorganic single-walled nanotubes

PubMed Central

Ni, Bing; Liu, Huiling; Wang, Peng-peng; He, Jie; Wang, Xun

2015-01-01

The single-walled nanotube (SWNT) is an interesting nanostructure for fundamental research and potential applications. However, very few inorganic SWNTs are available to date due to the lack of efficient fabrication methods. Here we synthesize four types of SWNT: sulfide; hydroxide; phosphate; and polyoxometalate. Each type of SWNT possesses essentially uniform diameters. Detailed studies illustrate that the formation of SWNTs is initiated by the self-coiling of the corresponding ultrathin nanostructure embryo/building blocks on the base of weak interactions between them, which is not limited to specific compounds or crystal structures. The interactions between building blocks can be modulated by varying the solvents used, thus multi-walled tubes can also be obtained. Our results reveal that the generalized synthesis of inorganic SWNTs can be achieved by the self-coiling of ultrathin building blocks under the proper weak interactions. PMID:26510862

Signal Transduction in Histidine Kinases: Insights from New Structures

PubMed Central

Bhate, Manasi P.; Molnar, Kathleen S.; Goulian, Mark; DeGrado, William F.

2015-01-01

Histidine kinases (HKs) are major players in bacterial signaling. There has been an explosion of new HK crystal structures in the last five years. We globally analyze the structures of HKs to yield insights into the mechanisms by which signals are transmitted to and across protein structures in this family. We interpret known enzymological data in the context of new structural data to show how asymmetry across the dimer interface is a key feature of signal transduction in HKs, and discuss how different HK domains undergo asymmetric-to-symmetric transitions during signal transduction and catalysis. A thermodynamic framework for signaling that encompasses these various properties is presented and the consequences of weak thermodynamic coupling are discussed. The synthesis of observations from enzymology, structural biology, protein engineering and thermodynamics paves the way for a deeper molecular understanding of histidine kinase signal transduction. PMID:25982528

Commensurability and stability in nonperiodic systems

PubMed Central

Fasano, Y.; De Seta, M.; Menghini, M.; Pastoriza, H.; de la Cruz, F.

2005-01-01

We have investigated the response of 3D Bi2Sr2CaCu2O8 vortex structures to a weak perturbation induced by 2D Fe pinning structures acting on one extremity of vortex lines. The pinning patterns were nano-engineered at the sample surface by means of either a Bitter decoration of the vortex lattice or electron-beam lithography. The commensurability conditions between 2D rigid pinning potentials and 3D elastic structures with short-range positional and long-range orientational correlation have been experimentally determined. When the 2D potential is a replica of the nonperiodic vortex structure an amplification of its interaction with the vortex structure takes place. This effect is detected only for the first matching field, becoming negligible for other matching fields. On the other hand, a periodic 2D perturbation is shown to transform the nonperiodic Bragg glass-like structure into an Abrikosov crystal with an effective Debye–Waller factor. PMID:16576763

Inelastic neutron scattering, Raman, vibrational analysis with anharmonic corrections, and scaled quantum mechanical force field for polycrystalline L-alanine

NASA Astrophysics Data System (ADS)

Williams, Robert W.; Schlücker, Sebastian; Hudson, Bruce S.

2008-01-01

A scaled quantum mechanical harmonic force field (SQMFF) corrected for anharmonicity is obtained for the 23 K L-alanine crystal structure using van der Waals corrected periodic boundary condition density functional theory (DFT) calculations with the PBE functional. Scale factors are obtained with comparisons to inelastic neutron scattering (INS), Raman, and FT-IR spectra of polycrystalline L-alanine at 15-23 K. Calculated frequencies for all 153 normal modes differ from observed frequencies with a standard deviation of 6 wavenumbers. Non-bonded external k = 0 lattice modes are included, but assignments to these modes are presently ambiguous. The extension of SQMFF methodology to lattice modes is new, as are the procedures used here for providing corrections for anharmonicity and van der Waals interactions in DFT calculations on crystals. First principles Born-Oppenheimer molecular dynamics (BOMD) calculations are performed on the L-alanine crystal structure at a series of classical temperatures ranging from 23 K to 600 K. Corrections for zero-point energy (ZPE) are estimated by finding the classical temperature that reproduces the mean square displacements (MSDs) measured from the diffraction data at 23 K. External k = 0 lattice motions are weakly coupled to bonded internal modes.

Guignardones P-S, New Meroterpenoids from the Endophytic Fungus Guignardia mangiferae A348 Derived from the Medicinal Plant Smilax glabra.

PubMed

Sun, Zhang-Hua; Liang, Fa-Liang; Wu, Wen; Chen, Yu-Chan; Pan, Qing-Ling; Li, Hao-Hua; Ye, Wei; Liu, Hong-Xin; Li, Sai-Ni; Tan, Guo-Hui; Zhang, Wei-Min

2015-12-21

Four new meroterpenoids, guignardones P-S (1-4), and three known analogues (5-7) were isolated from the endophytic fungal strain Guignardia mangiferae A348. Their structures were elucidated on the basis of spectroscopic analysis and single crystal X-ray diffraction. All the isolated compounds were evaluated for their inhibitory effects on SF-268, MCF-7, and NCI-H460 human cancer cell lines. Compounds 2 and 4 exhibited weak inhibitions of cell proliferation against MCF-7 cell line.

1-(4,4''-Difluoro-5'-meth-oxy-1,1':3',1''-terphenyl-4'-yl)ethanone.

PubMed

Fun, Hoong-Kun; Hemamalini, Madhukar; Samshuddin, S; Narayana, B; Sarojini, B K

2012-01-01

In the title compound, C(21)H(16)F(2)O(2), the central benzene ring is inclined at dihedral angles of 30.91 (8) and 46.88 (7)° to the two terminal fluoro-substituted rings. The dihedral angle between the two terminal fluoro-subsituted rings is 68.34 (8)°. An intra-molecular C-H⋯O hydrogen bond generates an S(6) ring motif. The crystal structure is stabilized by weak C-H⋯π inter-actions.

Subsurface bending and reorientation of tilted vortex lattices in bulk isotropic superconductors due to Coulomb-like repulsion at the surface

DOE Office of Scientific and Technical Information (OSTI.GOV)

Herrera, E.; Guillamón, I.; Galvis, J. A.

Here, we study vortex lattices (VLs) in superconducting weak-pinning platelet-like single crystals of β–Bi 2Pd in tilted magnetic fields with a scanning tunneling microscope. We show that vortices exit the sample perpendicular to the surface and are thus bent beneath the surface. The structure and orientation of the tilted VLs in the bulk are, for large tilt angles, strongly affected by Coulomb-type intervortex repulsion at the surface due to stray magnetic fields.

Proton conduction in electrolyte made of manganese dioxide for hydrogen gas sensor

DOE Office of Scientific and Technical Information (OSTI.GOV)

Koyanaka, Hideki; Ueda, Yoshikatsu; Takeuchi, K

2012-01-01

We propose a network model of oxygen-pairs to store and conduct protons on the surface of manganese dioxide with a weak covalent bond like protons stored in pressured ice. The atomic distances of oxygen-pairs were estimated between 2.57 and 2.60 angstroms in crystal structures of ramsdellite-type and lambda-type manganese dioxides by using protonated samples and inelastic neutron scattering measurements. Good properties for a hydrogen gas sensor using electrolytes made of manganese dioxides that contain such oxygen-pairs were confirmed experimentally.

2,2′-(Carbono­thio­yldisulfanedi­yl)bis­(2-methyl­propanoic acid)

PubMed Central

Moreno-Fuquen, Rodolfo; Grande, Carlos; Advincula, Rigoberto C.; Tenorio, Juan C.; Ellena, Javier

2013-01-01

The mol­ecular structure of the title compound, C9H14O4S3, exhibits intra­molecular C—H⋯S hydrogen bonds. In the crystal, pairs of O—H⋯O hydrogen bonds lead to the formation of centrosymmetric dimers, which are in turn connected by weak C—H⋯O inter­actions. The combination of these inter­actions generates edge-fused R 2 2(8) and R 2 2(20) rings running along [211]. PMID:23723918

The influence of water on the physicochemical characteristics of 1-butyl-3-methylimidazolium bromide ionic liquid

NASA Astrophysics Data System (ADS)

Ramenskaya, L. M.; Grishina, E. P.; Pimenova, A. M.; Gruzdev, M. S.

2008-07-01

A modified synthesis of 1-butyl-3-methylimidazolium bromide (BMImBr) was suggested and performed, and some physicochemical properties of the product containing 0.64 13.6 wt % water were determined. Water increased the electrical conductivity and decreased the viscosity and melting point of the substance but weakly influenced its density. Water in amounts of 5 8 wt % (45 50 mol %) caused structural changes. The BMImBr · 0.5H2O crystal hydrate was found to be stable thermodynamically.

Subsurface bending and reorientation of tilted vortex lattices in bulk isotropic superconductors due to Coulomb-like repulsion at the surface

DOE PAGES

Herrera, E.; Guillamón, I.; Galvis, J. A.; ...

2017-11-03

Here, we study vortex lattices (VLs) in superconducting weak-pinning platelet-like single crystals of β–Bi 2Pd in tilted magnetic fields with a scanning tunneling microscope. We show that vortices exit the sample perpendicular to the surface and are thus bent beneath the surface. The structure and orientation of the tilted VLs in the bulk are, for large tilt angles, strongly affected by Coulomb-type intervortex repulsion at the surface due to stray magnetic fields.

Selective cytotoxic eremophilane-type sesquiterpenes from Penicillium citreonigrum.

PubMed

Yuan, Wei-Hua; Goto, Masuo; Hsieh, Kan-Yen; Yuan, Bo; Zhao, Yu; Morris-Natschke, Susan L; Lee, Kuo-Hsiung

2015-01-01

One new eremophilane-type sesquiterpene (1, citreopenin) was isolated from Penicillium citreonigrum (HQ738282), and the structure was elucidated by a combination of spectroscopic data interpretation and single-crystal X-ray diffraction analysis using Cu Kα radiation (CCDC 1030588). Compound 1 showed weak activity against KB-VIN (IC50 = 11.0 ± 0.156 μM), while the known compound 3 exhibited selective cytotoxicity against MDA-MB-231 triple-negative breast cancer (TNBC) (IC50 = 5.42 ± 0.167 μM).

Temperature-controlled two new Co(II) compounds with distinct topological networks: Syntheses, crystal structures and catalytic properties

NASA Astrophysics Data System (ADS)

Meng, Qing-Hua; Long, Xu; Liu, Jing-Li; Zhang, Shuan; Zhang, Guang-Hui

2018-04-01

Two new Co(II) coordination compounds, namely [Co2(bptc)(bpp)2]n (1) and [Co(bptc)0.5(bpp)]n (2) (H4bptc = biphenyl-3,3‧,5,5‧-tetracarboxylic acid, bpp = 1,3-di(4-pyridyl)propane), have been hydrothermally synthesized from the same reactants via tuning the reaction temperature. Single crystal X-ray diffraction analyses revealed that both 1 and 2 feature 2D sheet motifs. Topological analyses revealed that compounds 1 and 2 show distinct topological networks. Under the weak Van der Waals interactions, the 2D sheet motifs of compounds 1 and 2 are further packed into 2D→3D interdigitated supramolecular frameworks. Moreover, the two Co(II) compounds show high catalytic activities for degradation of methyl orange (MO) in a Fenten-like process.

Crystal structure of 9-butyl-6-[2-(pyridin-4-yl)ethen­yl]carbazol-3-amine

PubMed Central

Zhang, Ping; Bai, Xiang-Yang; Zhang, Ting

2015-01-01

The asymmetric unit of the title compound, C23H23N3, consists of two mol­ecules, A and B, with different conformations. In mol­ecule A, the dihedral angle between the carbazole ring system (r.m.s. deviation = 0.028 Å) and the pyridine ring is 20.28 (9)° and the N—C—C—C torsion angle of the butyl side chain is −63.4 (3)°. The equivalent data for mol­ecule B are 0.065 Å, 48.28 (11)° and 61.0 (3)°, respectively. In the crystal, the components are connected by weak N—H⋯N hydrogen bonds, generating [030] C(14) chains of alternating A and B mol­ecules. PMID:25995940

Crystal structure of quinolinium 2-carboxy-6-nitro-benzoate monohydrate.

PubMed

Mohana, J; Divya Bharathi, M; Ahila, G; Chakkaravarthi, G; Anbalagan, G

2015-05-01

In the anion of the title hydrated mol-ecular salt, C9H8N(+)·C8H4NO6 (-)·H2O, the protonated carboxyl and nitro groups makes dihedral angles of 27.56 (5) and 6.86 (8)°, respectively, with the attached benzene ring, whereas the deprotonated carb-oxy group is almost orthogonal to it with a dihedral angle of 80.21 (1)°. In the crystal, the components are linked by O-H⋯O and N-H⋯O hydrogen bonds, generating [001] chains. The packing is consolidated by weak C-H⋯N and C-H⋯O inter-actions as well as aromatic π-π stacking [centroid-to-centroid distances: 3.7023 (8) & 3.6590 (9)Å] inter-actions, resulting in a three-dimensional network.

Role of S…O non-bonded interaction in controlling supramolecular assemblies in a new series of 2-aminobenzothiazole based organic salts/ co-crystals

NASA Astrophysics Data System (ADS)

Yadav, Priyanka; Patel, Vatsa; Ballabh, Amar

2018-07-01

A new series of 2-aminobenzothiazole based organic salts were synthesized with mono- / di-carboxylic acid and characterized with various physico-chemical methods. One of the synthesized salt 2-aminobenzothiazolium-hydrogen fumarate (BTzA4) was found to be capable of gelling water with minimum gelator concentration (MGC) around 1.25 wt% (w/v). The single crystal structures of gelator (BTzA4) and non-gelators were analyzed for the presence of various supramolecular synthons especially the rarely occurring non-bonded S…O interactions and their role in controlling the overall hydrogen bonded network in these series of salts/ cocrystals. Charge assisted hydrogen bonded network was found to be governing the weak non-bonded S…O supramolecular synthons in the present study.

Crystal structure of N-{[3-bromo-1-(phenyl-sulfon-yl)-1H-indol-2-yl]meth-yl}benzene-sulfonamide.

PubMed

Umadevi, M; Raju, P; Yamuna, R; Mohanakrishnan, A K; Chakkaravarthi, G

2015-10-01

In the title compound, C21H17BrN2O4S2, the indole ring system subtends dihedral angles of 85.96 (13) and 9.62 (16)° with the planes of the N- and C-bonded benzene rings, respectively. The dihedral angles between the benzene rings is 88.05 (17)°. The mol-ecular conformation is stabilized by intra-molecular N-H⋯O and C-H⋯O hydrogen bonds and an aromatic π-π stacking [centroid-to-centroid distance = 3.503 (2) Å] inter-action. In the crystal, short Br⋯O [2.9888 (18) Å] contacts link the mol-ecules into [010] chains. The chains are cross-linked by weak C-H⋯π inter-actions, forming a three-dimensional network.

Photonic crystal resonances for sensing and imaging

NASA Astrophysics Data System (ADS)

Pitruzzello, Giampaolo; Krauss, Thomas F.

2018-07-01

This review provides an insight into the recent developments of photonic crystal (PhC)-based devices for sensing and imaging, with a particular emphasis on biosensors. We focus on two main classes of devices, namely sensors based on PhC cavities and those on guided mode resonances (GMRs). This distinction is able to capture the richness of possibilities that PhCs are able to offer in this space. We present recent examples highlighting applications where PhCs can offer new capabilities, open up new applications or enable improved performance, with a clear emphasis on the different types of structures and photonic functions. We provide a critical comparison between cavity-based devices and GMR devices by highlighting strengths and weaknesses. We also compare PhC technologies and their sensing mechanism to surface plasmon resonance, microring resonators and integrated interferometric sensors.

A study of the solvent effect on the morphology of RDX crystal by molecular modeling method.

PubMed

Chen, Gang; Xia, Mingzhu; Lei, Wu; Wang, Fengyun; Gong, Xuedong

2013-12-01

Molecular dynamics simulations have been performed to investigate the effect of acetone solvent on the crystal morphology of RDX. The results show that the growth morphology of RDX crystal in vacuum is dominated by the (111), (020), (200), (002), and (210) faces using the BFDH laws, and (111) face is morphologically the most important. The analysis of surface structures of RDX crystal indicates that (020) face is non-polar, while (210), (111), (002), and (200) faces are polar among which (210) face has the strongest polarity. The interaction between acetone solvent and each RDX crystal face is different, and the order of binding energy on these surfaces is (210) > (111) > (002) > (200) > (020). The analysis of interactions among RDX and acetone molecules reveal that the system nonbond interactions are primary strong van der Waals and electrostatic interactions containing π-hole interactions, the weak hydrogen bond interactions are also existent. The effect of acetone on the growth of RDX crystal can be evaluated by comparing the binding energies of RDX crystalline faces. It can be predicted that compared to that in vacuum, in the process of RDX crystallization from acetone, the morphological importance of (210) face is increased more and (111) face is not the most important among RDX polar surfaces, while the non-polar (020) face probably disappears. The experimentally obtained RDX morphology grown from acetone is in agreement with the theoretical prediction.

Industrial application of ultrasound based in-line rheometry: Visualization of steady shear pipe flow of chocolate suspension in pre-crystallization process

NASA Astrophysics Data System (ADS)

Ouriev, Boris; Windhab, Erich; Braun, Peter; Zeng, Yuantong; Birkhofer, Beat

2003-12-01

In the present work an in-line ultrasonic method for investigation of the rheological flow behavior of concentrated suspensions was created. It is based on a nondestructive rheological measuring technique for pilot plant and industrial scale applications. Elsewhere the author discusses a tremendous need for in-line rheological characterization of highly concentrated suspensions exposed to pressure driven shear flow conditions. Most existing on-line methods are based on destructive macro actuators, which are not suitable for materials with sensitive to applied deformation structure. Since the process of our basic interest influences the structure of suspension it would be difficult to separate the effects of rheometric measurement and weakly pronounced structural changes arising from a fine adjustment of the process parameters. The magnitude of these effects is usually associated with the complex flow dynamics of structured liquids and is sensitive to density or temperature fluctuations around the moving rheometric actuator. Interpretation of the results of such measurements can be hindered by process parameter influences on liquid product structure. Therefore, the author introduces an in-line noninvasive rheometric method, which is implemented in a pre-crystallization process of chocolate suspension. Use of ultrasound velocity profile pressure difference (UVP-PD) technique enabled process monitoring of the chocolate pre-crystallization process. Influence of seeded crystals on Rheology of chocolate suspension was recorded and monitored on line. It was shown that even slight velocity pulsations in chocolate mainstream can strongly influence rheological properties besides influencing flow velocity profiles. Based on calculations of power law fit in raw velocity profiles and calculation of wall shear stress from pressure difference measurement, a viscosity function was calculated and monitored on line. On-line results were found to be in a good agreement with off-line data. The results of the industrial test of the UVP-PD system brought practical knowledge and stipulated further development of a Smart UVP-PD noninventive on-line rheometer.

Influence of the anions on the N-cationic benzethonium salts in the solid state and solution: Chloride, bromide, hydroxide and citrate hydrates

DOE Office of Scientific and Technical Information (OSTI.GOV)

Paradies, Henrich H., E-mail: hparadies@aol.com, E-mail: hparadies@jacobs-university.de; Jacobs University Bremen, Life Sciences and Chemistry Department, Campus Ring 1, D-28759 Bremen; Reichelt, Hendrik

The crystal structures of the hydrated cationic surfactant benzethonium (Bzth) chloride, bromide, hydroxide, and citrate have been determined by X-ray diffraction analysis and compared with their structures in solution well above their critical micelle concentration. The differences in the nature of the various anions of the four Bzth-X materials lead to unique anion environments and 3-D molecular arrangements. The water molecule in the monoclinic Bzth-Cl or Bzth-Br forms is hydrogen bonded to the halides and particularly to the hydrogens of the methoxy groups of the Bzth moiety notwithstanding the weak Brønsted acidity of the methoxy hydrogens. The citrate strongly interactsmore » with the hydrogens of the methoxy group forming an embedded anionic spherical cluster of a radius of 2.6 Å. The Bzth-OH crystallizes in a hexagonal lattice with two water molecules and reveals free water molecules forming hydrogen bonded channels through the Bzth-OH crystal along the c-axis. The distances between the cationic nitrogen and the halides are 4.04 Å and 4.20 Å, significantly longer than expected for typical van der Waals distances of 3.30 Å. The structures show weakly interacting, alternating apolar and polar layers, which run parallel to the crystallographic a-b planes or a-c planes. The Bzth-X salts were also examined in aqueous solution containing 20% (v/v) ethanol and 1.0 % (v/v) glycerol well above their critical micelle concentration by small-angle X-ray scattering (SAXS) and wide-angle X-ray scattering (WAXS). The [1,1,1] planes for the Bzth Cl or Br, the [0,0,2] and [1,1,0] planes for the Bzth-citrate, the [2,-1,0] planes and the [0,0,1] planes for the Bzth-OH found in the crystalline phase were also present in the solution phase, accordingly, the preservation of these phases are a strong indication of periodicity in the solution phase.« less

Atomic-Resolution Structure of an N(5) Flavin Adduct in D-Arginine Dehydrogenase

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fu, Guoxing; Yuan, Hongling; Wang, Siming

2011-09-06

D-Arginine dehydrogenase (DADH) catalyzes the flavin-dependent oxidative deamination of D-arginine and other D-amino acids to the corresponding imino acids. The 1.07 {angstrom} atomic-resolution structure of DADH crystallized with D-leucine unexpectedly revealed a covalent N(5) flavin adduct, instead of the expected iminoleucine product in the active site. This acyl adduct has been successfully reproduced by photoreduction of DADH in the presence of 4-methyl-2-oxopentanoic acid (ketoleucine). The iminoleucine may be released readily because of weak interactions in the binding site, in contrast to iminoarginine, converted to ketoleucine, which reacts with activated FAD to form the covalently linked acyl adduct.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pani, M., E-mail: marcella@chimica.unige.it; Institute SPIN-CNR, Corso Perrone 24, 16152 Genova; Morozkin, A.V.

The title compounds have been synthesized and characterized both from the structural and magnetic point of view. Both crystallize in a new monoclinic structure strictly related to the tetragonal BaCd{sub 11} type. The structure was solved by means of X-ray single-crystal techniques for GdNi{sub 8}Si{sub 3} and confirmed for TbNi{sub 8}Si{sub 3} on powder data; the corresponding lattice parameters (obtained from Guinier powder patterns) are a=6.3259(2), b=13.7245(5), c=7.4949(3) Å, β=113.522(3)°, V{sub cell}=596.64(3) Å{sup 3} and a=6.3200(2), b=13.6987(4), c=7.4923(2) Å, β=113.494(2)°, V{sub cell}=594.88(2) Å{sup 3}. The symmetry relationship between the tI48-I4{sub 1}/amd BaCd{sub 11} aristotype and the new ordered mS48-C2/c GdNi{submore » 8}Si{sub 3} derivative is described via the Bärnighausen formalism within the group theory. The large Gd–Gd (Tb–Tb) distances, mediated via Ni–Si network, likely lead to weak magnetic interactions. Low-field magnetization vs temperature measurements indicate weak and field-sensitive antiferromagnetic ground state, with ordering temperatures of 3 K in GdNi{sub 8}Si{sub 3} and about 2–3 K in TbNi{sub 8}Si{sub 3}. On the other hand, the isothermal field-dependent magnetization data show the presence of competing interactions in both compounds, with a field-induced ferromagnetic behavior for GdNi{sub 8}Si{sub 3} and a ferrimagnetic-like behavior in TbNi{sub 8}Si{sub 3} at the ordering temperature T{sub C/N} of about (or slightly higher than) 3K. The magnetocaloric effect, quantified in terms of isothermal magnetic entropy change ΔS{sub m}, has the maximum values of –19.8 J(kg K){sup −1} (at 4 K for 140 kOe field change) and −12.1 J(kg K){sup −1} (at 12 K for 140 kOe field change) in GdNi{sub 8}Si{sub 3} and TbNi{sub 8}Si{sub 3}, respectively. - Graphical abstract: GdNi{sub 8}Si{sub 3} and TbNi{sub 8}Si{sub 3} compounds are isostructural, and crystallize in a new monoclinic type strictly related to the tetragonal BaCd{sub 11} structure. The large R–R interatomic distances mediated via Ni–Si network lead to a weak magnetism in both compounds. - Highlights: • Novel RNi{sub 8}Si{sub 3} (R=Gd, Tb) compounds have been synthesized and characterized. • GdNi{sub 8}Si{sub 3} and TbNi{sub 8}Si{sub 3} are isostructural compounds, belonging to a new monoclinic structure type. • The monoclinic GdNi{sub 8}Si{sub 3} type is an ordered derivative of the tetragonal BaCd{sub 11} type. • The large R–R interatomic distances mediated via Ni–Si network lead to a weak magnetism. • Both compounds GdNi{sub 8}Si{sub 3} and TbNi{sub 8}Si{sub 3} show antiferromagnetic-like order around 3 K.« less

Silver(I) complexes of the weakly coordinating solvents SO(2) and CH(2)Cl(2): crystal structures, bonding, and energetics of [Ag(OSO)][Al{OC(CF(3))(3)}(4)], [Ag(OSO)(2/2)][SbF(6)], and [Ag(CH(2)Cl(2))(2)][SbF(6)].

PubMed

Decken, Andreas; Knapp, Carsten; Nikiforov, Grigori B; Passmore, Jack; Rautiainen, J Mikko; Wang, Xinping; Zeng, Xiaoqing

2009-06-22

Pushing the limits of coordination chemistry: The most weakly coordinated silver complexes of the very weakly coordinating solvents dichloromethane and liquid sulfur dioxide were prepared. Special techniques at low temperatures and the use of weakly coordinating anions allowed structural characterization of [Ag(OSO)][Al{OC(CF(3))(3)}(4)], [Ag(OSO)(2/2)][SbF(6)], and [Ag(Cl(2)CH(2))(2)][SbF(6)] (see figure). An investigation of the bonding shows that these complexes are mainly stabilized by electrostatic monopole-dipole interactions.The synthetically useful solvent-free silver(I) salt Ag[Al(pftb)(4)] (pftb=--OC(CF(3))(3)) was prepared by metathesis reaction of Li[Al(pftb)(4)] with Ag[SbF(6)] in liquid SO(2). The solvated complexes [Ag(OSO)][Al(pftb)(4)], [Ag(OSO)(2/2)][SbF(6)], and [Ag(CH(2)Cl(2))(2)][SbF(6)] were prepared and isolated by special techniques at low temperatures and structurally characterized by single-crystal X-ray diffraction. The SO(2) complexes provide the first examples of coordination of the very weak Lewis base SO(2) to silver(I). The SO(2) molecule in [Ag(OSO)][Al(pftb)(4)] is eta(1)-O coordinated to Ag(+), while the SO(2) ligands in [Ag(OSO)(2/2)][SbF(6)] bridge two Ag(+) ions in an eta(2)-O,O' (trans,trans) manner. [Ag(CH(2)Cl(2))(2)][SbF(6)] contains [Ag(CH(2)Cl(2))(2)](+) ions linked through [SbF(6)](-) ions to give a polymeric structure. The solid-state silver(I) ion affinities (SIA) of SO(2) and CH(2)Cl(2), based on bond lengths and corresponding valence units in the corresponding complexes and tensimetric titrations of Ag[Al(pftb)(4)] and Ag[SbF(6)] with SO(2) vapor, show that SO(2) is a weaker ligand to Ag(+) than the commonly used weakly coordinating solvent CH(2)Cl(2) and indicated that binding strength of SO(2) to silver(I) in the silver(I) salts increases with increasing size of the corresponding counteranion ([Al(pftb)(4)](-)>[SbF(6)](-)). The experimental findings are in good agreement with theoretical gas-phase ligand-binding energies of [Ag(L)(n)](+) (L=SO(2), CH(2)Cl(2); n=1, 2) and solid-state enthalpies obtained from Born-Fajans-Haber cycles by using the volume-based thermodynamics (VBT) approach. Bonding analysis (VB, NBO, MO) of [Ag(L)(n)](+) suggests that these complexes are almost completely stabilized by electrostatic interaction, that is, monopole-dipole interaction, with almost no covalent contribution by electron donation from the ligand orbitals into the vacant 5s orbital of Ag(+). All experimental findings and theoretical considerations demonstrate that SO(2) is less covalently bound to Ag(+) than CH(2)Cl(2) and support the thesis that SO(2) is a polar but non-coordinating solvent towards Ag(+).

GaAs Coupled Micro Resonators with Enhanced Sensitive Mass Detection

PubMed Central

Chopard, Tony; Lacour, Vivien; Leblois, Therese

2014-01-01

This work demonstrates the improvement of mass detection sensitivity and time response using a simple sensor structure. Indeed, complicated technological processes leading to very brittle sensing structures are often required to reach high sensitivity when we want to detect specific molecules in biological fields. These developments constitute an obstacle to the early diagnosis of diseases. An alternative is the design of coupled structures. In this study, the device is based on the piezoelectric excitation and detection of two GaAs microstructures vibrating in antisymmetric modes. GaAs is a crystal which has the advantage to be micromachined easily using typical clean room processes. Moreover, we showed its high potential in direct biofunctionalisation for use in the biological field. A specific design of the device was performed to improve the detection at low mass and an original detection method has been developed. The principle is to exploit the variation in amplitude at the initial resonance frequency which has in the vicinity of weak added mass the greatest slope. Therefore, we get a very good resolution for an infinitely weak mass: relative voltage variation of 8%/1 fg. The analysis is based on results obtained by finite element simulation. PMID:25474375

Cu- and Mn-bearing tourmalines from Brazil and Mozambique: crystal structures, chemistry and correlations

NASA Astrophysics Data System (ADS)

Ertl, Andreas; Giester, Gerald; Schüssler, Ulrich; Brätz, Helene; Okrusch, Martin; Tillmanns, Ekkehart; Bank, Hermann

2013-04-01

Cu- and Mn-bearing tourmalines from Brazil and Mozambique were characterised chemically (EMPA and LA-ICP-MS) and by X-ray single-crystal structure refinement. All these samples are rich in Al, Li and F (fluor-elbaite) and contain significant amounts of CuO (up to ~1.8 wt%) and MnO (up to ~3.5 wt%). Structurally investigated samples show a pronounced positive correlation between the < Y-O> distances and the (Li + Mn2+ + Cu + Fe2+) content (apfu) at this site with R 2 = 0.90. An excellent negative correlation exists between the < Y-O> distances and the Al2O3 content ( R 2 = 0.94). The samples at each locality generally show a strong negative correlation between the X-site vacancies and the (MnO + FeO) content. The Mn content in these tourmalines depends on the availability of Mn, on the formation temperature, as well as on stereochemical constraints. Because of a very weak correlation between MnO and CuO we believe that the Cu content in tourmaline is essentially dependent on the availability of Cu and on stereochemical constraints.

Synthesis, crystal structures and luminescent properties of two 4 d-4 f Ln-Ag heterometallic coordination polymers based on anion template

NASA Astrophysics Data System (ADS)

Fan, Le-Qing; Chen, Yuan; Wu, Ji-Huai; Huang, Yun-Fang

2011-04-01

Two new 4 d-4 f Ln-Ag heterometallic coordination polymers, {[ Ln3Ag 5(IN) 10(H 2O) 7]·4(ClO 4)·4(H 2O)} n ( Ln=Eu ( 1) and Sm ( 2), HIN=isonicotinic acid), have been synthesized under hydrothermal conditions by reactions of Ln2O 3, AgNO 3, HIN and HClO 4, and characterized by elemental analysis, IR, thermal analysis and single-crystal X-ray diffraction. It is proved that HClO 4 not only adjusts the pH value of the reaction mixture, but also acts as anion template. The structure determination reveals that 1 and 2 are isostructural and feature a novel two-dimensional (2D) layered hetrometallic structure constructed from one-dimensional Ln-carboxylate chains and pillared Ag(IN) 2 units. The 2D layers are further interlinked through Ag⋯Ag and Ag⋯O(ClO 4-) multiple weak interactions, which form a rare Ag-ClO 4 ribbon in lanthanide-transition metal coordination polymers, to give rise to a three-dimensional supramolecular architecture. Moreover, the luminescent properties of these two compounds have also been investigated at room temperature.

Implications of hydrogen/halogen-bond in the stabilization of confined water and anion-water clusters by a cationic receptor

NASA Astrophysics Data System (ADS)

Hoque, Md. Najbul; Das, Gopal

2016-03-01

Anion complexation of benzene capped flexible tripodal receptor and solid state stabilization of discrete hybrid anion-water or infinite water clusters by various supramolecular interactions are reported here. The crystal structure of the receptor in protonated states shows all the three arms projected in one direction. We structurally demonstrate discrete fluoride-water cluster [F2-H2O]2- and square shaped chloride-water cluster [Cl2-(H2O)2]2- inside the cationic channel of the receptor. Structural analysis also reveals that these clusters are stabilized inside the channel through active participation of N/C/Ow‧H⋯Ow, N/C/Ow‧H⋯X- (X- = F-, Cl- and I-) H-bonds and electrostatic interactions. Moreover, C-H⋯π and π⋯π types weak intermolecular interactions appear to play crucial role in supramolecular assembly of receptor. Additionally, on treatment with hydroiodic acid (HI) L resulted zwitterionic iodide complex. Crystal structure reveals the presence of S···I halogen bonded dimer, I2···I halogen bond, 1D infinite water chain and neutral iodine molecules. It is comprehensible that ligand basal structure (benzene capped and N-bridge head in two tripodal) play crucial roles in the formation of diverse halide-water cluster. All structures were well examined by different techniques such as NMR, IR, TGA, DSC, PXRD and XRD.

Quasi-two-dimensional Bose-Einstein condensation of spin triplets in the dimerized quantum magnet Ba 2 CuSi 2 O 6 Cl 2

DOE Office of Scientific and Technical Information (OSTI.GOV)

Okada, Makiko; Tanaka, Hidekazu; Kurita, Nobuyuki

We synthesized single crystals of composition Ba 2CuSi 2O 6Cl 2 and investigated their quantum magnetic properties. The crystal structure is closely related to that of the quasi-two-dimensional (2D) dimerized magnet BaCuSi 2O 6 also known as Han purple. Ba 2CuSi 2O 6Cl 2 has a singlet ground state with an excitation gap of Δ/k B = 20.8 K. The magnetization curves for two different field directions almost perfectly coincide when normalized by the g factor except for a small jump anomaly for a magnetic field perpendicular to the c axis. The magnetization curve with a nonlinear slope above themore » critical field is in excellent agreement with exact-diagonalization calculations based on a 2D coupled spin-dimer model. Individual exchange constants are also evaluated using density functional theory (DFT). The DFT results demonstrate a 2D exchange network and weak frustration between interdimer exchange interactions, supported by weak spin-lattice coupling implied from our magnetostriction data. Lastly, the magnetic-field-induced spin ordering in Ba 2CuSi 2O 6Cl 2 is described as the quasi-2D Bose-Einstein condensation of triplets.« less

Quasi-two-dimensional Bose-Einstein condensation of spin triplets in the dimerized quantum magnet Ba 2 CuSi 2 O 6 Cl 2

DOE PAGES

Okada, Makiko; Tanaka, Hidekazu; Kurita, Nobuyuki; ...

2016-09-20

We synthesized single crystals of composition Ba 2CuSi 2O 6Cl 2 and investigated their quantum magnetic properties. The crystal structure is closely related to that of the quasi-two-dimensional (2D) dimerized magnet BaCuSi 2O 6 also known as Han purple. Ba 2CuSi 2O 6Cl 2 has a singlet ground state with an excitation gap of Δ/k B = 20.8 K. The magnetization curves for two different field directions almost perfectly coincide when normalized by the g factor except for a small jump anomaly for a magnetic field perpendicular to the c axis. The magnetization curve with a nonlinear slope above themore » critical field is in excellent agreement with exact-diagonalization calculations based on a 2D coupled spin-dimer model. Individual exchange constants are also evaluated using density functional theory (DFT). The DFT results demonstrate a 2D exchange network and weak frustration between interdimer exchange interactions, supported by weak spin-lattice coupling implied from our magnetostriction data. Lastly, the magnetic-field-induced spin ordering in Ba 2CuSi 2O 6Cl 2 is described as the quasi-2D Bose-Einstein condensation of triplets.« less

Effects of strong hydrogen bonds and weak intermolecular interactions on supramolecular assemblies of 4-fluorobenzylamine

NASA Astrophysics Data System (ADS)

Wang, Shi; Ding, Xue-Hua; Li, Yong-Hua; Huang, Wei

2015-07-01

A series of supramolecular salts have been obtained by the self-assembly of 4-fluorobenzylamine and halide ions or metal chloride with 18-crown-6 as the host in the hydrochloric acid medium, i.e. (C7H9FN)+ṡX- (X = Cl-, 1; Br-, 2), [(C7H9FN)2ṡ(18-crown-6)2]2+ṡ(MCl4)2- (M = Mn, 3; Co, 5; Zn, 7; Cd, 8), [(C7H9FN)ṡ(18-crown-6)]+ṡ(FeCl4)- (4) and [(C7H9FN)ṡ(18-crown-6)]+ṡ1/2(CuCl4)2- (6). Structural analyses indicate that 1-2 crystallize in the triclinic space group P-1, 4 in orthorhombic space group Pnma and 3, 5, 6-8 in the monoclinic space group P21/c or C2/c. In these compounds, extensive intermolecular interactions have been utilized for the self-assembly of diverse supramolecular architectures, ranging from strong N-H⋯X (X = O, Cl, Br) hydrogen bonds to weak C-H⋯Y (Y = F, Cl, π) interactions. N-H⋯Cl/Br hydrogen bonds offer the major driving force in the crystal packing of salts 1-2 while N-H⋯O hydrogen bonds are found in salts 3-8.

Prediction of weak and strong topological insulators in layered semiconductors.

NASA Astrophysics Data System (ADS)

Felser, Claudia

2013-03-01

We investigate a new class of ternary materials such as LiAuSe and KHgSb with a honeycomb structure in Au-Se and Hg-Sb layers. We demonstrate the band inversion in these materials similar to HgTe, which is a strong precondition for existence of the topological surface states. In contrast with graphene, these materials exhibit strong spin-orbit coupling and a small direct band gap at the point. Since these materials are centrosymmetric, it is straightforward to determine the parity of their wave functions, and hence their topological character. Surprisingly, the compound with strong spin-orbit coupling (KHgSb) is trivial, whereas LiAuSe is found to be a topological insulator. However KHgSb is a weak topological insulators in case of an odd number of layers in the primitive unit cell. Here, the single-layered KHgSb shows a large bulk energy gap of 0.24 eV. Its side surface hosts metallic surface states, forming two anisotropic Dirac cones. Although the stacking of even-layered structures leads to trivial insulators, the structures can host a quantum spin Hall layer with a large bulk gap, if an additional single layer exists as a stacking fault in the crystal. The reported honeycomb compounds can serve as prototypes to aid in the finding of new weak topological insulators in layered small-gap semiconductors. In collaboration with Binghai Yan, Lukas Müchler, Hai-Jun Zhang, Shou-Cheng Zhang and Jürgen Kübler.

Phase transition hysteresis and anomalous Curie-Weiss behavior of ferroelectric tetragonal tungsten bronzes Ba2RETi2Nb3O15:RE=Nd,Sm

NASA Astrophysics Data System (ADS)

Prades, Marta; Beltrán, Héctor; Masó, Nahum; Cordoncillo, Eloisa; West, Anthony R.

2008-11-01

The ferroelectric tetragonal tungsten bronze (TTB) phases, Ba2RETi2Nb3O15:RE=Nd,Sm, were prepared by low temperature solvothermal synthesis. The permittivity versus temperature data of sintered ceramics show two unusual features: first, a hysteresis of 50-100 °C between values of the Curie temperature Tc on heat-cool cycles and second: a huge depression in the Curie-Weiss temperature T0. Both effects are attributed to the complex nature of their TTB-related crystal structures with different superstructures above and below Tc and the difficulty in nucleating ferroelectric domains on cooling through Tc. Several factors may contribute to the latter difficulty: first, the structures contain two sets of crystallographic sites for the "active" Ti, Nb ions; second, the distribution of Ti and Nb over these two sets of sites is not random but partially ordered; and third, below Tc a weak commensurate superstructure perpendicular to the polar c&barbelow; axis is present, but above Tc a weak incommensurate superstructure in a similar orientation is present. Hence the formation of the ferroelectric structure on cooling requires both nucleation of polar domains involving two sets of cation sites and structural change from an incommensurate to a commensurate supercell.

Crystal structure of a four-copper laccase complexed with an arylamine: insights into substrate recognition and correlation with kinetics.

PubMed

Bertrand, Thomas; Jolivalt, Claude; Briozzo, Pierre; Caminade, Eliane; Joly, Nathalie; Madzak, Catherine; Mougin, Christian

2002-06-11

Laccases are multicopper oxidases that catalyze the oxidation of a wide range of phenols or arylamines, and their use in industrial oxidative processes is increasing. We purified from the white rot fungus Trametes versicolor a laccase that exists as five different isozymes, depending on glycosylation. The 2.4 A resolution structure of the most abundant isozyme of the glycosylated enzyme was solved. The four copper atoms are present, and it is the first crystal structure of a laccase in its active form. The crystallized enzyme binds 2,5-xylidine, which was used as a laccase inducer in the fungus culture. This arylamine is a very weak reducing substrate of the enzyme. The cavity enclosing 2,5-xylidine is rather wide, allowing the accommodation of substrates of various sizes. Several amino acid residues make hydrophobic interactions with the aromatic ring of the ligand. In addition, two charged or polar residues interact with its amino group. The first one is an histidine that also coordinates the copper that functions as the primary electron acceptor. The second is an aspartate conserved among fungal laccases. The purified enzyme can oxidize various hydroxylated compounds of the phenylurea family of herbicides that we synthesized. These phenolic substrates have better affinities at pH 5 than at pH 3, which could be related to the 2,5-xylidine binding by the aspartate. This is the first high-resolution structure of a multicopper oxidase complexed to a reducing substrate. It provides a model for engineering laccases that are either more efficient or with a wider substrate specificity.

Synthesis and characterization of two layered aluminophosphates, ( T) 2HAl 2P 3O 12 ( T=2-BuNH 3+) and ( T)H 2Al 2P 3O 12 ( T=pyH +)

NASA Astrophysics Data System (ADS)

Chippindale, Ann M.; Powell, Anthony V.; Bull, Lucy M.; Jones, Richard H.; Cheetham, Anthony K.; Thomas, John M.; Xu, Ruren

1992-01-01

Two new aluminophosphates, ( T) 2HAl 2P 3O 12 ( T=2-BuNH 3+) ( I) and ( T)H 2Al 2P 3O 12 ( T=pyH +) ( II) with the same framework stoichiometry but different layer structures have been prepared under nonaqueous conditions and the structures determined by single-crystal X-ray diffraction. Compound ( I) crystallizes in the monoclinic space group P2 1/ c ( Z=4), with lattice parameters a=9.261(1) b=8.365(6), c=27.119(4) Å, β=91.50(1)δ, and V=2100.1 Å 3 ( R=0.072 and R w=0.090). The structure consists of Al-and P-centered tetrahedra linked to form layers. Protonated 2-butylamine molecules are located in the interlayer spaces and hydrogen bonded to the layers through NH 3+ groups. Weak hydrophobic van der Waals' interactions between alkyl groups of the 2-BuNH 3+ cations hold the layers together. Compound ( II) crystallizes in the triclinic space group P-1 ( Z=2), with a=8.574(2), b=8.631(3), c=10.371(2) Å, α=81.84(3), β=87.53(2), γ=69.07(2)δ, and V=709.49Å 3 ( R=0.039 and R w=0.052). The structure contains tetrahedrally coordinated P atoms and both tetrahedral and trigonal pyramidal Al atoms linked to form layers which are held together through hydrogen bonding, creating cavities in which pyH + cations reside.

Synthesis, structure and imaging of oligodeoxyribonucleotides with tellurium-nucleobase derivatization.

PubMed

Sheng, Jia; Hassan, Abdalla E A; Zhang, Wen; Zhou, Jianfeng; Xu, Bingqian; Soares, Alexei S; Huang, Zhen

2011-05-01

We report here the first synthesis of 5-phenyl-telluride-thymidine derivatives and the Te-phosphoramidite. We also report here the synthesis, structure and STM current-imaging studies of DNA oligonucleotides containing the nucleobases (thymine) derivatized with 5-phenyl-telluride functionality (5-Te). Our results show that the 5-Te-DNA is stable, and that the Te-DNA duplex has the thermo-stability similar to the corresponding native duplex. The crystal structure indicates that the 5-Te-DNA duplex structure is virtually identical to the native one, and that the Te-modified T and native A interact similarly to the native T and A pair. Furthermore, while the corresponding native showed weak signals, the DNA duplex modified with electron-rich tellurium functionality showed strong topographic and current peaks by STM imaging, suggesting a potential strategy to directly image DNA without structural perturbation. © The Author(s) 2011. Published by Oxford University Press.

Synthesis, structure and imaging of oligodeoxyribonucleotides with tellurium-nucleobase derivatization

PubMed Central

Sheng, Jia; Hassan, Abdalla E. A.; Zhang, Wen; Zhou, Jianfeng; Xu, Bingqian; Soares, Alexei S.; Huang, Zhen

2011-01-01

We report here the first synthesis of 5-phenyl–telluride–thymidine derivatives and the Te-phosphoramidite. We also report here the synthesis, structure and STM current-imaging studies of DNA oligonucleotides containing the nucleobases (thymine) derivatized with 5-phenyl-telluride functionality (5-Te). Our results show that the 5-Te-DNA is stable, and that the Te-DNA duplex has the thermo-stability similar to the corresponding native duplex. The crystal structure indicates that the 5-Te-DNA duplex structure is virtually identical to the native one, and that the Te-modified T and native A interact similarly to the native T and A pair. Furthermore, while the corresponding native showed weak signals, the DNA duplex modified with electron-rich tellurium functionality showed strong topographic and current peaks by STM imaging, suggesting a potential strategy to directly image DNA without structural perturbation. PMID:21245037

Synthesis Structure and Imaging of Oligodeoxyribonucleotides with Tellurium-nucleobase Derivatization

DOE Office of Scientific and Technical Information (OSTI.GOV)

J Sheng; A Hassan; W Zhang

2011-12-31

We report here the first synthesis of 5-phenyl-telluride-thymidine derivatives and the Te-phosphoramidite. We also report here the synthesis, structure and STM current-imaging studies of DNA oligonucleotides containing the nucleobases (thymine) derivatized with 5-phenyl-telluride functionality (5-Te). Our results show that the 5-Te-DNA is stable, and that the Te-DNA duplex has the thermo-stability similar to the corresponding native duplex. The crystal structure indicates that the 5-Te-DNA duplex structure is virtually identical to the native one, and that the Te-modified T and native A interact similarly to the native T and A pair. Furthermore, while the corresponding native showed weak signals, the DNAmore » duplex modified with electron-rich tellurium functionality showed strong topographic and current peaks by STM imaging, suggesting a potential strategy to directly image DNA without structural perturbation.« less

Synthesis, structure and imaging of oligodeoxyribonucleotides with tellurium-nucleobase derivatization

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sheng, J.; Soares, A.; Hassan, A. E. A.

2011-05-01

We report here the first synthesis of 5-phenyl-telluride-thymidine derivatives and the Te-phosphoramidite. We also report here the synthesis, structure and STM current-imaging studies of DNA oligonucleotides containing the nucleobases (thymine) derivatized with 5-phenyl-telluride functionality (5-Te). Our results show that the 5-Te-DNA is stable, and that the Te-DNA duplex has the thermo-stability similar to the corresponding native duplex. The crystal structure indicates that the 5-Te-DNA duplex structure is virtually identical to the native one, and that the Te-modified T and native A interact similarly to the native T and A pair. Furthermore, while the corresponding native showed weak signals, the DNAmore » duplex modified with electron-rich tellurium functionality showed strong topographic and current peaks by STM imaging, suggesting a potential strategy to directly image DNA without structural perturbation.« less

Time-dependent water dynamics in hydrated uranyl fluoride

DOE PAGES

Miskowiec, Andrew J.; Anderson, Brian B.; Herwig, Kenneth W.; ...

2015-09-15

In this study, uranyl fluoride is a three-layer, hexagonal structure with significant stacking disorder in the c-direction. It supports a range of unsolved ‘thermodynamic’ hydrates with 0–2.5 water molecules per uranium atom, and perhaps more. However, the relationship between water, hydrate crystal structures, and thermodynamic results, collectively representing the chemical pathway through these hydrate structures, has not been sufficiently elucidated. We used high-resolution quasielastic neutron scattering to study the dynamics of water in partially hydrated uranyl fluoride powder over the course of 4 weeks under closed conditions. The spectra are composed of two quasielastic components: one is associated with translationalmore » diffusive motion of water that is approximately five to six times slower than bulk water, and the other is a slow (on the order of 2–300 ps), spatially bounded water motion. The translational component represents water diffusing between the weakly bonded layers in the crystal, while the bounded component may represent water trapped in subnanometre ‘pockets’ formed by the space between uranium-centred polymerisation units. Complementary neutron diffraction measurements do not show any significant structural changes, suggesting that a chemical conversion of the material does not occur in the thermodynamically isolated system on this timescale.« less

Structure, magnetic properties, polarized neutron diffraction, and theoretical study of a copper(II) cubane.

PubMed

Aronica, Christophe; Chumakov, Yurii; Jeanneau, Erwann; Luneau, Dominique; Neugebauer, Petr; Barra, Anne-Laure; Gillon, Béatrice; Goujon, Antoine; Cousson, Alain; Tercero, Javier; Ruiz, Eliseo

2008-01-01

The paper reports the synthesis, X-ray and neutron diffraction crystal structures, magnetic properties, high field-high frequency EPR (HF-EPR), spin density and theoretical description of the tetranuclear CuII complex [Cu4L4] with cubane-like structure (LH2=1,1,1-trifluoro-7-hydroxy-4-methyl-5-aza-hept-3-en-2-one). The simulation of the magnetic behavior gives a predominant ferromagnetic interaction J1 (+30.5 cm(-1)) and a weak antiferromagnetic interaction J2 (-5.5 cm(-1)), which correspond to short and long Cu-Cu distances, respectively, as evidence from the crystal structure [see formulate in text]. It is in agreement with DFT calculations and with the saturation magnetization value of an S=2 ground spin state. HF-EPR measurements at low temperatures (5 to 30 K) provide evidence for a negative axial zero-field splitting parameter D (-0.25+/-0.01 cm(-1)) plus a small rhombic term E (0.025+/-0.001 cm(-1), E/D = 0.1). The experimental spin distribution from polarized neutron diffraction is mainly located in the basal plane of the CuII ion with a distortion of yz-type for one CuII ion. Delocalization on the ligand (L) is observed but to a smaller extent than expected from DFT calculations.

Against the odds? De novo structure determination of a pilin with two cysteine residues by sulfur SAD.

PubMed

Gorgel, Manuela; Bøggild, Andreas; Ulstrup, Jakob Jensen; Weiss, Manfred S; Müller, Uwe; Nissen, Poul; Boesen, Thomas

2015-05-01

Exploiting the anomalous signal of the intrinsic S atoms to phase a protein structure is advantageous, as ideally only a single well diffracting native crystal is required. However, sulfur is a weak anomalous scatterer at the typical wavelengths used for X-ray diffraction experiments, and therefore sulfur SAD data sets need to be recorded with a high multiplicity. In this study, the structure of a small pilin protein was determined by sulfur SAD despite several obstacles such as a low anomalous signal (a theoretical Bijvoet ratio of 0.9% at a wavelength of 1.8 Å), radiation damage-induced reduction of the cysteines and a multiplicity of only 5.5. The anomalous signal was improved by merging three data sets from different volumes of a single crystal, yielding a multiplicity of 17.5, and a sodium ion was added to the substructure of anomalous scatterers. In general, all data sets were balanced around the threshold values for a successful phasing strategy. In addition, a collection of statistics on structures from the PDB that were solved by sulfur SAD are presented and compared with the data. Looking at the quality indicator R(anom)/R(p.i.m.), an inconsistency in the documentation of the anomalous R factor is noted and reported.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Osiry, H.; Cano, A.; Reguera, L.

The pentacyanonitrosylferrate complex anion, [Fe(CN){sub 5}NO]{sup 2−}, forms an insoluble solid with Hg(I) ion, of formula unit Hg{sub 2}[Fe(CN){sub 5}NO]·2H{sub 2}O, whose crystal structure and related properties are unknown. This contribution reports the preparation of that compound by the precipitation method and its structural study from X-ray powder patterns complemented with spectroscopic information from IR, Raman, and UV–vis techniques. The crystal structure was solved ab initio and then refined using the Rietveld method. The solid crystallizes with a triclinic unit cell, in the P−1 space group, with cell parameters a=10.1202(12), b=10.1000(13), c=7.4704(11) Å; α=110.664(10), β=110.114(10), γ=104.724(8) °. Within the unitmore » cell, two formula units are accommodated (Z=2). It adopts a layered structure related with the coordination of the equatorial CN groups at their N end to the Hg atoms while the axial CN ligand remains unlinked. Within the layers neighboring Hg{sub 2}[Fe(CN){sub 5}NO] building units remain linked through four relatively strong Hg–Hg interactions, with an interatomic distance of 2.549(3) Å. The charge donation from the equatorial CN groups through their 5σ orbitals results into an increase for the electron density on the Hg atoms, which strengths the Hg–Hg bond. In the Raman spectrum, that metal–metal bond is detected as a stretching vibration band at 167 cm{sup −1}. The available free volume between neighboring layers accommodates two water molecules, which are stabilized within the framework through hydrogen bonds with the N end of the unlinked axial CN group. The removal of these weakly bonded water molecules results in structural disorder for the material 3D framework. - Graphical abstract: Assembling of Hg{sub 2}[Fe(CN){sub 5}NO] units through Hg–Hg interactions. - Highlights: • Homometallic Hg–Hg interactions in metal nitroprusside. • 2D structure supported on metal–metal interactions. • Crystal structure and related properties for mercury (I) nitroprusside. • IR and UV–vis spectral features for mercury (I) nitroprusside.« less

Novel red phosphors KBaEu(XO4)3 (X = Mo, W) show high color purity and high thermostability from a disordered chained structure.

PubMed

Wang, G Q; Gong, X H; Chen, Y J; Huang, J H; Lin, Y F; Luo, Z D; Huang, Y D

2017-05-23

Two novel red phosphors KBaEu(XO 4 ) 3 (X = Mo, W) have been synthesized by high-temperature solid-state reactions and the crystal structures were determined for the first time. Single-crystal X-ray diffraction data reveal that their space groups are C2/c. The crystalline structure is constituted of K/BaO 8 distorted square antiprisms and distorted EuO 8 polyhedra which form chains lying along the c-axis and two kinds of distorted XO 4 tetrahedra. This high disorder of K/Ba which might lower the crystal field symmetry around Eu 3+ results in the high purity of red emission around 615 nm originating from 5 D 0 → 7 F 2 transition under near-ultraviolet (NUV) excitation. With increasing temperature, the luminescence of KBaEu(XO 4 ) 3 (X = Mo, W) phosphors decreases almost linearly with subtle alteration for the CIE coordinate. As the temperature reaches 550 K, the red emission intensity decreases to 37.3% and 50.7% of that at 300 K for KBaEu(MoO 4 ) 3 and KBaEu(WO 4 ) 3 , respectively. The analysis of the decay curves of the 5 D 0 → 7 F 2 emission at variable temperatures indicates the weak cross relaxation and non-radiative energy transfer between Eu 3+ ions. These results demonstrate that the investigated phosphors are attractive for application in high power NUV excited white LEDs.

In-situ study of athermal reversible photocrystallization in a chalcogenide glass

NASA Astrophysics Data System (ADS)

Benekou, Vasiliki; Strizik, Lukas; Wagner, Tomas; Yannopoulos, Spyros N.; Greer, A. Lindsay; Orava, Jiri

2017-11-01

The time-resolved Raman measurements reveal a three-stage mechanism of the photostructural changes in Ge25.0Ga9.5Sb0.5S65.0 (containing 0.5 at. % of Er3+) glass under continuous-above-bandgap illumination. These changes are reversible and effectively athermal, in that the local temperature rises to about 60% of the glass-transition temperature and the phase transitions take place in the glass/crystal and not in an equilibrium liquid. In the early stages of illumination, the glassy-network dimensionality changes from a predominantly 3-D to a mixture of 2-D/1-D represented by an increase in the fraction of edge-sharing tetrahedra and the emergence of homonuclear (semi)metallic bonds. This incubation period of the structural rearrangements, weakly thermally activated with an energy of ˜0.16 eV, facilitates a reversible photocrystallization. The photocrystallization rate in the glass is comparable to that achieved by thermal crystallization from supercooled liquid at large supercooling. Almost complete re-amorphization can be achieved in about an hour by reducing the incident laser-power density by a factor of ten. Glass-ceramic composites—with varying glass-to-crystal fraction—can be obtained by ceasing the illumination during re-amorphization. Microstructural imaging reveals photoinduced mass transport and the formation of columnar-porous structures. This shows the potential for a bond-specific engineering of glassy structures for photonic applications with a spatial resolution unachievable by thermal annealing.

Dielectric relaxation of guest molecules in a clathrate structure of syndiotactic polystyrene.

PubMed

Urakawa, Osamu; Kaneko, Fumitoshi; Kobayashi, Hideo

2012-12-13

Structure and dynamics of semicrystalline polymer films composed of syndiotactic polystyrene (sPS) and 2-butanone were examined through X-ray diffraction, polarized FTIR, and dielectric relaxation measurements. The X-ray and FTIR measurements revealed its crystal structure to be δ-clathrate containing 2-butanone molecules inside. The carbonyl group of 2-butanone in the crystal was found to orient preferentially parallel to the ac plane of the crystal through the polarized ATR FTIR measurements. Dielectric measurements were also conducted on these film samples to see only the relaxation dynamics of 2-butanone thanks to the high dielectric intensity of 2-butanone compared to sPS. Two relaxation modes denoted by slow and fast modes appeared. The former was assigned to the motion of 2-butanone molecules entrapped in the cavities of the crystalline (δ-form) and the latter to those in the amorphous region. We focused on the slow mode in order to elucidate the specific dynamics of the guest molecule confined in the crystalline region. The relaxation time of the slow mode was about 4 orders of magnitude longer than that of liquid 2-butanone. This suggests that the dynamics of guest molecules is highly restricted due to the high barrier to conformational and/or orientational change of the guest molecule in the cavity of δ-crystal. Furthermore, the dielectric intensity Δε of the slow mode was much smaller than the one calculated from that of bulk liquid 2-butanone and the guest concentration in the crystalline region (the intensity was only 10% of the estimated value from the bulk liquid data). This result also indicates that the free rotational motion of 2-butanone molecules is restricted inside the crystal. This will be consistently related to the weak uniplanar orientation of the carbonyl group of 2-butanone parallel to the ac plane revealed by the X-ray and polarized ATR FTIR measurements.

Superconducting selenides intercalated with organic molecules: synthesis, crystal structure, electric and magnetic properties, superconducting properties, and phase separation in iron based-chalcogenides and hybrid organic-inorganic superconductors

NASA Astrophysics Data System (ADS)

Krzton-Maziopa, Anna; Pesko, Edyta; Puzniak, Roman

2018-06-01

Layered iron-based superconducting chalcogenides intercalated with molecular species are the subject of intensive studies, especially in the field of solid state chemistry and condensed matter physics, because of their intriguing chemistry and tunable electric and magnetic properties. Considerable progress in the research, revealing superconducting inorganic–organic hybrid materials with transition temperatures to superconducting state, T c, up to 46 K, has been brought in recent years. These novel materials are synthesized by low-temperature intercalation of molecular species, such as solvates of alkali metals and nitrogen-containing donor compounds, into layered FeSe-type structure. Both the chemical nature as well as orientation of organic molecules between the layers of inorganic host, play an important role in structural modifications and may be used for fine tuning of superconducting properties. Furthermore, a variety of donor species compatible with alkali metals, as well as the possibility of doping also in the host structure (either on Fe or Se sites), makes this system quite flexible and gives a vast array of new materials with tunable electric and magnetic properties. In this review, the main aspects of intercalation chemistry are discussed with a particular attention paid to the influence of the unique nature of intercalating species on the crystal structure and physical properties of the hybrid inorganic–organic materials. To get a full picture of these materials, a comprehensive description of the most effective chemical and electrochemical methods, utilized for synthesis of intercalated species, with critical evaluation of their strong and weak points, related to feasibility of synthesis, phase purity, crystal size and morphology of final products, is included as well.

Primary role of the electrostatic contributions in a rational growth of hysteresis loop in spin-crossover Fe(II) complexes.

PubMed

Kepenekian, Mikaël; Le Guennic, Boris; Robert, Vincent

2009-08-19

We report a comprehensive analysis of the hysteresis behavior in a series of well-characterized spin-crossover Fe(II) materials. On the basis of the available X-ray data and multireference CASSCF (complete active space self-consistent field) calculations, we show that the growth of the hysteresis loop is controlled by electrostatic contributions. These environment effects turn out to be deeply modified as the crystal structure changes along the spin transition. Our theoretical inspection demonstrates the synergy between weak bonds and electrostatic interactions in the growth of hysteresis behavior. Quantitatively, it is suggested that the electrostatic contributions significantly enhance the cooperativity factor while weak bonds are determinant in the structuration of the 3D networks. Our picture does not rely on any parametrization but uses the microscopic information to derive an expression for the cooperativity parameter. The calculated values are in very good agreement with the experimental observations. Such inspection can thus be carried out to anticipate the hysteresis behavior of this intriguing class of materials.

Quasi-one-dimensional magnetism in MnxFe1-xNb2O6 compounds: From Heisenberg to Ising chains

NASA Astrophysics Data System (ADS)

Hneda, M. L.; Oliveira Neto, S. R.; da Cunha, J. B. M.; Gusmão, M. A.; Isnard, O.

2018-06-01

A series of MnxFe1-xNb2O6 compounds (0 ⩽ x ⩽ 1) is investigated by both X-ray and neutron powder diffraction, as well as specific-heat and magnetic measurements. The samples present orthorhombic Pbcn crystal symmetry, and exhibit weakly coupled magnetic chains. These chains are of Heisenberg type (weak anisotropy) on the Mn-rich side, and Ising-like (strong anisotropy) on the Fe-rich side. Except for 100% Fe (x = 0) , which has weakly-interacting ferromagnetic Ising chains, a negative Curie-Weiss temperature is obtained from the magnetic susceptibility, indicating dominant antiferromagnetic interactions. At the lowest probed temperature, T = 1.5K , true long-range magnetic order is only observed for x = 1 , 0.8, and 0. Although the ordering is globally antiferromagnetic in all cases, the first two are characterized by a two-sublattice structure with propagation vector k = (0, 0, 0) , while the latter presents alternatingly oriented ferromagnetic chains described by k = (0,1/2, 0) . For other compositions, short-range magnetic correlations are extracted from diffuse neutron-scattering data.

Hierarchical photonic structured stimuli-responsive materials as high-performance colorimetric sensors

NASA Astrophysics Data System (ADS)

Lu, Tao; Zhu, Shenmin; Chen, Zhixin; Wang, Wanlin; Zhang, Wang; Zhang, Di

2016-05-01

Hierarchical photonic structures in nature are of special interest because they can be used as templates for fabrication of stimuli-responsive photonic crystals (PCs) with unique structures beyond man-made synthesis. The current stimuli-responsive PCs templated directly from natural PCs showed a very weak external stimuli response and poor durability due to the limitations of natural templates. Herein, we tackle this problem by chemically coating functional polymers, polyacrylamide, on butterfly wing scales which have hierarchical photonic structures. As a result of the combination of the strong water absorption properties of the polyacrylamide and the PC structures of the butterfly wing scales, the designed materials demonstrated excellent humidity responsive properties and a tremendous colour change. The colour change is induced by the refractive index change which is in turn due to the swollen nature of the polymer when the relative humidity changes. The butterfly wing scales also showed an excellent durability which is due to the chemical bonds formed between the polymer and wing scales. The synthesis strategy provides an avenue for the promising applications of stimuli-responsive PCs with hierarchical structures.Hierarchical photonic structures in nature are of special interest because they can be used as templates for fabrication of stimuli-responsive photonic crystals (PCs) with unique structures beyond man-made synthesis. The current stimuli-responsive PCs templated directly from natural PCs showed a very weak external stimuli response and poor durability due to the limitations of natural templates. Herein, we tackle this problem by chemically coating functional polymers, polyacrylamide, on butterfly wing scales which have hierarchical photonic structures. As a result of the combination of the strong water absorption properties of the polyacrylamide and the PC structures of the butterfly wing scales, the designed materials demonstrated excellent humidity responsive properties and a tremendous colour change. The colour change is induced by the refractive index change which is in turn due to the swollen nature of the polymer when the relative humidity changes. The butterfly wing scales also showed an excellent durability which is due to the chemical bonds formed between the polymer and wing scales. The synthesis strategy provides an avenue for the promising applications of stimuli-responsive PCs with hierarchical structures. Electronic supplementary information (ESI) available. See DOI: 10.1039/c6nr01875k

Synthesis, characterization and crystal structure of a 1D thiocyanato bridged [Cu(en)2Zn(NCS)4]ṡH2O. Comparison of the three structures with the same [Cu(en)2Zn(NCS)4] unit - different in structural terms

NASA Astrophysics Data System (ADS)

Wrzeszcz, Grzegorz; Muzioł, Tadeusz M.; Tereba, Natalia

2015-03-01

In this paper we report the synthesis method and the structure of a one-dimensional thiocyanato bridged heterometallic compound, [Cu(en)2Zn(NCS)4]ṡH2O (1). Moreover, we compare the structure of (1) with the previously described structures of [Cu(en)2Zn(NCS)4]ṡ0.5H2O (2) and [Cu(en)2Zn(NCS)4]ṡCH3CN (3) Pryma et al. (2003) [7]. The compound (1) has been characterized by thermal decomposition, IR, Vis and EPR spectra, and magnetic studies. Structure has been determined by X-ray analysis. Described coordination polymer crystallizes in the orthorhombic Cmcm space group with a = 12.414(2), b = 10.3276(14), c = 14.967(2) Å, α = β = γ = 90°, V = 1918.8(5) Å3 and Z = 4. Each distorted tetrahedral zinc(II) centre (with N-bonded NCS-) links two tetragonally distorted octahedral copper(II) centres by two end-to-end thiocyanato bridges and vice versa forming a zigzag type of CuZn chain. The structures of (1), (2) and (3) differ in crystallographic system, space group and/or CuZn chain type as well as in details. Variable temperature magnetic susceptibility measurements show very weak antiferromagnetic interactions between the paramagnetic copper(II) ions for compound (1).

Crystal structure and absolute configuration of (3aR,3′aR,7aS,7′aS)-2,2,2′,2′-tetra­methyl-3a,6,7,7a,3′a,6′,7′,7′a-octa­hydro-4,4′-bi[1,3-benzodioxol­yl], obtained from a Pd-catalyzed homocoupling reaction

PubMed Central

Macías, Mario A.; Pandolfi, Enrique; Schapiro, Valeria; Silveira, Gustavo P.; Vilela, Guilherme D.; Suescun, Leopoldo

2017-01-01

The absolute configuration, i.e. (3aR,3′aR,7aS,7′aS), of the title compound, C18H26O4, synthesized via a palladium-catalyzed homocoupling reaction, was determined on the basis of the synthetic pathway and was confirmed by X-ray diffraction. The homocoupled mol­ecule is formed by two chemically identical moieties built up from two five- and six-membered fused rings. The supra­molecular assembly is controlled mainly by C—H⋯O inter­actions that lead to the formation of hydrogen-bonded chains of mol­ecules along the [001] direction, while weak dipolar inter­actions and van der Waals forces hold the chains together in the crystal structure. PMID:28083142

Crystal structure of 1-iodo-3-{[4-(tert-butyl­sulfan­yl)phen­yl]ethyn­yl}azulene

PubMed Central

Förster, Sebastian; Seichter, Wilhelm; Weber, Edwin

2015-01-01

The title compound, C20H19IS, features a 1,3-disubstituted azulene involving an ethynylene elongated 4-(tert-butyl­sulfanyl)­phenyl sidearm and an iodine atom as the substituents. The azulene ring system is almost planar (r.m.s. deviation = 0.012 Å) and subtends a dihedral angle of 35.7 (1)° with the benzene ring. As a result of the inherent dipole character of the azulene core, a supra­molecular π–π dimer [separation between the centroids of the five- and seven-membered rings = 3.7632 (10) Å] with anti­parallel orientated mol­ecules can be observed in the crystal. The packing is consolidated by an unusual I⋯π(acetyl­ene) contact [I⋯Cg = 3.34 Å, C—I⋯Cg = 173.3°], and a very weak C—H⋯π inter­action is also found in the structure, with the azulene five-membered ring as the acceptor. PMID:26396788

Crystal structure of bis-[μ-(4-meth-oxy-phen-yl)methane-thiol-ato-κ(2) S:S]bis-[chlorido-(η(6)-1-isopropyl-4-methyl-benzene)-ruthenium(II)] chloro-form disolvate.

PubMed

Stíbal, David; Süss-Fink, Georg; Therrien, Bruno

2015-10-01

The mol-ecular structure of the title complex, [Ru2(C8H9OS)2Cl2(C10H14)2]·2CHCl3 or (p-MeC6H4Pr (i) )2Ru2(SCH2-p-C6H5-OCH3)2Cl2·2CHCl3, shows inversion symmetry. The two symmetry-related Ru(II) atoms are bridged by two 4-meth-oxy-α-toluene-thiol-ato [(4-meth-oxy-phen-yl)methane-thiol-ato] units. One chlorido ligand and the p-cymene ligand complete the typical piano-stool coordination environment of the Ru(II) atom. In the crystal, the CH moiety of the chloro-form mol-ecule inter-acts with the chlorido ligand of the dinuclear complex, while one Cl atom of the solvent inter-acts more weakly with the methyl group of the bridging 4-meth-oxy-α-toluene-thiol-ato unit. This assembly leads to the formation of supra-molecular chains extending parallel to [021].

Preferential deprotonation and conformational stability of dicarboxylic acids: A packing effect

NASA Astrophysics Data System (ADS)

Barooah, Nilotpal; Singh, W. Marjit; Baruah, Jubaraj B.

2008-03-01

Crystal structures of a series of salts of (6-carboxymethyl-1,3,5,7-tetraoxo-3,5,6,7-tetrahydro-1 H-pyrrolo[3,4- f]isoindol-2-yl)-acetic acid ( 1) and 2-carboxymethyl-1,3-dioxo-2,3-dihydro-1 H-isoinodole-5-carboxylic acid ( 2) with different polynuclear nitrogen containing heterocyclic compounds, namely, quinoline, 1,10-phenanthroline and 8-hydroxyquinoline are determined. In the case of salt of 1 with quinolinium and 1,10-phenanthrolinium cations syn disposition between the carboxylate anion and carboxylic acid groups is observed; whereas in the case of the 8-hydroxyquinolinium salt of 1, it is the anti disposition. It is also found that the solid state structure of 1,10-phenanthrolinium salt of 2 has deprotonation at the aromatic end, whereas in 8-hydroxy-quinolinium salt of 2 is formed by deprotonation of carboxylic acid group on the aliphatic side. The dicarboxylic acid 2 forms 1:2 co-crystals with quinoline. From crystallographic study it is shown that the weak interactions become prominent in stabilising the observed conformers and also in stabilising specific deprotonated species.

Crystal structure and magnetic properties of cyclohexylammonium trichlorocuprate(II): A quasi 1d Heisenberg S = {1}/{2} ferromagnet

NASA Astrophysics Data System (ADS)

Groenendijk, H. A.; Blöte, H. W. J.; van Duyneveldt, A. J.; Gaura, R. M.; Landee, C. P.; Willett, R. D.

1981-06-01

The crystal structure of [C 6H 11NH 3] CuCl 3, cyclohexylammonium trichlorocuprate(II) (CHAC), is orthorhombic, space group P2 12 12 1 with a = 19.441(5), b = 8.549(2) and c = 6.190(1) Å. The salt contains chains of CuCl -3 ions along the c axis. From magnetization and susceptibility measurements it is found that the compound behaves as a one-dimensional S = {1}/{2} Heisenberg ferromagnet with J1/ k = 70(2) K. Antiferromagnetic ordering with a weak ferromagnetic moment along the a axis occurs below T c = 2.18(2) K. From the metamagnetic phase diagram the interchain interactions are derived using mean field theory: z2J2/ z1J1 = 1.1 × 10 -3 and z3J3/ z1J1 = -1.0 × 10 -4. Also a small anisotropy ( J|/ J⊥ ≈ 0.01) is found in the intrachain interaction. The measurements indicate that CHAC is one of the best approximations to the 1d Heisenberg ferromagnet known to date.

Optical properties of ordered ZnO/Ag thin films on polystyrene spheres

NASA Astrophysics Data System (ADS)

Li, Xiu; Chen, Xiuyan; Xin, Zhiqing; Li, Luhai; Xu, Yanfang

2017-08-01

A thorough research of the optical properties of ZnO/Ag structures sputtered by RF on PS colloidal crystal molds with different diameters is reported. The influences of the period of the substrates on the performance of ZnO thin films were studied. The results of scanning electron microscopic, X-ray diffraction patterns and UV-vis absorption spectroscopy indicated that the ZnO/Ag thin films were well-covering on PS colloidal crystal molds. The diameter of the polystyrene particles significantly influenced the PL spectrum intensity of ZnO/Ag by affecting the interferences of light. After adding PS colloidal crystal molds with different diameters, all the samples show two luminescent regions, namely a strong, narrow UV emission peak and a wide, weak visible emission band. However, the signal of UV emission increases more significantly. In particular, the maximum enhancement occurs when the diameter is 300 nm. This work proposes an effective way to improve ZnO light emission based on a simple, rapid and cost effective method to fabricate ordered periodic substrates by preparing single layer polystyrene microspheres masks.

Investigation on Polylactide (PLA)/Poly(butylene adipate-co-terephthalate) (PBAT)/Bark Flour of Plane Tree (PF) Eco-Composites

PubMed Central

Dou, Qiang; Cai, Jun

2016-01-01

Polylactide (PLA)/poly(butylene adipate-co-terephthalate) (PBAT)/bark flour of plane tree (PF) eco-composites were prepared via melt blending. The morphologies, mechanical properties, crystal structures and melting and crystallization behaviors of the eco-composites were investigated by means of scanning electron microscopy (SEM), mechanical tests, polarized light microscopy (PLM), wide angle X-ray diffraction (WAXD) and differential scanning calorimetry (DSC), respectively. It is shown that the interfacial adhesion between PLA matrix and PF is weak and the mechanical properties of PLA/PF eco-composites are poor. The titanate treatment improves the adhesion between the matrix and the filler and enhances the stiffness of the eco-composites. The toughness is improved by PBAT and ductile fractured surfaces can be found. The spherulitic size of PLA is decreased by the addition of PF. The α crystalline form of PLA remains in the composites. Compared with PF, T-PF (PF treated by a titanate coupling agent) and PBAT have negative effects on the crystallization of PLA. PMID:28773515

A combined temperature-dependent electron and single-crystal X-ray diffraction study of the fresnoite compound Rb 2V 4+V 25+O 8

NASA Astrophysics Data System (ADS)

Withers, Ray L.; Höche, Thomas; Liu, Yun; Esmaeilzadeh, Saeid; Keding, Ralf; Sales, Brian

2004-10-01

High-purity Rb2V3O8 has been grown and temperature-dependent electron and single-crystal X-ray diffraction used to carefully investigate its fresnoite-type reciprocal lattice. In contrast to other recently investigated representatives of the fresnoite family of compounds, Rb2V3O8 is not incommensurately modulated with an incommensurate basal plane primary modulation wave vector given by q∼0.3 <110>*. A careful low-temperature electron diffraction study has, however, revealed the existence of weak incommensurate satellite reflections characterized by the primitive primary modulation wave vector q1∼0.16c*. The reciprocal space positioning of these incommensurate satellite reflections, the overall (3+1)-d superspace group symmetry, as well as the shapes of the refined displacement ellipsoids determined from single-crystal XRD refinement, are all consistent with their arising from a distinct type of condensed rigid unit modes (RUMs) of distortion of the Rb2V3O8 parent structure.

Highly crystalline inverse opal transition metal oxides via a combined assembly of soft and hard chemistries.

PubMed

Orilall, M Christopher; Abrams, Neal M; Lee, Jinwoo; DiSalvo, Francis J; Wiesner, Ulrich

2008-07-16

A combined assembly of soft and hard chemistries is employed to generate highly crystalline three-dimensionally ordered macroporous (3DOM) niobia (Nb2O5) and titania (TiO2) structures by colloidal crystal templating. Polystyrene spheres with sp2 hybridized carbon are used in a reverse-template infiltration technique based on the aqueous liquid phase deposition of the metal oxide in the interstitial spaces of a colloidal assembly. Heating under inert atmosphere as high as 900 degrees C converts the polymer into sturdy carbon that acts as a scaffold and keeps the macropores open while the oxides crystallize. Using X-ray diffraction it is demonstrated that for both oxides this approach leads to highly crystalline materials while heat treatments to lower temperatures commonly used for polymer colloidal templating, in particular for niobia, results in only weakly crystallized materials. Furthermore it is demonstrated that heat treatment directly to higher temperatures without generating the carbon scaffold leads to a collapse of the macrostructure. The approach should in principle be applicable to other 3DOM materials that require heat treatments to higher temperatures.

All-fiber mode-locked laser via short single-wall carbon nanotubes interacting with evanescent wave in photonic crystal fiber.

PubMed

Li, Yujia; Gao, Lei; Huang, Wei; Gao, Cong; Liu, Min; Zhu, Tao

2016-10-03

We report an all-fiber passively mode-locked laser based on a saturable absorber fabricated by filling short single-wall carbon nanotubes into cladding holes of grapefruit-type photonic crystal fiber. The single-wall carbon nanotube is insensitive to polarization of light for its one-dimensional structure, which suppresses the polarization dependence loss. Carbon nanotubes interact with photonic crystal fiber with ultra-weak evanescent field, which enhances the damage threshold of the saturable absorber and improves the operating stability. In our experiment, conventional soliton with a pulse duration of 1.003 ps and center wavelength of 1566.36 nm under a pump power of 240 mW is generated in a compact erbium-doped fiber laser cavity with net anomalous dispersion of -0.4102 ps². The signal to noise ratio of the fundamental frequency component is ~80 dB. The maximum average output power of the mode-locked laser reaches 9.56 mW under a pump power of 360 mW. The output power can be further improved by a higher pump power.

Incorporation of Pyrazine and Bipyridine Linkers with High-Spin Fe(II) and Co(II) in a Metal–Organic Framework

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kawamura, Airi; Greenwood, Arin R.; Filatov, Alexander S.

2017-02-27

A series of isoreticular metal organic frameworks (MOFs) of the formula M(BDC)(L) (M = Fe(II) or Co(II), BDC = 1,4-benzenedicarboxylate, L = pyrazine (pyz) or 4,4'-bipyridine (bipy)) has been synthesized and characterized by N-2 gas uptake Measurements, single crystal and powder X-ray diffraction, magnetometry, X-ray absorption spectroscopy, and Mossbauer spectroscopy. These studies indicate the formation of a permanently porous solid with high-spin Fe(II) and Co(II) centers that are weakly coupled, consistent with first-principles density functional theory calculations. This family of materials represents unusual examples of paramagnetic metal centers coordinated by linkers capable of mediating magnetic or electronic coupling in amore » porous framework. While only weak interactions are observed, the rigid 3D framework of the MOF dramatically impacts the properties of these materials when compared with close structural analogues.« less

Acoustic trapping of active matter

NASA Astrophysics Data System (ADS)

Takatori, Sho C.; de Dier, Raf; Vermant, Jan; Brady, John F.

2016-03-01

Confinement of living microorganisms and self-propelled particles by an external trap provides a means of analysing the motion and behaviour of active systems. Developing a tweezer with a trapping radius large compared with the swimmers' size and run length has been an experimental challenge, as standard optical traps are too weak. Here we report the novel use of an acoustic tweezer to confine self-propelled particles in two dimensions over distances large compared with the swimmers' run length. We develop a near-harmonic trap to demonstrate the crossover from weak confinement, where the probability density is Boltzmann-like, to strong confinement, where the density is peaked along the perimeter. At high concentrations the swimmers crystallize into a close-packed structure, which subsequently `explodes' as a travelling wave when the tweezer is turned off. The swimmers' confined motion provides a measurement of the swim pressure, a unique mechanical pressure exerted by self-propelled bodies.

Acoustic trapping of active matter

PubMed Central

Takatori, Sho C.; De Dier, Raf; Vermant, Jan; Brady, John F.

2016-01-01

Confinement of living microorganisms and self-propelled particles by an external trap provides a means of analysing the motion and behaviour of active systems. Developing a tweezer with a trapping radius large compared with the swimmers' size and run length has been an experimental challenge, as standard optical traps are too weak. Here we report the novel use of an acoustic tweezer to confine self-propelled particles in two dimensions over distances large compared with the swimmers' run length. We develop a near-harmonic trap to demonstrate the crossover from weak confinement, where the probability density is Boltzmann-like, to strong confinement, where the density is peaked along the perimeter. At high concentrations the swimmers crystallize into a close-packed structure, which subsequently ‘explodes' as a travelling wave when the tweezer is turned off. The swimmers' confined motion provides a measurement of the swim pressure, a unique mechanical pressure exerted by self-propelled bodies. PMID:26961816

Ferrocenylaniline based amide analogs of methoxybenzoic acids: Synthesis, structural characterization and butyrylcholinesterase (BChE) inhibition studies

NASA Astrophysics Data System (ADS)

Altaf, Ataf Ali; Kausar, Samia; Hamayun, Muhammad; Lal, Bhajan; Tahir, Muhammad Nawaz; Badshah, Amin

2017-10-01

Three new ferrocene based amides were synthesized with slight structural difference. The general formula of the amides is C5H5FeC5H4C6H4NHCOC6H4(OCH3). The synthesized compounds were characterized by instrumental techniques like elemental analysis, FTIR and NMR spectroscopy. Structure of the two compounds was also studied by single crystal X-rays diffraction analysis. Structural studies provide the evidence that pMeO (one of the synthesized compounds) is an example of amides having no intermolecular hydrogen bonding in solid structure. In the BChE inhibition assay, compound (oMeO) having strong intermolecular force in the solid structure is less active than the compound (pMeO) with weak intermolecular forces in the solid structure. The docking studies proved that hydrogen bonding between inhibitor and BChE enzyme is of more importance for the activity, rather than intermolecular hydrogen bonding in the solid structure of inhibitor.

Gelatin Nano-coating for Inhibiting Surface Crystallization of Amorphous Drugs.

PubMed

Teerakapibal, Rattavut; Gui, Yue; Yu, Lian

2018-01-05

Inhibit the fast surface crystallization of amorphous drugs with gelatin nano-coatings. The free surface of amorphous films of indomethacin or nifedipine was coated by a gelatin solution (type A or B) and dried. The coating's effect on surface crystallization was evaluated. Coating thickness was estimated from mass change after coating. For indomethacin (weak acid, pK a  = 4.5), a gelatin coating of either type deposited at pH 5 and 10 inhibited its fast surface crystal growth. The coating thickness was 20 ± 10 nm. A gelatin coating deposited at pH 3, however, provided no protective effect. These results suggest that an effective gelatin coating does not require that the drug and the polymer have opposite charges. The ineffective pH 3 coating might reflect the poor wetting of indomethacin's neutral, hydrophobic surface by the coating solution. For nifedipine (weak base, pK a  = 2.6), a gelatin coating of either type deposited at pH 5 inhibited its fast surface crystal growth. Gelatin nano-coatings can be conveniently applied to amorphous drugs from solution to inhibit fast surface crystallization. Unlike strong polyelectrolyte coatings, a protective gelatin coating does not require strict pairing of opposite charges. This could make gelatin coating a versatile, pharmaceutically acceptable coating for stabilizing amorphous drugs.

Synthesis of hollow ZnO microspheres by an integrated autoclave and pyrolysis process.

PubMed

Duan, Jinxia; Huang, Xintang; Wang, Enke; Ai, Hanhua

2006-03-28

Hollow zinc oxide microspheres have been synthesized from a micro ZnBr2·2H2O precursor obtained by an autoclave process in bromoform steam at 220 °C /2.5 MPa. Field-emission scanning electron microscropy (FE-SEM) and transmission electron microscopy (TEM) show that the products are about 1.0 µm single crystal spherical particles with hollow interiors, partly open surfaces and walls self-assembled by ZnO nanoparticles. X-ray diffraction (XRD) analysis shows that the as-prepared ZnO hollow spheres are of a hexagonal phase structure. A possible formation mechanism is suggested on the basis of the shape evolution of ZnO nanostructures observed by SEM and TEM. The room-temperature photoluminescence (PL) spectrum shows UV emission around 386 nm and weak green emission peaks indicating that there are few defects in the single crystal grains of the ZnO microspheres.

Weak Van der Waals Stacking, Wide-Range Band Gap, and Raman Study on Ultrathin Layers of Metal Phosphorus Trichalcogenides.

PubMed

Du, Ke-zhao; Wang, Xing-zhi; Liu, Yang; Hu, Peng; Utama, M Iqbal Bakti; Gan, Chee Kwan; Xiong, Qihua; Kloc, Christian

2016-02-23

2D semiconducting metal phosphorus trichalcogenides, particularly the bulk crystals of MPS3 (M = Fe, Mn, Ni, Cd and Zn) sulfides and MPSe3 (M = Fe and Mn) selenides, have been synthesized, crystallized and exfoliated into monolayers. The Raman spectra of monolayer FePS3 and 3-layer FePSe3 show the strong intralayer vibrations and structural stability of the atomically thin layers under ambient condition. The band gaps can be adjusted by element choices in the range of 1.3-3.5 eV. The wide-range band gaps suggest their optoelectronic applications in a broad wavelength range. The calculated cleavage energies of MPS3 are smaller than that of graphite. Therefore, the monolayers used for building of heterostructures by van der Waals stacking could be considered as the candidates for artificial 2D materials with unusual ferroelectric and magnetic properties.

Crystal structure of ochraceolide A isolated from Elaeodendron trichotomum (Turcz.) Lundell

PubMed Central

Herrera-España, Angel D.; Mena-Rejón, Gonzalo J.; Hernández-Ortega, Simón; Quijano, Leovigildo; Mirón-López, Gumersindo

2017-01-01

The title compound, C30H44O3 [systematic name: 6aR,6 bR,8aS,9aR,12aR,14bR)-4,4,6a,6;b,8a,14b-hexa­methyl-12-methyl­eneicosa­hydro-3H-phenanthro[1′,2′:6,7]indeno­[2,1-b]furan-3,11(2H)-dione], is a triterpene lactone, which was isolated from di­chloro­methane extract of Elaeodendron trichotomum (Turcz.) Lundell (celastraceae) stem bark. The compound has a lupane skeleton and consists of four fused six-membered rings and two five-membered rings. In the crystal, mol­ecules are linked by weak C—H⋯O hydrogen bonds into a three-dimensional network. The configuration of ochraceolide A was proposed based on analogue compounds which belong to the lupane type. PMID:29250361

Crystal structure of quinolinium 2-carboxy-6-nitro­benzoate monohydrate

PubMed Central

Mohana, J.; Divya Bharathi, M.; Ahila, G.; Chakkaravarthi, G.; Anbalagan, G.

2015-01-01

In the anion of the title hydrated mol­ecular salt, C9H8N+·C8H4NO6 −·H2O, the protonated carboxyl and nitro groups makes dihedral angles of 27.56 (5) and 6.86 (8)°, respectively, with the attached benzene ring, whereas the deprotonated carb­oxy group is almost orthogonal to it with a dihedral angle of 80.21 (1)°. In the crystal, the components are linked by O—H⋯O and N—H⋯O hydrogen bonds, generating [001] chains. The packing is consolidated by weak C—H⋯N and C—H⋯O inter­actions as well as aromatic π–π stacking [centroid-to-centroid distances: 3.7023 (8) & 3.6590 (9)Å] inter­actions, resulting in a three-dimensional network. PMID:25995899

Crystal structure of (2Z,5Z)-3-(4-meth­oxy­phen­yl)-2-[(4-meth­oxy­phenyl)­imino]-5-[(E)-3-(2-nitro­phen­yl)allyl­idene]-1,3-thia­zolidin-4-one

PubMed Central

Rahmani, Rachida; Djafri, Ahmed; Daran, Jean-Claude; Djafri, Ayada; Chouaih, Abdelkader; Hamzaoui, Fodil

2016-01-01

In the title compound, C26H21N3O5S, the thia­zole ring is nearly planar with a maximum deviation of 0.017 (2) Å, and is twisted with respect to the three benzene rings, making dihedral angles of 25.52 (12), 85.77 (12) and 81.85 (13)°. In the crystal, weak C—H⋯O hydrogen bonds and C—H⋯π inter­actions link the mol­ecules into a three-dimensional supra­molecular architecture. Aromatic π–π stacking is also observed between the parallel nitro­benzene rings of neighbouring mol­ecules, the centroid-to-centroid distance being 3.5872 (15) Å. PMID:26958377

Crystal structure and absolute configuration of (3aS,4S,5R,7aR)-2,2,7-trimethyl-3a,4,5,7a-tetra-hydro-1,3-benzodioxole-4,5-diol.

PubMed

Macías, Mario A; Suescun, Leopoldo; Pandolfi, Enrique; Schapiro, Valeria; Tibhe, Gaurao D; Mombrú, Álvaro W

2015-09-01

The absolute configuration of the title compound, C10H16O4, determined as 3aS,4S,5R,7aR on the basis of the synthetic pathway, was confirmed by X-ray diffraction. The mol-ecule contains a five- and a six-membered ring that adopt twisted and envelope conformations, respectively. The dihedral angle between the mean planes of the rings is 76.80 (11)° as a result of their cis-fusion. In the crystal, mol-ecules are linked by two pairs of O-H⋯O hydrogen bonds, forming chains along [010]. These chains are further connected by weaker C-H⋯O inter-actions along [100], creating (001) sheets that inter-act only by weak van der Waals forces.

Crystal structure of 3-benzamido-1-(4-nitro-benz-yl)quinolinium tri-fluoro-methane-sulfonate.

PubMed

Nicolas-Gomez, Mariana; Bazany-Rodríguez, Iván J; Plata-Vargas, Eduardo; Hernández-Ortega, Simón; Dorazco-González, Alejandro

2016-05-01

In the title compound, C23H18N3O3 (+)·CF3SO3 (-), the asymmetric unit contains two crystallographically independent organic cations with similar conformations. Each cation shows a moderate distortion between the planes of the amide groups and the quinolinium rings with dihedral angles of 14.90 (2) and 31.66 (2)°. The quinolinium and phenyl rings are slightly twisted with respect to each other at dihedral angles of 6.99 (4) and 8.54 (4)°. The tri-fluoro-methane-sulfonate anions are linked to the organic cations via N-H⋯O hydrogen-bonding inter-actions involving the NH amide groups. In the crystal, the organic cations are linked by weak C-H⋯O(nitro group) inter-actions into supramol-ecular chains propagating along the b-axis direction.

Superconducting Properties of CeIr3 Single Crystal

NASA Astrophysics Data System (ADS)

Sato, Yoshiki J.; Nakamura, Ai; Shimizu, Yusei; Maurya, Arvind; Homma, Yoshiya; Li, Dexin; Honda, Fuminori; Aoki, Dai

2018-05-01

Superconducting properties of CeIr3 single crystal with rhombohedral structure were examined for the first time using DC magnetization, specific heat, and electrical resistivity measurements. A bulk type-II superconductivity was clearly detected at Tc = 3.4 K, which is the second highest Tc among Ce-based intermetallic compounds. The thermodynamic properties as well as an upper critical field Hc2(0) ˜ 46.5 kOe for the H || c-axis are fully consistent with the weak-coupling BCS regime. The observed √{H} variation of C(H)/T becomes less pronounced upon cooling, possibly suggesting a suppression of low-energy quasiparticle excitations in an anisotropic s-wave gap in CeIr3, as observed in CeRu2. The origin of superconductivity is discussed from the viewpoints of the valence of Ce atom and Ir 5d-electron with a strong spin-orbit coupling.

Supramolecular architecture based on [Fe(CN)6]3- metallotectons and melaminium synthons

NASA Astrophysics Data System (ADS)

Krichen, Firas; Walha, Siwar; Lhoste, Jérôme; Bulou, Alain; Kabadou, Ahlem; Goutenoire, François

2017-10-01

Assembly involving [Fe(CN)6]3- metallotectons as building units and melaminium organic cation has been envisioned in order to elaborate a hybrid supramolecular based on ionic H-bonds with formula {(H-mel)4[Fe(CN)6]Cl} (H-mel+: melaminium cation). The compound has been prepared by diffusion method and characterized by single-crystal X-ray diffraction, EDX analysis, and Raman-IR spectroscopies with assignment from ab initio calculations. The melaminium exhibit self cationic coupling with cyclic hydrogen bonds to give a one dimensional {[H-mel]+}∝ synthon. Therefore, these cationic ribbons are inter-linked via hydrogen bonds by the anionic tectons [Fe(CN)6]3- and chlorine anion resulting on a 3D network. Molecular hirshfeld surfaces revealed that the crystal structure has been supported mainly by Nsbnd H⋯N and Nsbnd H⋯Cl intermolecular Hydrogen bonds and by favoured C⋯C and C⋯N weak interactions.

Biochemical and chemical characterization of trifluoromethylglyoxal bis(guanylhydrazone), a close analog of the antileukemic drug mitoguazone.

PubMed

Elo, H; Mutikainen, I

1988-01-01

In order to study the structure-activity relationships of bis(guanylhydrazone) type polyamine antimetabolites, trifluoromethylglyoxal bis(guanylhydrazone) (CF3-GBG), a close analog of the antileukemic drug methylglyoxal bis(guanylhydrazone) (mitoguazone, MGBG) was synthesized according to a novel modification of previous methods, yielding single crystals. Single-crystal X-ray crystallography revealed the presence of an isomer different from the one detected in the case of MGBG and all other bis(guanylhydrazones) so far studied. In contrast to MGBG, CF3-GBG was shown to be a very weak inhibitor of yeast adenosylmethionine decarboxylase, being thus devoid of value as a polyamine antimetabolite. In addition, the compound did not have antiproliferative activity against mouse L1210 leukemia cells in vitro. As long as analogous isomers of the two compounds are not available, no conclusions can be drawn about the reasons lying behind the drastical differences between their biological properties.

Optical Properties and Wave Propagation in Semiconductor-Based Two-Dimensional Photonic Crystals

DOE Office of Scientific and Technical Information (OSTI.GOV)

Agio, Mario

2002-12-31

This work is a theoretical investigation on the physical properties of semiconductor-based two-dimensional photonic crystals, in particular for what concerns systems embedded in planar dielectric waveguides (GaAs/AlGaAs, GaInAsP/InP heterostructures, and self-standing membranes) or based on macro-porous silicon. The photonic-band structure of photonic crystals and photonic-crystal slabs is numerically computed and the associated light-line problem is discussed, which points to the issue of intrinsic out-of-lane diffraction losses for the photonic bands lying above the light line. The photonic states are then classified by the group theory formalism: each mode is related to an irreducible representation of the corresponding small point group.more » The optical properties are investigated by means of the scattering matrix method, which numerically implements a variable-angle-reflectance experiment; comparison with experiments is also provided. The analysis of surface reflectance proves the existence of selection rules for coupling an external wave to a certain photonic mode. Such rules can be directly derived from symmetry considerations. Lastly, the control of wave propagation in weak-index contrast photonic-crystal slabs is tackled in view of designing building blocks for photonic integrated circuits. The proposed designs are found to comply with the major requirements of low-loss propagation, high and single-mode transmission. These notions are then collected to model a photonic-crystal combiner for an integrated multi-wavelength-source laser.« less

Resolving the ambiguity: Making sense of intrinsic disorder when PDB structures disagree.

PubMed

DeForte, Shelly; Uversky, Vladimir N

2016-03-01

Missing regions in X-ray crystal structures in the Protein Data Bank (PDB) have played a foundational role in the study of intrinsically disordered protein regions (IDPRs), especially in the development of in silico predictors of intrinsic disorder. However, a missing region is only a weak indication of intrinsic disorder, and this uncertainty is compounded by the presence of ambiguous regions, where more than one structure of the same protein sequence "disagrees" in terms of the presence or absence of missing residues. The question is this: are these ambiguous regions intrinsically disordered, or are they the result of static disorder that arises from experimental conditions, ensembles of structures, or domain wobbling? A novel way of looking at ambiguous regions in terms of the pattern between multiple PDB structures has been demonstrated. It was found that the propensity for intrinsic disorder increases as the level of ambiguity decreases. However, it is also shown that ambiguity is more likely to occur as the protein region is placed within different environmental conditions, and even the most ambiguous regions as a set display compositional bias that suggests flexibility. The results suggested that ambiguity is a natural result for many IDPRs crystallized under different conditions and that static disorder and wobbling domains are relatively rare. Instead, it is more likely that ambiguity arises because many of these regions were conditionally or partially disordered. © 2016 The Protein Society.

Serial millisecond crystallography of membrane and soluble protein microcrystals using synchrotron radiation

PubMed Central

Conrad, Chelsie E.; Nelson, Garrett; Stander, Natasha; Zatsepin, Nadia A.; Zook, James; Zhu, Lan; Geiger, James; Chun, Eugene; Kissick, David; Hilgart, Mark C.; Ogata, Craig; Ishchenko, Andrii; Nagaratnam, Nirupa; Roy-Chowdhury, Shatabdi; Coe, Jesse; Subramanian, Ganesh; Schaffer, Alexander; Ketwala, Gihan; Venugopalan, Nagarajan; Xu, Shenglan; Corcoran, Stephen; Ferguson, Dale; Weierstall, Uwe; Spence, John C. H.; Cherezov, Vadim; Fromme, Petra; Fischetti, Robert F.; Liu, Wei

2017-01-01

Crystal structure determination of biological macromolecules using the novel technique of serial femtosecond crystallography (SFX) is severely limited by the scarcity of X-ray free-electron laser (XFEL) sources. However, recent and future upgrades render microfocus beamlines at synchrotron-radiation sources suitable for room-temperature serial crystallography data collection also. Owing to the longer exposure times that are needed at synchrotrons, serial data collection is termed serial millisecond crystallography (SMX). As a result, the number of SMX experiments is growing rapidly, with a dozen experiments reported so far. Here, the first high-viscosity injector-based SMX experiments carried out at a US synchrotron source, the Advanced Photon Source (APS), are reported. Microcrystals (5–20 µm) of a wide variety of proteins, including lysozyme, thaumatin, phycocyanin, the human A2A adenosine receptor (A2AAR), the soluble fragment of the membrane lipoprotein Flpp3 and proteinase K, were screened. Crystals suspended in lipidic cubic phase (LCP) or a high-molecular-weight poly(ethylene oxide) (PEO; molecular weight 8 000 000) were delivered to the beam using a high-viscosity injector. In-house data-reduction (hit-finding) software developed at APS as well as the SFX data-reduction and analysis software suites Cheetah and CrystFEL enabled efficient on-site SMX data monitoring, reduction and processing. Complete data sets were collected for A2AAR, phycocyanin, Flpp3, proteinase K and lysozyme, and the structures of A2AAR, phycocyanin, proteinase K and lysozyme were determined at 3.2, 3.1, 2.65 and 2.05 Å resolution, respectively. The data demonstrate the feasibility of serial millisecond crystallography from 5–20 µm crystals using a high-viscosity injector at APS. The resolution of the crystal structures obtained in this study was dictated by the current flux density and crystal size, but upcoming developments in beamline optics and the planned APS-U upgrade will increase the intensity by two orders of magnitude. These developments will enable structure determination from smaller and/or weakly diffracting microcrystals. PMID:28875031

Serial millisecond crystallography of membrane and soluble protein microcrystals using synchrotron radiation.

PubMed

Martin-Garcia, Jose M; Conrad, Chelsie E; Nelson, Garrett; Stander, Natasha; Zatsepin, Nadia A; Zook, James; Zhu, Lan; Geiger, James; Chun, Eugene; Kissick, David; Hilgart, Mark C; Ogata, Craig; Ishchenko, Andrii; Nagaratnam, Nirupa; Roy-Chowdhury, Shatabdi; Coe, Jesse; Subramanian, Ganesh; Schaffer, Alexander; James, Daniel; Ketwala, Gihan; Venugopalan, Nagarajan; Xu, Shenglan; Corcoran, Stephen; Ferguson, Dale; Weierstall, Uwe; Spence, John C H; Cherezov, Vadim; Fromme, Petra; Fischetti, Robert F; Liu, Wei

2017-07-01

Crystal structure determination of biological macromolecules using the novel technique of serial femtosecond crystallography (SFX) is severely limited by the scarcity of X-ray free-electron laser (XFEL) sources. However, recent and future upgrades render microfocus beamlines at synchrotron-radiation sources suitable for room-temperature serial crystallography data collection also. Owing to the longer exposure times that are needed at synchrotrons, serial data collection is termed serial millisecond crystallography (SMX). As a result, the number of SMX experiments is growing rapidly, with a dozen experiments reported so far. Here, the first high-viscosity injector-based SMX experiments carried out at a US synchrotron source, the Advanced Photon Source (APS), are reported. Microcrystals (5-20 µm) of a wide variety of proteins, including lysozyme, thaumatin, phycocyanin, the human A 2A adenosine receptor (A 2A AR), the soluble fragment of the membrane lipoprotein Flpp3 and proteinase K, were screened. Crystals suspended in lipidic cubic phase (LCP) or a high-molecular-weight poly(ethylene oxide) (PEO; molecular weight 8 000 000) were delivered to the beam using a high-viscosity injector. In-house data-reduction (hit-finding) software developed at APS as well as the SFX data-reduction and analysis software suites Cheetah and CrystFEL enabled efficient on-site SMX data monitoring, reduction and processing. Complete data sets were collected for A 2A AR, phycocyanin, Flpp3, proteinase K and lysozyme, and the structures of A 2A AR, phycocyanin, proteinase K and lysozyme were determined at 3.2, 3.1, 2.65 and 2.05 Å resolution, respectively. The data demonstrate the feasibility of serial millisecond crystallography from 5-20 µm crystals using a high-viscosity injector at APS. The resolution of the crystal structures obtained in this study was dictated by the current flux density and crystal size, but upcoming developments in beamline optics and the planned APS-U upgrade will increase the intensity by two orders of magnitude. These developments will enable structure determination from smaller and/or weakly diffracting microcrystals.

Multinuclear Solid-State Magnetic Resonance as a Sensitive Probe of Structural Changes upon the Occurrence of Halogen Bonding in Co-crystals.

PubMed

Widdifield, Cory M; Cavallo, Gabriella; Facey, Glenn A; Pilati, Tullio; Lin, Jingxiang; Metrangolo, Pierangelo; Resnati, Giuseppe; Bryce, David L

2013-09-02

Although the understanding of intermolecular interactions, such as hydrogen bonding, is relatively well-developed, many additional weak interactions work both in tandem and competitively to stabilize a given crystal structure. Due to a wide array of potential applications, a substantial effort has been invested in understanding the halogen bond. Here, we explore the utility of multinuclear ((13)C, (14/15)N, (19)F, and (127)I) solid-state magnetic resonance experiments in characterizing the electronic and structural changes which take place upon the formation of five halogen-bonded co-crystalline product materials. Single-crystal X-ray diffraction (XRD) structures of three novel co-crystals which exhibit a 1:1 stoichiometry between decamethonium diiodide (i.e., [(CH3)3N(+)(CH2)10N(+)(CH3)3][2 I(-)]) and different para-dihalogen-substituted benzene moieties (i.e., p-C6X2Y4, X=Br, I; Y=H, F) are presented. (13)C and (15)N NMR experiments carried out on these and related systems validate sample purity, but also serve as indirect probes of the formation of a halogen bond in the co-crystal complexes in the solid state. Long-range changes in the electronic environment, which manifest through changes in the electric field gradient (EFG) tensor, are quantitatively measured using (14)N NMR spectroscopy, with a systematic decrease in the (14)N quadrupolar coupling constant (CQ) observed upon halogen bond formation. Attempts at (127)I solid-state NMR spectroscopy experiments are presented and variable-temperature (19)F NMR experiments are used to distinguish between dynamic and static disorder in selected product materials, which could not be conclusively established using solely XRD. Quantum chemical calculations using the gauge-including projector augmented-wave (GIPAW) or relativistic zeroth-order regular approximation (ZORA) density functional theory (DFT) approaches complement the experimental NMR measurements and provide theoretical corroboration for the changes in NMR parameters observed upon the formation of a halogen bond. Copyright © 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim.

Structure of complex of N-methylpiperidine betaine with p-hydroxybenzoic acid studied by X-ray, FT-IR and DFT methods

NASA Astrophysics Data System (ADS)

Dega-Szafran, Z.; Dutkiewicz, G.; Kosturkiewicz, Z.; Szafran, M.

2008-03-01

Crystal structure of the complex of N-methylpiperidine betaine ( N-carboxymethyl- N-methylpiperidinium inner salt, MPB) with p-hydroxybenzoic acid (HBA) has been determined by X-ray diffraction. The crystals are triclinic, space group Pī, with a = 6.1156(5), b = 10.6869(10), c = 12.0320(10) Å, α = 109.55(1)°, β = 95.25(1)°, γ = 99.22(1)°, Z = 2, R = 0.034. Two molecules of p-hydroxybenzoic acid and two molecules of N-methylpiperidine betaine are linked together forming a centrosymmetric dimer, (MPB·HBA) 2, by four O-H···O hydrogen bonds of lengths 2.622(1) and 2.617(1) Å, between the carboxylic and hydroxy groups of HBA and both oxygen atoms of the carboxylate group of MPB, respectively. The piperidine ring has a chair conformation with the CH 2COO - substituent in the axial position and the CH 3 group in the equatorial one. Two parallel aromatic rings in (MPB·HBA) 2 are distanced by 3.457 Å. In the crystals the complexes form "islands" related to the neighboring complexes by the inversion centers, weak C-H···O bonds and van der Waals forces. A broad band in the 3100-2400 cm -1 region and two bands attributed to the νC dbnd O (1689 cm -1) and νasCOO (1607 cm -1) vibrations in the FT-IR spectrum confirm the structure of the title complex. The two structures of MPB·HBA, denoted as A and B, have been optimized by the B3LYP/6-31G(d,p) method. In A, MPB forms a O-H···O hydrogen bond (2.562 Å) with the carboxylic group of HBA shorter than in the crystals, while in B it interacts with the phenolic group of HBA by a longer O-H···O hydrogen bond (2.661 Å) than in the crystals. Complex A is slightly more stable than B (0.15 kcal/mol).

Serial millisecond crystallography of membrane and soluble protein microcrystals using synchrotron radiation

DOE PAGES

Martin-Garcia, Jose M.; Conrad, Chelsie E.; Nelson, Garrett; ...

2017-05-24

Crystal structure determination of biological macromolecules using the novel technique of serial femtosecond crystallography (SFX) is severely limited by the scarcity of X-ray free-electron laser (XFEL) sources. However, recent and future upgrades render microfocus beamlines at synchrotron-radiation sources suitable for room-temperature serial crystallography data collection also. Owing to the longer exposure times that are needed at synchrotrons, serial data collection is termed serial millisecond crystallography (SMX). As a result, the number of SMX experiments is growing rapidly, with a dozen experiments reported so far. Here, the first high-viscosity injector-based SMX experiments carried out at a US synchrotron source, the Advancedmore » Photon Source (APS), are reported. Microcrystals (5–20 µm) of a wide variety of proteins, including lysozyme, thaumatin, phycocyanin, the human A 2A adenosine receptor (A 2AAR), the soluble fragment of the membrane lipoprotein Flpp3 and proteinase K, were screened. Crystals suspended in lipidic cubic phase (LCP) or a high-molecular-weight poly(ethylene oxide) (PEO; molecular weight 8 000 000) were delivered to the beam using a high-viscosity injector. In-house data-reduction (hit-finding) software developed at APS as well as the SFX data-reduction and analysis software suites Cheetah and CrystFEL enabled efficient on-site SMX data monitoring, reduction and processing. Complete data sets were collected for A 2AAR, phycocyanin, Flpp3, proteinase K and lysozyme, and the structures of A 2AAR, phycocyanin, proteinase K and lysozyme were determined at 3.2, 3.1, 2.65 and 2.05 Å resolution, respectively. The data demonstrate the feasibility of serial millisecond crystallography from 5–20 µm crystals using a high-viscosity injector at APS. The resolution of the crystal structures obtained in this study was dictated by the current flux density and crystal size, but upcoming developments in beamline optics and the planned APS-U upgrade will increase the intensity by two orders of magnitude. Furthermore, these developments will enable structure determination from smaller and/or weakly diffracting microcrystals.« less

Serial millisecond crystallography of membrane and soluble protein microcrystals using synchrotron radiation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Martin-Garcia, Jose M.; Conrad, Chelsie E.; Nelson, Garrett

Crystal structure determination of biological macromolecules using the novel technique of serial femtosecond crystallography (SFX) is severely limited by the scarcity of X-ray free-electron laser (XFEL) sources. However, recent and future upgrades render microfocus beamlines at synchrotron-radiation sources suitable for room-temperature serial crystallography data collection also. Owing to the longer exposure times that are needed at synchrotrons, serial data collection is termed serial millisecond crystallography (SMX). As a result, the number of SMX experiments is growing rapidly, with a dozen experiments reported so far. Here, the first high-viscosity injector-based SMX experiments carried out at a US synchrotron source, the Advancedmore » Photon Source (APS), are reported. Microcrystals (5–20 µm) of a wide variety of proteins, including lysozyme, thaumatin, phycocyanin, the human A 2A adenosine receptor (A 2AAR), the soluble fragment of the membrane lipoprotein Flpp3 and proteinase K, were screened. Crystals suspended in lipidic cubic phase (LCP) or a high-molecular-weight poly(ethylene oxide) (PEO; molecular weight 8 000 000) were delivered to the beam using a high-viscosity injector. In-house data-reduction (hit-finding) software developed at APS as well as the SFX data-reduction and analysis software suites Cheetah and CrystFEL enabled efficient on-site SMX data monitoring, reduction and processing. Complete data sets were collected for A 2AAR, phycocyanin, Flpp3, proteinase K and lysozyme, and the structures of A 2AAR, phycocyanin, proteinase K and lysozyme were determined at 3.2, 3.1, 2.65 and 2.05 Å resolution, respectively. The data demonstrate the feasibility of serial millisecond crystallography from 5–20 µm crystals using a high-viscosity injector at APS. The resolution of the crystal structures obtained in this study was dictated by the current flux density and crystal size, but upcoming developments in beamline optics and the planned APS-U upgrade will increase the intensity by two orders of magnitude. Furthermore, these developments will enable structure determination from smaller and/or weakly diffracting microcrystals.« less

Peak effect in untwinned YBa 2Cu 3O 7-δ single crystals

NASA Astrophysics Data System (ADS)

D'Anna, G.; André, M.-O.; Indenbom, M. V.; Benoit, W.

1994-12-01

We report on the observation of a weak effect of the critical current density in untwinned YBa 2Cu 3O 7-δ single crystals of different purity, using a low frequency torsion pendulum. We construct the peak effect line and the irreversibility line.

A new method for solid surface topographical studies using nematic liquid crystals

NASA Astrophysics Data System (ADS)

Baber, N.; Strugalski, Z.

1984-03-01

A new simple method has been developed to investigate the topography of a wide range of solid surfaces using nematic liquid crystals. Polarizing microscopy is employed. The usefulness of the method for detecting weak mechanical effects has been demonstrated. An application in criminology is foreseen.

Crystal structures of the three closely related compounds: bis-[(1H-tetra-zol-5-yl)meth-yl]nitramide, tri-amino-guanidinium 5-({[(1H-tetra-zol-5-yl)meth-yl](nitro)-amino}-meth-yl)tetra-zol-1-ide, and di-ammonium bis-[(tetra-zol-1-id-5-yl)meth-yl]nitramide monohydrate.

PubMed

Mitchell, Lauren A; Imler, Gregory H; Parrish, Damon A; Deschamps, Jeffrey R; Leonard, Philip W; Chavez, David E

2017-07-01

In the mol-ecule of neutral bis-[(1 H -tetra-zol-5-yl)meth-yl]nitramide, (I), C 4 H 6 N 10 O 2 , there are two intra-molecular N-H⋯O hydrogen bonds. In the crystal, N-H⋯N hydrogen bonds link mol-ecules, forming a two-dimensional network parallel to (-201) and weak C-H⋯O, C-H⋯N hydrogen bonds, and inter-molecular π-π stacking completes the three-dimensional network. The anion in the molecular salt, tri-amino-guanidinium 5-({[(1 H -tetra-zol-5-yl)meth-yl](nitro)-amino}-meth-yl)tetra-zol-1-ide, (II), CH 9 N 6 + ·C 4 H 5 N 10 O 2 - , displays intra-molecular π-π stacking and in the crystal, N-H⋯N and N-H⋯O hydrogen bonds link the components of the structure, forming a three-dimensional network. In the crystal of di-ammonium bis-[(tetra-zol-1-id-5-yl)meth-yl]nitramide monohydrate, (III), 2NH 4 + ·C 4 H 4 N 10 O 2 2- ·H 2 O, O-H⋯N, N-H⋯N, and N-H⋯O hydrogen bonds link the components of the structure into a three-dimensional network. In addition, there is inter-molecular π-π stacking. In all three structures, the central N atom of the nitramide is mainly sp 2 -hybridized. Bond lengths indicate delocalization of charges on the tetra-zole rings for all three compounds. Compound (II) was found to be a non-merohedral twin and was solved and refined in the major component.

Arizona porphyry copper/hydrothermal deposits II: Crystal structure of ajoite, (K + Na)3Cu20Al3Si29O76(OH)16⋅∼8H2O

PubMed Central

Pluth, Joseph J.; Smith, Joseph V.

2002-01-01

A crystal from the type locality Ajo, AZ, yielded just enough intensity from streaked diffractions using synchrotron x-rays at the Advanced Photon Source to solve the crystal structure with composition (K + Na)3Cu20Al3Si29O76(OH)16⋅∼8H2O; triclinic, P1̄, a = 13.634(5) Å, b = 13.687(7), c = 14.522(7), α = 110.83(1)°, β = 107.21(1), γ = 105.68(1); refined to a final R = 12.5%. Electron microprobe analysis yielded a similar chemical composition that is slightly different from the combined chemical and electron microprobe analyses in the literature. The ajoite structure can be described as a zeolitic octahedral-tetrahedral framework that combines the alternate stacking of edge-sharing octahedral CuO6 layers and curved aluminosilicate layers and strings. Channels bounded by elliptical 12-rings and circular 8-rings of tetrahedra contain (K and Na) ions and water. The Al atoms occupy some of the Si tetrahedral sites. Each Cu atom has near-planar bonds to four oxygen atoms plus two longer distances that generate a distorted octahedron. Valence bond estimates indicate that 8 oxygen atoms of 46 are hydroxyl. Only one alkali atom was located in distorted octahedral coordination, and electron microprobe analyses indicate K and Na as major substituents. The water from chemical analysis presumably occurs as disordered molecules of zeolitic type not giving electron density from diffraction. The high R factor results from structural disorder and many weak intensities close to detection level. The crystal chemistry is compared with shattuckite, Cu5(SiO3)4(OH)2, and planchéite, Cu8Si8O22(OH)4⋅H2O, both found in oxidized copper deposits of Arizona but only the former directly with ajoite. PMID:12177404

Arizona porphyry copper/hydrothermal deposits II: crystal structure of ajoite, (K + Na)3Cu20Al3Si29O76(OH)16*~8H2O.

PubMed

Pluth, Joseph J; Smith, Joseph V

2002-08-20

A crystal from the type locality Ajo, AZ, yielded just enough intensity from streaked diffractions using synchrotron x-rays at the Advanced Photon Source to solve the crystal structure with composition (K + Na)3Cu20Al3Si29O76(OH)16* approximately 8H2O; triclinic, P1, a = 13.634(5) A, b = 13.687(7), c = 14.522(7), alpha = 110.83(1) degrees, beta = 107.21(1), gamma = 105.68(1); refined to a final R = 12.5%. Electron microprobe analysis yielded a similar chemical composition that is slightly different from the combined chemical and electron microprobe analyses in the literature. The ajoite structure can be described as a zeolitic octahedral-tetrahedral framework that combines the alternate stacking of edge-sharing octahedral CuO6 layers and curved aluminosilicate layers and strings. Channels bounded by elliptical 12-rings and circular 8-rings of tetrahedra contain (K and Na) ions and water. The Al atoms occupy some of the Si tetrahedral sites. Each Cu atom has near-planar bonds to four oxygen atoms plus two longer distances that generate a distorted octahedron. Valence bond estimates indicate that 8 oxygen atoms of 46 are hydroxyl. Only one alkali atom was located in distorted octahedral coordination, and electron microprobe analyses indicate K and Na as major substituents. The water from chemical analysis presumably occurs as disordered molecules of zeolitic type not giving electron density from diffraction. The high R factor results from structural disorder and many weak intensities close to detection level. The crystal chemistry is compared with shattuckite, Cu5(SiO3)4(OH)2, and planchéite, Cu8Si8O22(OH)4.H2O, both found in oxidized copper deposits of Arizona but only the former directly with ajoite.

Synthesis and Structural Studies of Calcium and Magnesium Phosphinate and Phosphonate Compounds

NASA Astrophysics Data System (ADS)

Bampoh, Victoria Naa Kwale

The work presented herein describes synthetic methodologies leading to the design of a wide array of magnesium and calcium based phosphinate and phosphonates with possible applications as bone scaffolding materials or additives to bone cements. The challenge to the chemistry of the alkaline earth phosphonate target compounds includes poor solubility of compounds, and poorly understood details on the control of the metal's coordination environment. Hence, less is known on phosphonate based alkaline earth metal organic frameworks as compared to transition metal phosphonates. Factors governing the challenges in obtaining crystalline, well-defined magnesium and calcium solids lie in the large metal diameters, the absence of energetically available d-orbitals to direct metal geometry, as well as the overall weakness of the metal-ligand bonds. A significant part of this project was concerned with the development of suitable reaction conditions to obtain X-ray quality crystals of the reaction products to allow for structural elucidation of the novel compounds. Various methodologies to aid in crystal growth including hydrothermal methods and gel crystallization were employed. We have used phosphinate and phosphonate ligands with different number of phosphorus oxygen atoms as well as diphosphonates with different linker lengths to determine their effects on the overall structural features. An interesting correlation is observed between the dimensionality of products and the increasing number of donor oxygen atoms in the ligands as we progress from phosphinic acid to the phosphorous acids. As an example, monophosphinate ligand only yielded one-dimensional compounds, whereas the phosphonates crystallize as one and two-dimensional compounds, and the di- and triphosphonate based compounds display two or three-dimensional geometries. This thesis provides a selection of calcium and magnesium compounds with one-dimensional geometry, as represented in a calcium phosphinate to novel two-dimensional sheets of magnesium and pillared calcium phosphonates. The preparation of these novel compounds has led to the establishment of synthetic protocols that allow for the direct preparation of compounds with defined structural features.

Crystal structures of seven molecular salts derived from benzylamine and organic acidic components

NASA Astrophysics Data System (ADS)

Wen, Xianhong; Jin, Xiunan; Lv, Chengcai; Jin, Shouwen; Zheng, Xiuqing; Liu, Bin; Wang, Daqi; Guo, Ming; Xu, Weiqiang

2017-07-01

Cocrystallization of the commonly available organic amine, benzylamine, with a series of organic acids gave a total of seven molecular salts with the compositions: (benzylamine): (p-toluenesulfonic acid) (1) [(HL)+ · (tsa-)], (benzylamine): (o-nitrobenzoic acid) (2) [(HL+) · (onba)-], (benzylamine): (3,4-methylenedioxybenzoic acid) (3) [(HL+) · (mdba-)], (benzylamine): (mandelic acid) (4) [(HL+) · (mda-)], (benzylamine): (5-bromosalicylic acid)2(5) [(HL+) · (bsac-) · (Hbsac)], (benzylamine): (m-phthalic acid) (6) [(HL+) · (Hmpta-)], and (benzylamine)2: (trimesic acid) (7) [(HL+)2 · (Htma2-)]. The seven salts have been characterised by X-ray diffraction technique, IR, and elemental analysis, and the melting points of all the salts were also reported. And their structural and supramolecular aspects are fully analyzed. The result reveals that among the seven investigated crystals the NH2 groups in the benzylamine moieties are protonated when the organic acids are deprotonated, and the crystal packing is interpreted in terms of the strong charge-assisted Nsbnd H⋯O hydrogen bond formation between the ammonium and the deprotonated acidic groups. Except the Nsbnd H⋯O hydrogen bond, the Osbnd H⋯O hydrogen bonds (charge assisted or neutral) were also found at the salts 4-7. Further analysis of the crystal packing of the salts indicated that a different family of additional CHsbnd O/CH2sbnd O, CHsbnd π/CH2sbnd π, Osbnd O, and Osbnd Cπ associations contribute to the stabilization and expansion of the total high-dimensional (2D-3D) framework structures. For the coexistence of the various weak nonbonding interactions these structures adopted homo or hetero supramolecular synthons or both. Some classical supramolecular synthons, such as R42(8), R43(10) and R44(12), usually observed in organic solids of organic acids with amine, were again shown to be involved in constructing most of these hydrogen bonding networks.

Scalable solution-phase epitaxial growth of symmetry-mismatched heterostructures on two-dimensional crystal soft template.

PubMed

Lin, Zhaoyang; Yin, Anxiang; Mao, Jun; Xia, Yi; Kempf, Nicholas; He, Qiyuan; Wang, Yiliu; Chen, Chih-Yen; Zhang, Yanliang; Ozolins, Vidvuds; Ren, Zhifeng; Huang, Yu; Duan, Xiangfeng

2016-10-01

Epitaxial heterostructures with precisely controlled composition and electronic modulation are of central importance for electronics, optoelectronics, thermoelectrics, and catalysis. In general, epitaxial material growth requires identical or nearly identical crystal structures with small misfit in lattice symmetry and parameters and is typically achieved by vapor-phase depositions in vacuum. We report a scalable solution-phase growth of symmetry-mismatched PbSe/Bi 2 Se 3 epitaxial heterostructures by using two-dimensional (2D) Bi 2 Se 3 nanoplates as soft templates. The dangling bond-free surface of 2D Bi 2 Se 3 nanoplates guides the growth of PbSe crystal without requiring a one-to-one match in the atomic structure, which exerts minimal restriction on the epitaxial layer. With a layered structure and weak van der Waals interlayer interaction, the interface layer in the 2D Bi 2 Se 3 nanoplates can deform to accommodate incoming layer, thus functioning as a soft template for symmetry-mismatched epitaxial growth of cubic PbSe crystal on rhombohedral Bi 2 Se 3 nanoplates. We show that a solution chemistry approach can be readily used for the synthesis of gram-scale PbSe/Bi 2 Se 3 epitaxial heterostructures, in which the square PbSe (001) layer forms on the trigonal/hexagonal (0001) plane of Bi 2 Se 3 nanoplates. We further show that the resulted PbSe/Bi 2 Se 3 heterostructures can be readily processed into bulk pellet with considerably suppressed thermal conductivity (0.30 W/m·K at room temperature) while retaining respectable electrical conductivity, together delivering a thermoelectric figure of merit ZT three times higher than that of the pristine Bi 2 Se 3 nanoplates at 575 K. Our study demonstrates a unique epitaxy mode enabled by the 2D nanocrystal soft template via an affordable and scalable solution chemistry approach. It opens up new opportunities for the creation of diverse epitaxial heterostructures with highly disparate structures and functions.

Scalable solution-phase epitaxial growth of symmetry-mismatched heterostructures on two-dimensional crystal soft template

PubMed Central

Lin, Zhaoyang; Yin, Anxiang; Mao, Jun; Xia, Yi; Kempf, Nicholas; He, Qiyuan; Wang, Yiliu; Chen, Chih-Yen; Zhang, Yanliang; Ozolins, Vidvuds; Ren, Zhifeng; Huang, Yu; Duan, Xiangfeng

2016-01-01

Epitaxial heterostructures with precisely controlled composition and electronic modulation are of central importance for electronics, optoelectronics, thermoelectrics, and catalysis. In general, epitaxial material growth requires identical or nearly identical crystal structures with small misfit in lattice symmetry and parameters and is typically achieved by vapor-phase depositions in vacuum. We report a scalable solution-phase growth of symmetry-mismatched PbSe/Bi2Se3 epitaxial heterostructures by using two-dimensional (2D) Bi2Se3 nanoplates as soft templates. The dangling bond–free surface of 2D Bi2Se3 nanoplates guides the growth of PbSe crystal without requiring a one-to-one match in the atomic structure, which exerts minimal restriction on the epitaxial layer. With a layered structure and weak van der Waals interlayer interaction, the interface layer in the 2D Bi2Se3 nanoplates can deform to accommodate incoming layer, thus functioning as a soft template for symmetry-mismatched epitaxial growth of cubic PbSe crystal on rhombohedral Bi2Se3 nanoplates. We show that a solution chemistry approach can be readily used for the synthesis of gram-scale PbSe/Bi2Se3 epitaxial heterostructures, in which the square PbSe (001) layer forms on the trigonal/hexagonal (0001) plane of Bi2Se3 nanoplates. We further show that the resulted PbSe/Bi2Se3 heterostructures can be readily processed into bulk pellet with considerably suppressed thermal conductivity (0.30 W/m·K at room temperature) while retaining respectable electrical conductivity, together delivering a thermoelectric figure of merit ZT three times higher than that of the pristine Bi2Se3 nanoplates at 575 K. Our study demonstrates a unique epitaxy mode enabled by the 2D nanocrystal soft template via an affordable and scalable solution chemistry approach. It opens up new opportunities for the creation of diverse epitaxial heterostructures with highly disparate structures and functions. PMID:27730211

Mechanisms and efficiency of the simultaneous removal of metals and cyanides by using ferrate(VI): crucial roles of nanocrystalline iron(III) oxyhydroxides and metal carbonates.

PubMed

Filip, Jan; Yngard, Ria A; Siskova, Karolina; Marusak, Zdenek; Ettler, Vojtech; Sajdl, Petr; Sharma, Virender K; Zboril, Radek

2011-08-29

The reaction of potassium ferrate(VI), K(2)FeO(4), with weak-acid dissociable cyanides--namely, K(2)[Zn(CN)(4)], K(2)[Cd(CN)(4)], K(2)[Ni(CN)(4)], and K(3)[Cu(CN)(4)]--results in the formation of iron(III) oxyhydroxide nanoparticles that differ in size, crystal structure, and surface area. During cyanide oxidation and the simultaneous reduction of iron(VI), zinc(II), copper(II), and cadmium(II), metallic ions are almost completely removed from solution due to their coprecipitation with the iron(III) oxyhydroxides including 2-line ferrihydrite, 7-line ferrihydrite, and/or goethite. Based on the results of XRD, Mössbauer and IR spectroscopies, as well as TEM, X-ray photoelectron emission spectroscopy, and Brunauer-Emmett-Teller measurements, we suggest three scavenging mechanisms for the removal of metals including their incorporation into the ferrihydrite crystal structure, the formation of a separate phase, and their adsorption onto the precipitate surface. Zn and Cu are preferentially and almost completely incorporated into the crystal structure of the iron(III) oxyhydroxides; the formation of the Cd-bearing, X-ray amorphous phase, together with Cd carbonate is the principal mechanism of Cd removal. Interestingly, Ni remains predominantly in solution due to the key role of nickel(II) carbonate, which exhibits a solubility product constant several orders of magnitude higher than the carbonates of the other metals. Traces of Ni, identified in the iron(III) precipitate, are exclusively adsorbed onto the large surface area of nanoparticles. We discuss the relationship between the crystal structure of iron(III) oxyhydroxides and the mechanism of metal removal, as well as the linear relationship observed between the rate constant and the surface area of precipitates. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Ag-ligand modified tungstovandates and their efficient catalysis degradation properties for methylene blue

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zheng, Ran; Zhang, Huixia; Liu, Yunping

Two polytungstovandates [Ag(mbpy){sub 2}][Ag{sub 2}(mbpy){sub 3}][VW{sub 5}O{sub 19}]·H{sub 2}O (1) and [Ag(mbpy)]{sub 2}[Ag(mbpy){sub 2}]{sub 4}[VW{sub 12}O{sub 40}] (2) (mbpy =4,4′-dimethyl-2,2′-bipyridyl), had been hydrothermally synthesized and characterized by IR, TG, and single-crystal X-ray diffraction techniques. Single-crystal structural analysis revealed that the polyanionic clusters in two compounds are different: Lindqvist-type in 1 and α-Keggin-type in 2, respectively, while the cationic moieties in them are Ag-mbpy units. The experiments showed that this kind of hybrid crystal materials possesses more efficiently catalytic performance for the degradation of organic dye methylene blue (MB) in water solution under the UV irradiation. The significant degradation rate ofmore » MB can reach 89.9%, 94.9% by crystals 1 and 2 (40 mg) in the course of about 5 min. - Graphical abstract: Two Ag-ligand modified polytungstovandates had been synthesized and characterized, which were active in the catalytic degradation of organic dye methylene blue under the UV irradiation. - Highlights: • Two Ag-ligand modified tungstovandates were synthesized and characterized. • Weak interactions play important roles in constructing crystal frameworks. • Compounds are active to catalyze the degradation of methylene blue.« less

Achieving an Accurate Surface Profile of a Photonic Crystal for Near-Unity Solar Absorption in a Super Thin-Film Architecture.

PubMed

Kuang, Ping; Eyderman, Sergey; Hsieh, Mei-Li; Post, Anthony; John, Sajeev; Lin, Shawn-Yu

2016-06-28

In this work, a teepee-like photonic crystal (PC) structure on crystalline silicon (c-Si) is experimentally demonstrated, which fulfills two critical criteria in solar energy harvesting by (i) its Gaussian-type gradient-index profile for excellent antireflection and (ii) near-orthogonal energy flow and vortex-like field concentration via the parallel-to-interface refraction effect inside the structure for enhanced light trapping. For the PC structure on 500-μm-thick c-Si, the average reflection is only ∼0.7% for λ = 400-1000 nm. For the same structure on a much thinner c-Si ( t = 10 μm), the absorption is near unity (A ∼ 99%) for visible wavelengths, while the absorption in the weakly absorbing range (λ ∼ 1000 nm) is significantly increased to 79%, comparing to only 6% absorption for a 10-μm-thick planar c-Si. In addition, the average absorption (∼94.7%) of the PC structure on 10 μm c-Si for λ = 400-1000 nm is only ∼3.8% less than the average absorption (∼98.5%) of the PC structure on 500 μm c-Si, while the equivalent silicon solid content is reduced by 50 times. Furthermore, the angular dependence measurements show that the high absorption is sustained over a wide angle range (θinc = 0-60°) for teepee-like PC structure on both 500 and 10-μm-thick c-Si.

Crystal structure and infrared spectra of dicesium trans-tetraaquadichlorochromium(III) chloride

NASA Astrophysics Data System (ADS)

Neumann, E.; Stefov, V.; Šoptrajanov, B.; Engelen, B.; Lutz, H. D.

2004-12-01

The crystal structure of dicesium trans-tetraaquadichlorochromium(III) chloride Cs 2Cr IIICl 5·4H 2O with trans-[M IIIX 2(H 2O) 4] + complex ions (space group C2/c, Z=4, a=1915.3(4) pm, b=614.1(1) pm, c=1392.0(3) pm, and β=118.24(3)°, final R1=0.0246 for 2100 unique reflections) was redetermined by single-crystal X-ray diffraction studies. It was found to crystallize in a 2c super structure of the structure reported previously (Inorg. Chem. 20 (1981) 1566; Inorg. Chem. 36 (1997) 2248). The obtained structure data now agree with the results of infrared spectroscopic studies, which has been confirmed in this work, namely that there are two different hydrate H 2O molecules in the structure. Phase transitions, static or dynamic disorder of the hydrate H 2O molecules, and space group C2/m proposed in the literature were ruled out. The coordinates of the four hydrogen positions derived from the X-ray data have been improved via the O-H distances derived from the wave numbers of the OD stretching modes of matrix isolated HDO molecules (2426, 2323, and 2306 cm -1, 263 K) by using the νOD versus rO-H correlation curve reported in the literature (J. Mol. Struct. 404 (1997) 63). The νOD versus rH⋯Cl correlation curve reported by Mikenda (J. Mol. Struct. 147 (1986) 1) should be improved, especially for strong hydrogen bonds. The two hydrate H 2O molecules of the title compound are strongly distorted with a weak and a relatively strong O-H⋯Cl hydrogen bond each thus intramolecular coupling of the two OH stretching vibrations to coupled ones is largely reduced and, hence, the wavenumbers of the OH and OD stretching modes of the HDO molecules mainly resemble those of the H 2O and D 2O molecules. The strength of the hydrogen bonds is in accordance with the predictions of the competitive and synergetic effects. Chloro ligands are weaker hydrogen bond acceptor groups than chloride ions.

Crystal structure of di-methyl-formamidium bis-(tri-fluoro-methane-sulfon-yl)amide: an ionic liquid.

PubMed

Cardenas, Allan Jay P; O'Hagan, Molly

2016-09-01

At 100 K, the title mol-ecular salt, C 3 H 8 NO + ·C 2 F 6 NO 4 S 2 - , has ortho-rhom-bic ( P 2 1 2 1 2 1 ) symmetry; the amino H atom of bis-(tri-fluoro-methane-sulfon-yl)amine (HNTf 2 ) was transferred to the basic O atom of di-methyl-formamide (DMF) when the ionic liquid components were mixed. The structure displays an O-H⋯N hydrogen bond, which links the cation to the anion, which is reinforced by a non-conventional C-H⋯O inter-action, generating an R 2 2 (7) loop. A further very weak C-H⋯O inter-action generates an [001] chain.

Advanced High Brilliance X-Ray Source

NASA Technical Reports Server (NTRS)

Gibson, Walter M.

1998-01-01

The possibility to dramatically increase the efficiency of laboratory based protein structure measurements through the use of polycapillary X-ray optics was investigated. This project initiated April 1, 1993 and concluded December 31, 1996 (including a no cost extension from June 31, 1996). This is a final report of the project. The basis for the project is the ability to collect X-rays from divergent electron bombardment laboratory X-ray sources and redirect them into quasiparallel or convergent (focused) beams. For example, a 0.1 radian (approx. 6 deg) portion of a divergent beam collected by a polycapillary collimator and transformed into a quasiparallel beam of 3 millradian (0.2 deg) could give a gain of 6(exp 2)/0.2(exp 2) x T for the intensity of a diffracted beam from a crystal with a 0.2 deg diffraction width. T is the transmission efficiency of the polycapillary diffraction optic, and for T=0.5, the gain would be 36/0.04 x O.5=45. In practice, the effective collection angle will depend on the source spot size, the input focal length of the optic (usually limited by the source spot-to-window distance on the x-ray tube) and the size of the crystal relative to the output diameter of the optic. The transmission efficiency, T, depends on the characteristics (fractional open area, surface roughness, shape and channel diameter) of the polycapillary optic and is typically in the range 0.2-0.4. These effects could substantially reduce the expected efficiency gain. During the course of this study, the possibility to use a weakly focused beam (0.5 deg convergence) was suggested which could give an additional 10-20 X efficiency gain for small samples . Weakly focused beams from double focusing mirrors are frequently used for macromolecular crystallography studies. Furthermore the crystals are typically oscillated by as much as 2 deg during each X-ray exposure in order to increase the reciprocal space (number of crystal planes) sampled and use of a slightly convergent beam could, in principle, provide a similar sampling benefit without oscillation. Although more problematic, because of complications in analyzing the diffraction patterns, it was also suggested that even more extreme beam convergence might be used to give another order of magnitude intensity gain and even smaller focused spot size which could make it possible to study smaller protein crystals than can be studied using standard laboratory based X-ray diffraction systems. This project represents the first systematic investigation of these possibilities. As initially proposed, the contract included requirements for design, purchase, evaluation and delivery of three polycapillary lenses to the Laboratory for Structural Biology at MSFC and demonstration of such optics at MSFC for selected protein crystal diffraction applications.

2-Amino­pyrimidin-1-ium 4-methyl­benzene­sulfonate

PubMed Central

Tabatabaee, Masoumeh; Noozari, Najmeh

2011-01-01

In the crystal structure of the title compound, C4H6N3 +·C7H7O3S−, inter­molecular N—H⋯O hydrogen bonds link the cations and anions into chains along [100]. Additional stabilization is provided by weak C—H⋯O hydrogen bonds. An inter­molecular π–π stacking inter­action with a centroid–centroid distance of 3.6957 (7) Å is also observed. The H atoms of the methyl group were refined as disordered over two sets of sites with equal occupancies PMID:21754830

Superconductivity in ThPd2Ge2

NASA Astrophysics Data System (ADS)

Domieracki, Krzysztof; Wiśniewski, Piotr; Wochowski, Konrad; Romanova, Tetiana; Hackemer, Alicja; Gorzelniak, Roman; Pikul, Adam; Kaczorowski, Dariusz

2018-05-01

Our on-going search for unconventional superconductors among the ThTE2Ge2 phases (TE is a d-electron transition metal) revealed that ThPd2Ge2, which crystallizes with a body-centered tetragonal ThCr2Si2-type structure, exhibits superconductivity at low temperatures. In this paper, we report on the electrical transport and thermodynamic properties of a polycrystalline sample of this new superconductor, extended down to 50 mK. The experimental data indicates weakly-coupled type-II superconductivity with Tc = 0.63(2) K and μ0Hc2(0) = 32(2) mT.

6-Oxo-5-[(trifluoro­meth­yl)sulfon­yl]-1,2,4a,5,6,11b-hexa­hydro-1,3-dioxolo[4,5-j]phenanthridin-2-yl benzoate

PubMed Central

Wu, Chunli; Li, Pan; Shi, Xiufang; Pan, Xiaotao; Wu, Jizhou

2011-01-01

In the title compound, C22H16F3NO7S, the two benzene rings are almost perpendicular, the dihedral angle between their mean planes being 87.1 (1)°. The terminal O atom of the benzoate moiety is disordered over two positions with site occupancies of 0.244 (15) and 0.756 (15). The crystal structure is stablized by two types of weak inter­molecular C—H⋯O hydrogen bonds. PMID:21523058

Methyl 4-eth-oxy-2-methyl-2H-1,2-benzothia-zine-3-carboxyl-ate 1,1-dioxide.

PubMed

Zia-Ur-Rehman, Muhammad; Choudary, Jamil Anwar; Elsegood, Mark R J; Akbar, Noshin; Latif Siddiqui, Hamid

2008-07-16

In the crystal structure of the title compound, C(13)H(15)NO(5)S, the mol-ecules exhibit weak S=O⋯H-C and C=O⋯H-C inter-molecular inter-actions and arrange themselves into centrosymmetric dimers by means of π-π inter-actions (ring centroids are separated by 3.619 Å, while the closest C⋯C contacts are 3.514 Å). 1,2-Benzothia-zines of this kind have a range of biological activities and are used as medicines in the treatment of inflammation and rheumatoid arthritis.

Topological valley-chiral edge states of Lamb waves in elastic thin plates

NASA Astrophysics Data System (ADS)

Wang, Jian; Mei, Jun

2018-05-01

We investigate the nontrivial topology of the band structure of Lamb waves in a thin phononic crystal plate. When inversion symmetry is broken, a valley pseudospin degree of freedom is formed around K and K‧ valleys for the A0 Lamb mode, which is decoupled from the S0 and SH0 modes in the low-frequency regime. Chiral edge states are explicitly demonstrated, which are immune to defects and exhibit unidirectional transport behaviors when intervalley scattering is weak. The quantum valley Hall effect is thus simulated in a simple way in the context of Lamb waves.

2-(2-Thien­yl)-4,5-dihydro-1H-imidazole

PubMed Central

Kia, Reza; Fun, Hoong-Kun; Kargar, Hadi

2009-01-01

In title compound, C7H8N2S, the five-membered rings are twisted by a dihedral angle of 5.17 (10)°. Two inter­molecular N—H⋯N and C—H⋯N hydrogen bonds to the same acceptor N atom form seven-membered rings, producing R 2 1(7) ring motifs. These inter­actions link neighbouring mol­ecules into one-dimensional chains extended along the c axis. The crystal structure is further stabilized by weak inter­molecular C—H⋯π inter­actions. PMID:21581910

Computer Simulation of Energy Parameters and Magnetic Effects in Fe-Si-C Ternary Alloys

NASA Astrophysics Data System (ADS)

Ridnyi, Ya. M.; Mirzoev, A. A.; Mirzaev, D. A.

2018-06-01

The paper presents ab initio simulation with the WIEN2k software package of the equilibrium structure and properties of silicon and carbon atoms dissolved in iron with the body-centered cubic crystal system of the lattice. Silicon and carbon atoms manifest a repulsive interaction in the first two nearest neighbors, in the second neighbor the repulsion being stronger than in the first. In the third and next-nearest neighbors a very weak repulsive interaction occurs and tends to zero with increasing distance between atoms. Silicon and carbon dissolution reduces the magnetic moment of iron atoms.

Crystal structures of RIalpha subunit of cyclic adenosine 5'-monophosphate (cAMP)-dependent protein kinase complexed with (Rp)-adenosine 3',5'-cyclic monophosphothioate and (Sp)-adenosine 3',5'-cyclic monophosphothioate, the phosphothioate analogues of cAMP.

PubMed

Wu, Jian; Jones, John M; Nguyen-Huu, Xuong; Ten Eyck, Lynn F; Taylor, Susan S

2004-06-01

Cyclic adenosine 5'-monophosphate (cAMP) is an ancient signaling molecule, and in vertebrates, a primary target for cAMP is cAMP-dependent protein kinase (PKA). (R(p))-adenosine 3',5'-cyclic monophosphothioate ((R(p))-cAMPS) and its analogues are the only known competitive inhibitors and antagonists for cAMP activation of PKA, while (S(p))-adenosine 3',5'-cyclic monophosphothioate ((S(p))-cAMPS) functions as an agonist. The crystal structures of a Delta(1-91) deletion mutant of the RIalpha regulatory subunit of PKA bound to (R(p))-cAMPS and (S(p))-cAMPS were determined at 2.4 and 2.3 A resolution, respectively. While the structures are similar to each other and to the crystal structure of RIalpha bound to cAMP, differences in the dynamical properties of the protein when (R(p))-cAMPS is bound are apparent. The structures highlight the critical importance of the exocyclic oxygen's interaction with the invariant arginine in the phosphate binding cassette (PBC) and the importance of this interaction for the dynamical properties of the interactions that radiate out from the PBC. The conformations of the phosphate binding cassettes containing two invariant arginine residues (Arg209 on domain A, and Arg333 on domain B) are somewhat different due to the sulfur interacting with this arginine. Furthermore, the B-site ligand together with the entire domain B show significant differences in their overall dynamic properties in the crystal structure of Delta(1-91) RIalpha complexed with (R(p))-cAMPS phosphothioate analogue ((R(p))-RIalpha) compared to the cAMP- and (S(p))-cAMPS-bound type I and II regulatory subunits, based on the temperature factors. In all structures, two structural solvent molecules exist within the A-site ligand binding pocket; both mediate water-bridged interactions between the ligand and the protein. No structured waters are in the B-site pocket. Owing to the higher resolution data, the N-terminal segment (109-117) of the RIalpha subunit can also be traced. This strand forms an intermolecular antiparallel beta-sheet with the same strand in an adjacent molecule and implies that the RIalpha subunit can form a weak homodimer even in the absence of its dimerization domain.

Crystal structures of three 1-[4-(4-bromo-but-oxy)-phen-yl] chalcone derivatives: (E)-1-[4-(4-bromo-but-oxy)-phen-yl]-3-phenyl-prop-2-en-1-one, (E)-1-[4-(4-bromo-but-oxy)-phen-yl]-3-(4-meth-oxy-phen-yl)prop-2-en-1-one and (E)-1-[4-(4-bromo-but-oxy)-phen-yl]-3-(3,4-di-meth-oxy-phen-yl)prop-2-en-1-one.

PubMed

Maragatham, Gunasekaran; Selvarani, Sivasamy; Rajakumar, Perumal; Lakshmi, Srinivasakannan

2017-07-01

The crystal structures of three chalcones with a bromo-substituted but-oxy side chain, viz . ( E )-1-[4-(4-bromo-but-oxy)-phen-yl]-3-phenyl-prop-2-en-1-one, C 19 H 19 BrO 2 , (I), ( E )-1-[4-(4-bromo-but-oxy)-phen-yl]-3-(4-meth-oxy-phen-yl)prop-2-en-1-one, C 20 H 21 BrO 3 , (II), and ( E )-1-[4-(4-bromo-but-oxy)-phen-yl]-3-(3,4-di-meth-oxy-phen-yl)prop-2-en-1-one, C 21 H 23 BrO 4 , (III), are reported. In all mol-ecules, the conformation of the keto group with respect to the olefinic bond is s - cis . Mol-ecules of (I) and (II) are nearly planar, while mol-ecule (III) is not planar. In the crystal of compounds (I) and (II), mol-ecules are linked into chains parallel to the c axis by C-H⋯π inter-actions. In the crystal of compound (III), mol-ecules are linked by a pairs of C-H⋯O hydrogen bonds, forming inversion dimers. Weak C-Br⋯π inter-actions are also observed in (III).

Local structural ordering in surface-confined liquid crystals

NASA Astrophysics Data System (ADS)

Śliwa, I.; Jeżewski, W.; Zakharov, A. V.

2017-06-01

The effect of the interplay between attractive nonlocal surface interactions and attractive pair long-range intermolecular couplings on molecular structures of liquid crystals confined in thin cells with flat solid surfaces has been studied. Extending the McMillan mean field theory to include finite systems, it has been shown that confining surfaces can induce complex orientational and translational ordering of molecules. Typically, local smectic A, nematic, and isotropic phases have been shown to coexist in certain temperature ranges, provided that confining cells are sufficiently thick, albeit finite. Due to the nonlocality of surface interactions, the spatial arrangement of these local phases can display, in general, an unexpected complexity along the surface normal direction. In particular, molecules located in the vicinity of surfaces can still be organized in smectic layers, even though nematic and/or isotropic order can simultaneously appear in the interior of cells. The resulting surface freezing of smectic layers has been confirmed to occur even for rather weak surface interactions. The surface interactions cannot, however, prevent smectic layers from melting relatively close to system boundaries, even when molecules are still arranged in layers within the central region of the system. The internal interfaces, separating individual liquid-crystal phases, are demonstrated here to form fronts of local finite-size transitions that move across cells under temperature changes. Although the complex molecular ordering in surface confined liquid-crystal systems can essentially be controlled by temperature variations, specific thermal properties of these systems, especially the nature of the local transitions, are argued to be strongly conditioned to the degree of molecular packing.

Role of tool marks inside spherical mitigation pit fabricated by micro-milling on repairing quality of damaged KH2PO4 crystal

PubMed Central

Chen, Ming-Jun; Cheng, Jian; Yuan, Xiao-Dong; Liao, Wei; Wang, Hai-Jun; Wang, Jing-He; Xiao, Yong; Li, Ming-Quan

2015-01-01

Repairing initial slight damage site into stable structures by engineering techniques is the leading strategy to mitigate the damage growth on large-size components used in laser-driven fusion facilities. For KH2PO4 crystals, serving as frequency converter and optoelectronic switch-Pockels cell, micro-milling has been proven the most promising method to fabricate these stable structures. However, tool marks inside repairing pit would be unavoidably introduced due to the wearing of milling cutter in actual repairing process. Here we quantitatively investigate the effect of tool marks on repairing quality of damaged crystal components by simulating its induced light intensification and testing the laser-induced damage threshold. We found that due to the formation of focusing hot spots and interference ripples, the light intensity is strongly enhanced with the presence of tool marks, especially for those on rear surfaces. Besides, the negative effect of tool marks is mark density dependent and multiple tool marks would aggravate the light intensification. Laser damage tests verified the role of tool marks as weak points, reducing the repairing quality. This work offers new criterion to comprehensively evaluate the quality of repaired optical surfaces to alleviate the bottleneck issue of low laser damage threshold for optical components in laser-driven fusion facilities. PMID:26399624

Transition to collapsed tetragonal phase in CaFe2As2 single crystals as seen by 57Fe Mössbauer spectroscopy

NASA Astrophysics Data System (ADS)

Bud'ko, Sergey L.; Ma, Xiaoming; Tomić, Milan; Ran, Sheng; Valentí, Roser; Canfield, Paul C.

2016-01-01

Temperature dependent measurements of 57Fe Mössbauer spectra on CaFe2As2 single crystals in the tetragonal and collapsed tetragonal phases are reported. Clear features in the temperature dependencies of the isomer shift, relative spectra area, and quadrupole splitting are observed at the transition from the tetragonal to the collapsed tetragonal phase. From the temperature dependent isomer shift and spectral area data, an average stiffening of the phonon modes in the collapsed tetragonal phase is inferred. The quadrupole splitting increases by ˜25 % on cooling from room temperature to ˜100 K in the tetragonal phase and is only weakly temperature dependent at low temperatures in the collapsed tetragonal phase, in agreement with the anisotropic thermal expansion in this material. In order to gain microscopic insight about these measurements, we perform ab initio density functional theory calculations of the electric field gradient and the electron density of CaFe2As2 in both phases. By comparing the experimental data with the calculations we are able to fully characterize the crystal structure of the samples in the collapsed-tetragonal phase through determination of the As z coordinate. Based on the obtained temperature dependent structural data we are able to propose charge saturation of the Fe-As bond region as the mechanism behind the stabilization of the collapsed-tetragonal phase at ambient pressure.

Defects induced in cerium dioxide single crystals by electron irradiation

DOE PAGES

Costantini, Jean-Marc; Miro, Sandrine; Touati, Nadia; ...

2018-01-12

In this work, Micro-Raman spectroscopy, X-band electron paramagnetic resonance (EPR) spectroscopy, and UV-visible optical absorption spectroscopy were used to study the damage production in cerium dioxide (CeO 2) single crystals by electron irradiation for three energies (1.0, 1.4, and 2.5 MeV). The Raman-active T 2g peak was left unchanged after 2.5-MeV electron irradiation at a high fluence. This shows that no structural modifications occurred for the cubic fluorite structure. UV-visible optical absorption spectra exhibited a characteristic sub band-gap tail for 1.4-MeV and 2.5-MeV energies, but not for 1.0 MeV. Narrow EPR lines were recorded near liquid-helium temperature after 2.5-MeV electronmore » irradiation; whereas no such signal was found for the virgin un-irradiated crystal or after 1.0-MeV irradiation for the same fluence. The angular variation of these lines in the {111} plane revealed a weak g-factor anisotropy assigned to Ce 3+ ions (with the 4f 1 configuration) in a high-symmetry local environment. Finally, it is concluded that Ce 3+ ions may be produced by a reduction resulting from the displacement damage process. However, no evidence of F + or F 0 center or hole center formation due to irradiation was found from the present EPR and optical absorption spectra.« less

Defects induced in cerium dioxide single crystals by electron irradiation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Costantini, Jean-Marc; Miro, Sandrine; Touati, Nadia

In this work, Micro-Raman spectroscopy, X-band electron paramagnetic resonance (EPR) spectroscopy, and UV-visible optical absorption spectroscopy were used to study the damage production in cerium dioxide (CeO 2) single crystals by electron irradiation for three energies (1.0, 1.4, and 2.5 MeV). The Raman-active T 2g peak was left unchanged after 2.5-MeV electron irradiation at a high fluence. This shows that no structural modifications occurred for the cubic fluorite structure. UV-visible optical absorption spectra exhibited a characteristic sub band-gap tail for 1.4-MeV and 2.5-MeV energies, but not for 1.0 MeV. Narrow EPR lines were recorded near liquid-helium temperature after 2.5-MeV electronmore » irradiation; whereas no such signal was found for the virgin un-irradiated crystal or after 1.0-MeV irradiation for the same fluence. The angular variation of these lines in the {111} plane revealed a weak g-factor anisotropy assigned to Ce 3+ ions (with the 4f 1 configuration) in a high-symmetry local environment. Finally, it is concluded that Ce 3+ ions may be produced by a reduction resulting from the displacement damage process. However, no evidence of F + or F 0 center or hole center formation due to irradiation was found from the present EPR and optical absorption spectra.« less

Reduced Iron Sulfide Systems for Removal of Heavy Metal Ions from Groundwater

DTIC Science & Technology

2009-07-01

be gleaned from higher magnification of these samples. Each set of lattice fringes represents a single crystal of mackinawite (Ohfuji and Ricard...diffractograms, the diffraction peaks are broad and weak, indicating a poor degree of crystallization or a small crystallite size. For the non-magnetic...the lattice spacings of synthetic mackinawite in this study are shorter. The 3-day aging in this study resulted in a higher degree of crystallization

Mechanisms for the Crystallization of ZBLAN

NASA Technical Reports Server (NTRS)

Ethridge, Edwin C.; Tucker, Dennis S.; Kaukler, William; Antar, Basil

2003-01-01

The objective of this ground based study is to test the hypothesis that shear thinning (the non-Newtonian response of viscosity to shear rate) is a viable mechanism to explain the observation of enhanced glass formation in numerous low-g experiments. In 1-g, fluid motion results from buoyancy forces and surface tension driven convection. This fluid flow will introduce shear in undercooled liquids in 1-g. In low-g it is known that fluid flows are greatly reduced so that the shear rate in fluids can be extremely low. It is believed that some fluids may have weak structure in the absence of flow. Very small shear rates could cause this structure to collapse in response to shear resulting in a lowering of the viscosity of the fluid. The hypothesis of this research is that: Shear thinning in undercooled liquids decreases the viscosity, increasing the rate of nucleation and crystallization of glass forming melts. Shear in the melt can be reduced in low-g, thus enhancing undercooling and glass formation. The viscosity of a model glass (lithium di-silicate, L2S) often used for crystallization studies has been measured at very low shear rates using a dynamic mechanical thermal analyzer. Our results are consistent with increasing viscosity with a lowering of shear rates. The viscosity of L2S may vary as much as an order of magnitude depending on the shear rate in the temperature region of maximum nucleation and crystal growth. Classical equations for nucleation and crystal growth rates, are inversely related to the viscosity and viscosity to the third power respectively. An order of magnitude variation in viscosity (with shear) at a given temperature would have dramatic effects on glass crystallization Crystallization studies with the heavy metal fluoride glass ZBLAN (ZrF2-BaF2-LaF3-AlF3-NaF) to examine the effect of shear on crystallization are being initiated. Samples are to be melted and quenched under quiescent conditions at different shear rates to determine the effect on crystallization. The results from this study are expected to advance the current scientific understanding of glass formation in low-g and glass crystallization under glass molding conditions and will improve the scientific understanding of technological processes such as fiber pulling, bulk amorphous alloys, and glass fabrication processes.

The effect of an electric field on the morphological stability of the crystal-melt interface of a binary alloy. III - Weakly nonlinear theory

NASA Technical Reports Server (NTRS)

Wheeler, A. A.; Mcfadden, G. B.; Coriell, S. R.; Hurle, D. T. J.

1990-01-01

The effect of a constant electric current on the crystal-melt interface morphology during directional solidification at constant velocity of a binary alloy is considered. A linear temperature field is assumed, and thermoelectric effects and Joule heating are neglected; electromigration and differing electrical conductivities of crystal and melt are taken into account. A two-dimensional weakly nonlinear analysis is carried out to third order in the interface amplitude, resulting in a cubic amplitude equation that describes whether the bifurcation from the planar state is supercritical or subcritical. For wavelengths corresponding to the most dangerous mode of linear theory, the demarcation between supercritical and subcritical behavior is calculated as a function of processing conditions and material parameters. The bifurcation behavior is a sensitive function of the magnitude and direction of the electric current and of the electrical conductivity ratio.

New insights into the application of the valence rules in Zintl phases—Crystal and electronic structures of Ba{sub 7}Ga{sub 4}P{sub 9}, Ba{sub 7}Ga{sub 4}As{sub 9}, Ba{sub 7}Al{sub 4}Sb{sub 9}, Ba{sub 6}CaAl{sub 4}Sb{sub 9}, and Ba{sub 6}CaGa{sub 4}Sb{sub 9}

DOE Office of Scientific and Technical Information (OSTI.GOV)

He, Hua; Stoyko, Stanislav; Bobev, Svilen, E-mail: bobev@udel.edu

Crystals of three new ternary pnictides—Ba{sub 7}Al{sub 4}Sb{sub 9}, Ba{sub 7}Ga{sub 4}P{sub 9}, and Ba{sub 7}Ga{sub 4}As{sub 9} have been prepared by reactions of the respective elements in molten Al or Pb fluxes. Single-crystal X-ray diffraction studies reveal that the three phases are isotypic, crystallizing in the orthorhombic Ba{sub 7}Ga{sub 4}Sb{sub 9}-type structure (space group Pmmn, Pearson symbol oP40, Z=2), for which only the prototype is known. The structure is based on TrPn{sub 4} tetrahedra (Tr=Al, Ga; Pn=P, As, Sb), connected in an intricate scheme into 1D-ribbons. Long interchain Pn–Pn bonds (d{sub P–P}>3.0 Å; d{sub As–As}>3.1 Å; d{sub Sb–Sb}>3.3 Å)more » account for the realization of 2D-layers, separated by Ba{sup 2+} cations. Applying the classic valance rules to rationalize the bonding apparently fails, and Ba{sub 7}Ga{sub 4}Sb{sub 9} has long been known as a metallic Zintl phase. Earlier theoretical calculations, both empirical and ab-initio, suggest that the possible metallic properties originate from filled anti-bonding Pn–Pn states, and the special roles of the “cations” in this crystal structure. To experimentally probe this hypothesis, we sought to synthesize the ordered quaternary phases Ba{sub 6}CaTr{sub 4}Sb{sub 9} (Tr=Al, Ga). Single-crystal X-ray diffraction work confirms Ba{sub 6.145(3)}Ca{sub 0.855}Al{sub 4}Sb{sub 9} and Ba{sub 6.235(3)}Ca{sub 0.765}Ga{sub 4}Sb{sub 9}, with Ca atoms preferably substituting Ba on one of the three available sites. The nuances of the five crystal structures are discussed, and the chemical bonding in Ba{sub 7}Ga{sub 4}As{sub 9} is interrogated by tight-binding linear muffin-tin orbital calculations. - Graphical abstract: The new Zintl phases—Ba{sub 7}Al{sub 4}Sb{sub 9}, Ba{sub 7}Ga{sub 4}P{sub 9}, and Ba{sub 7}Ga{sub 4}As{sub 9}, and their quaternary variants Ba{sub 6}CaTr{sub 4}Sb{sub 9} (Tr=Al, Ga)—crystallize in the Ba{sub 7}Ga{sub 4}Sb{sub 9} structure type. The structures are based on TrPn{sub 4} tetrahedra (a perspective of the crystal structure is shown, as viewed along the c axis). - Highlights: • Ba{sub 7}Al{sub 4}Sb{sub 9}, Ba{sub 7}Ga{sub 4}P{sub 9}, and Ba{sub 7}Ga{sub 4}As{sub 9} are new compounds in the respective phase diagrams. • The quaternary phases Ba{sub 6}CaTr{sub 4}Sb{sub 9} (Tr=Al, Ga) show nearly ordered Ba/Ca distribution. • Very weak Pn–Pn bonds and pairing distortion are observed for Ba{sub 7}Ga{sub 4}Pn{sub 9} (Pn=P, As).« less

The active site of hen egg-white lysozyme: flexibility and chemical bonding

DOE Office of Scientific and Technical Information (OSTI.GOV)

Held, Jeanette, E-mail: jeanette.netzel@uni-bayreuth.de; Smaalen, Sander van

Chemical bonding at the active site of lysozyme is analyzed on the basis of a multipole model employing transferable multipole parameters from a database. Large B factors at low temperatures reflect frozen-in disorder, but therefore prevent a meaningful free refinement of multipole parameters. Chemical bonding at the active site of hen egg-white lysozyme (HEWL) is analyzed on the basis of Bader’s quantum theory of atoms in molecules [QTAIM; Bader (1994 ▶), Atoms in Molecules: A Quantum Theory. Oxford University Press] applied to electron-density maps derived from a multipole model. The observation is made that the atomic displacement parameters (ADPs) ofmore » HEWL at a temperature of 100 K are larger than ADPs in crystals of small biological molecules at 298 K. This feature shows that the ADPs in the cold crystals of HEWL reflect frozen-in disorder rather than thermal vibrations of the atoms. Directly generalizing the results of multipole studies on small-molecule crystals, the important consequence for electron-density analysis of protein crystals is that multipole parameters cannot be independently varied in a meaningful way in structure refinements. Instead, a multipole model for HEWL has been developed by refinement of atomic coordinates and ADPs against the X-ray diffraction data of Wang and coworkers [Wang et al. (2007), Acta Cryst. D63, 1254–1268], while multipole parameters were fixed to the values for transferable multipole parameters from the ELMAM2 database [Domagala et al. (2012), Acta Cryst. A68, 337–351] . Static and dynamic electron densities based on this multipole model are presented. Analysis of their topological properties according to the QTAIM shows that the covalent bonds possess similar properties to the covalent bonds of small molecules. Hydrogen bonds of intermediate strength are identified for the Glu35 and Asp52 residues, which are considered to be essential parts of the active site of HEWL. Furthermore, a series of weak C—H⋯O hydrogen bonds are identified by means of the existence of bond critical points (BCPs) in the multipole electron density. It is proposed that these weak interactions might be important for defining the tertiary structure and activity of HEWL. The deprotonated state of Glu35 prevents a distinction between the Phillips and Koshland mechanisms.« less

Morphological diversity of nitroguanidine crystals with enhanced mechanical performance and thermodynamic stability

NASA Astrophysics Data System (ADS)

Luo, Zhilong; Cui, Yingdan; Dong, Weibing; Xu, Qipeng; Zou, Gaoxing; Kang, Chao; Hou, Baohong; Chen, Song; Gong, Junbo

2017-12-01

Nitroguanidine (NQ) is a commonly used explosive, which has been widely used for both civilian and military explosive applications. However, the weak flowability and mechanical performance limit its application. In this work, mechanical performance and thermodynamic stability of NQ crystals were improved by controlling crystal morphologies in the crystallization process. Typical NQ crystals with multiple morphologies and single crystal form were obtained in the presence of additives during the cooling crystallization. The morphology controlled NQ crystals showed higher density, unimodal crystal size distribution and enhanced flowability. The additives showed the inhibitory effect on the nucleation of NQ crystals by in-situ FBRM and PVM determination, and the mechanism was analyzed by means of morphological prediction and molecular simulation. Furthermore, the morphology controlled NQ crystals suggested higher thermodynamic stability according to the calculation of entropy, enthalpy, Gibbs free energy and apparent activation energy on the basis of DSC results.

[Synthesis and characterization of CO-3(2-) doping nano-hydroxyapatite].

PubMed

Liao, Jian-Guo; Li, Yan-Qun; Duan, Xing-Ze; Liu, Qiong

2014-11-01

CO3(2-) doping is an effective method to increase the biological activity of nano-hydroxyapatite (n-HA). In the present study, calcium nitrate and trisodium phosphate were chosen as raw materials, with a certain amount of Na2CO3 as a source of CO-3(2-) ions, to synthesize nano-carbonate hydroxyapatite (n-CHA) slurry by solution precipitation method. The structure and micro-morphology of n-CHA were characterized by transmission electron microscope (TEM), X-ray diffraction (XRD), Fourier transform-infrared spectroscopy (FTIR) and Raman spectroscopy (RS). The results revealed that the synthetic n-HA crystals are acicular in nanometer scale and have a crystal size of 20-30 nm in diameter and 60-80 nm in length, which are similar to natural bone apatite. And the crystallinity of n-CHA crystals decreases to the increment of CO3(2-). Samples with more CO3(2) have composition and structure more similar to the bone apatite. The value of lattice parameters a decreases, value of c increases, and c/a value increases with the increase in the amount of CO3(2-), in accordance with crystal cell parameters change rule of type B replacement. In the AB mixed type (substitution OH- and PO4(3-)) CHA, IR characteristic peak of CO3(2-) out-of-plane bending vibration appears at 872 cm(-1), meanwhile, the asymmetry flexible vibration band is split into band at 1 454 cm(-1) and band at 1 420 cm(-1), while weak CO3(2)-peak appears at 1 540 cm(-1). CO3(2-) Raman peak of symmetric stretching vibration appears at 1 122 cm(-1). CO3(2-) B-type (substitution PO4(3-)) peak appeared at 1 071 cm(-1). Through the calculation of integral area ratio of PO4(3-)/ CO3(2-), OH-/CO3(2-), and PO4(3-)/OH-, low quantity CO3(2-) is B-type and high quantity CO3(2-) is A-type (substitution OH-). The results show that the synthesized apatite crystals are AB hybrid substitued nano-carbonate hydroxyapatite, however B-type replacement is the main substitute mode. Due to similarity inthe shape, size, crystal structure and growth mode, the synthesized apatite crystals can be called a kind of bone-like apatite.

New 7-arylpiperazinylalkyl-8-morpholin-4-yl-purine-2,6-dione derivatives with anxiolytic activity - Synthesis, crystal structure and structure-activity study

NASA Astrophysics Data System (ADS)

Chłoń-Rzepa, Grażyna; Żmudzki, Paweł; Pawłowski, Maciej; Wesołowska, Anna; Satała, Grzegorz; Bojarski, Andrzej J.; Jabłoński, Mateusz; Kalinowska-Tłuścik, Justyna

2014-06-01

On the basis of our earlier studies with serotonin (5-HT) receptor ligands in the group of long-chain arylpiperazines (LCAPs), a new series of 7-arylpiperazinylalkyl-8-morpholin-4-yl-purine-2,6-dione derivatives (5-12) has been designed, synthesised and studied in vitro for their affinity for 5-HT1A, 5-HT2A, 5-HT6 and 5-HT7 receptors. The introduction of o-OCH3 and m-Cl into the phenylpiperazinyl moiety as well as the elongation of the linker between purine-2,6-dione core and arylpiperazine fragment modified the affinity for the tested 5-HT receptors. The structures of compounds 9-11 (hydrochloride salts) were confirmed by an X-ray diffraction method. All molecules adopted a different conformation in the crystal. The strongest observed type of interaction is a charge assisted hydrogen bond N+-H⋯Cl-. Additionally, the π-π interactions between 1,3-dimethyl-3,7-dihydropurine-2,6-dione cores of the neighbouring molecules were also observed. As it is observed in the presented crystal structures, the morpholine ring (a potential donor and acceptor of the hydrogen bonds) seems to be an attractive substituent, that may support binding to the non-specific sites of 5-HT receptors. Another interesting feature is the mutual orientation of rings in the arylpiperazine fragment, with plausible influence on ligand-receptor recognition. For compound 10, with strong 5-HT1A binding affinity, the mutual orientation of rings is determined by the intramolecular weak C-H⋯O hydrogen bond. This observation may contribute to a better understanding of the more selective binding of o-OCH3 arylpiperazine derivatives to the 5-HT1A receptor.

Crystal Structure of Crataeva tapia Bark Protein (CrataBL) and Its Effect in Human Prostate Cancer Cell Lines

PubMed Central

Ferreira, Joana Gasperazzo; Silva, Mariana Cristina Cabral; Silva-Lucca, Rosemeire Aparecida; Mentele, Reinhard; Paredes-Gamero, Edgar Julian; Bertolin, Thiago Carlos; dos Santos Correia, Maria Tereza; Paiva, Patrícia Maria Guedes; Gustchina, Alla; Wlodawer, Alexander; Oliva, Maria Luiza Vilela

2013-01-01

A protein isolated from the bark of Crataeva tapia (CrataBL) is both a Kunitz-type plant protease inhibitor and a lectin. We have determined the amino acid sequence and three-dimensional structure of CrataBL, as well as characterized its selected biochemical and biological properties. We found two different isoforms of CrataBL isolated from the original source, differing in positions 31 (Pro/Leu); 92 (Ser/Leu); 93 (Ile/Thr); 95 (Arg/Gly) and 97 (Leu/Ser). CrataBL showed relatively weak inhibitory activity against trypsin (Kiapp = 43 µM) and was more potent against Factor Xa (Kiapp = 8.6 µM), but was not active against a number of other proteases. We have confirmed that CrataBL contains two glycosylation sites and forms a dimer at high concentration. The high-resolution crystal structures of two different crystal forms of isoform II verified the β-trefoil fold of CrataBL and have shown the presence of dimers consisting of two almost identical molecules making extensive contacts (∼645 Å2). The structure differs from those of the most closely related proteins by the lack of the N-terminal β-hairpin. In experiments aimed at investigating the biological properties of CrataBL, we have shown that addition of 40 µM of the protein for 48 h caused maximum growth inhibition in MTT assay (47% of DU145 cells and 43% of PC3 cells). The apoptosis of DU145 and PC3 cell lines was confirmed by flow cytometry using Annexin V/FITC and propidium iodide staining. Treatment with CrataBL resulted in the release of mitochondrial cytochrome c and in the activation of caspase-3 in DU145 and PC3 cells. PMID:23823708

[Pb2F2](SeO4): a heavier analogue of grandreefite, the first layered fluoride selenate

NASA Astrophysics Data System (ADS)

Charkin, Dmitri O.; Plokhikh, Igor V.; Zadoya, Anastasiya I.; Kazakov, Sergey M.; Zaloga, Alexander N.; Kozin, Michael S.; Depmeier, Wulf; Siidra, Oleg I.

2018-01-01

Co-precipitation of PbF2 and PbSeO4 in weakly acidic media results in the formation of [Pb2F2](SeO4), the selenate analogue of the naturally occurring mineral grandreefite, [Pb2F2](SO4). The new compound is monoclinic, C2/ c, a = 14.0784(2) Å, b = 4.6267(1) Å, c = 8.8628(1) Å, β = 108.98(1)°, V = 545.93(1) Å3. Its structure has been refined from powder data to R B = 1.55%. From thermal studies, it is established that the compound is stable in air up to about 300 °C, after which it gradually converts into a single phase with composition [Pb2O](SeO4), space group C2/ m, and lattice parameters a = 14.0332(1) Å, b = 5.7532(1) Å, c = 7.2113(1) Å, β = 115.07(1)°, V = 527.37(1) Å3. It is the selenate analogue of lanarkite, [Pb2O](SO4), and phoenicochroite, [Pb2O](CrO4), and its crystal structure was refined to R B = 1.21%. The formation of a single decomposition product upon heating in air suggests that this happens by a thermal hydrolysis mechanism, i.e., Pb2F2SeO4 + H2O (vapor) → Pb2OSeO4 + 2HF↑. This relatively low-temperature process involves complete rearrangement of the crystal structure—from a 2D architecture featuring slabs [Pb2F2]2+ formed by fluorine-centered tetrahedra into a structure characterized by 1D motifs based on [OPb2]2+ chains of oxocentered tetrahedra. The comparative crystal chemistry of the obtained anion-centered structural architectures is discussed.

Syntheses, crystal structures, and properties of four coordination polymers based on mixed multi-N donor and polycarboxylate ligands

NASA Astrophysics Data System (ADS)

Chen, Shui-Sheng; Guo, Xing-Zhe; Zhao, Yue; Li, Wei-Dong

2018-02-01

Four new coordination polymers [Ni2(HL1)2(L1)3(BTC)2]·6H2O (1), [Ni2(L1)3(HBTC)2]·4H2O (2), [Cd2(L2)(BTC)(H2O)3]·2H2O (3) and [Cd2(HL2)(BTCA)] (4) were synthesized by reactions of nickel(II)/ cadmium(II) salts with rigid ligands of 1,4-di(1H-imidazol-4-yl)benzene (L1), 1,3-di(1-imidazolyl)-5-(4H-tetrazol-5-yl)benzene (HL2) and polycarboxylic acids of 1,3,5-benzenetricarboxylic acid (H3BTC), 1,2,4,5-benzenetetracarboxylic acid (H4BTCA), respectively. The structures of the complexes were determined by single crystal X-ray diffraction analysis. The complex 1 is one-dimensional (1D) chain while 2 is a (4, 4)-connected two-dimensional (2D) layered structure with 2D → 2D parallel interpenetration. Complex 3 is a rare tetranodal (3,4)-connected three-dimensional (3D) CrVTiSc architecture with Point (Schläfli) symbol of (4·82)(4·84·10)(42·82·102)(83), and compound 4 has the 2D network with (4,4) topology based on the [Cd2(COO)4] SBUs. The weak interactions such as hydrogen bonds and π···π stacking contribute to stabilize crystal structure and extend the low-dimensional entities into high-dimensional frameworks. The UV-vis absorption spectra of 1 - 4 are discussed. Moreover, the photo luminescent properties of 3 and 4 and gas sorption property of 2 have been investigated.

Biospecific protein immobilization for rapid analysis of weak protein interactions using self-interaction nanoparticle spectroscopy.

PubMed

Bengali, Aditya N; Tessier, Peter M

2009-10-01

"Reversible" protein interactions govern diverse biological behavior ranging from intracellular transport and toxic protein aggregation to protein crystallization and inactivation of protein therapeutics. Much less is known about weak protein interactions than their stronger counterparts since they are difficult to characterize, especially in a parallel format (in contrast to a sequential format) necessary for high-throughput screening. We have recently introduced a highly efficient approach of characterizing protein self-association, namely self-interaction nanoparticle spectroscopy (SINS; Tessier et al., 2008; J Am Chem Soc 130:3106-3112). This approach exploits the separation-dependent optical properties of gold nanoparticles to detect weak self-interactions between proteins immobilized on nanoparticles. A limitation of our previous work is that differences in the sequence and structure of proteins can lead to significant differences in their affinity to adsorb to nanoparticle surfaces, which complicates analysis of the corresponding protein self-association behavior. In this work we demonstrate a highly specific approach for coating nanoparticles with proteins using biotin-avidin interactions to generate protein-nanoparticle conjugates that report protein self-interactions through changes in their optical properties. Using lysozyme as a model protein that is refractory to characterization by conventional SINS, we demonstrate that surface Plasmon wavelengths for gold-avidin-lysozyme conjugates over a range of solution conditions (i.e., pH and ionic strength) are well correlated with lysozyme osmotic second virial coefficient measurements. Since SINS requires orders of magnitude less protein and time than conventional methods (e.g., static light scattering), we envision this approach will find application in large screens of protein self-association aimed at either preventing (e.g., protein aggregation) or promoting (e.g., protein crystallization) these interactions. (c) 2009 Wiley Periodicals, Inc.

Crystal structure of (4-cyano­pyridine-κN){5,10,15,20-tetrakis[4-(benzoyloxy)phenyl]porphyrinato-κ4 N}zinc–4-cyano­pyridine (1/1)

PubMed Central

Nasri, Soumaya; Amiri, Nesrine; Turowska-Tyrk, Ilona; Daran, Jean-Claude; Nasri, Habib

2016-01-01

In the title compound, [Zn(C72H44N4O8)(C6H4N2)]·C6H4N2 or [Zn(TPBP)(4-CNpy]·(4-CNpy) [where TPBP and 4-CNpy are 5,10,15,20-(tetra­phenyl­benzoate)porphyrinate and 4-cyano­pyridine, respectively], the ZnII cation is chelated by four pyrrole-N atoms of the porphyrinate anion and coordinated by a pyridyl-N atom of the 4-CNpy axial ligand in a distorted square-pyramidal geometry. The average Zn—N(pyrrole) bond length is 2.060 (6) Å and the Zn—N(4-CNpy) bond length is 2.159 (2) Å. The zinc cation is displaced by 0.319 (1) Å from the N4C20 mean plane of the porphyrinate anion toward the 4-cyano­pyridine axial ligand. This porphyrinate macrocycle exhibits major saddle and moderate ruffling and doming deformations. In the crystal, the [Zn(TPBP)(4-CNpy)] complex mol­ecules are linked together via weak C—H⋯N, C—H⋯O and C—H⋯π inter­actions, forming supra­molecular channels parallel to the c axis. The non-coordinating 4-cyano­pyridine mol­ecules are located in the channels and linked with the complex mol­ecules, via weak C—H⋯N inter­actions and π-π stacking or via weak C—H⋯O and C—H⋯π inter­actions. The non-coordinating 4-cyano­pyridine mol­ecule is disordered over two positions with an occupancy ratio of 0.666 (4):0.334 (4). PMID:26958379

X-ray and neutron diffraction study of the defect crystal structure of the as-grown nonstoichiometric phase Y{sub 0.715}Ca{sub 0.285}F{sub 2.715}

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bolotina, N. B., E-mail: bolotina@ns.crys.ras.ru; Kalyukanov, A. I.; Chernaya, T. S.

This work begins a series of papers aimed at studying the defect structure of nonstoichiometric phases R{sub 1-y}Ca{sub y}F{sub 3-y} with a tysonite-type (LaF{sub 3}) structure. In the single-crystal structure of Y{sub 0.715}Ca{sub 0.285}F{sub 2.715} with a tysonite-type small unit cell (sp. gr. P6{sub 3}/mmc, a = 3.9095(2) A, c = 6.9829(2) A; Z = 2; R{sub w} = 2.16%), the displacements of Y{sup 3+} cations and F{sup 2-} anions from 6{sub 3} symmetry axes were observed for the first time. The X-ray diffraction pattern shows weak satellites insufficient for structural calculations. The LaF{sub 3} structure type is stabilized upmore » and down on the temperature scale due to anion vacancies and the symmetrizing effect of Ca{sup 2+} cations lying on 6{sub 3} symmetry axes. At 120 Degree-Sign C the fluoride-ion conductivity in the nonstoichiometric phase Y{sub 0.715}Ca{sub 0.285}F{sub 2.715} is five orders of magnitude higher than that in the stoichiometric phase {beta}-YF{sub 3}. The transition to a superionic state is caused by a deviation from stoichiometry and is not associated with reconstructive phase transformation.« less

Electron-hole diffusion lengths >175 μm in solution-grown CH 3NH 3PbI 3 single crystals

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dong, Qingfeng; Fang, Yanjun; Shao, Yuchuan

Long, balanced electron and hole diffusion lengths greater than 100 nanometers in the polycrystalline organolead trihalide compound CH 3NH 3PbI 3 are critical for highly efficient perovskite solar cells. We found that the diffusion lengths in CH 3NH 3PbI 3 single crystals grown by a solution-growth method can exceed 175 micrometers under 1 sun (100 mW cm –2) illumination and exceed 3 millimeters under weak light for both electrons and holes. The internal quantum efficiencies approach 100% in 3-millimeter-thick single-crystal perovskite solar cells under weak light. These long diffusion lengths result from greater carrier mobility, longer lifetime, and much smallermore » trap densities in the single crystals than in polycrystalline thin films. As a result, the long carrier diffusion lengths enabled the use of CH 3NH 3PbI 3 in radiation sensing and energy harvesting through the gammavoltaic effect, with an efficiency of 3.9% measured with an intense cesium-137 source.« less

Dislocation dynamics and crystal plasticity in the phase-field crystal model

NASA Astrophysics Data System (ADS)

Skaugen, Audun; Angheluta, Luiza; Viñals, Jorge

2018-02-01

A phase-field model of a crystalline material is introduced to develop the necessary theoretical framework to study plastic flow due to dislocation motion. We first obtain the elastic stress from the phase-field crystal free energy under weak distortion and show that it obeys the stress-strain relation of linear elasticity. We focus next on dislocations in a two-dimensional hexagonal lattice. They are composite topological defects in the weakly nonlinear amplitude equation expansion of the phase field, with topological charges given by the standard Burgers vector. This allows us to introduce a formal relation between the dislocation velocity and the evolution of the slowly varying amplitudes of the phase field. Standard dissipative dynamics of the phase-field crystal model is shown to determine the velocity of the dislocations. When the amplitude expansion is valid and under additional simplifications, we find that the dislocation velocity is determined by the Peach-Koehler force. As an application, we compute the defect velocity for a dislocation dipole in two setups, pure glide and pure climb, and compare it with the analytical predictions.

Electron-hole diffusion lengths >175 μm in solution-grown CH 3NH 3PbI 3 single crystals

DOE PAGES

Dong, Qingfeng; Fang, Yanjun; Shao, Yuchuan; ...

2015-02-27

Long, balanced electron and hole diffusion lengths greater than 100 nanometers in the polycrystalline organolead trihalide compound CH 3NH 3PbI 3 are critical for highly efficient perovskite solar cells. We found that the diffusion lengths in CH 3NH 3PbI 3 single crystals grown by a solution-growth method can exceed 175 micrometers under 1 sun (100 mW cm –2) illumination and exceed 3 millimeters under weak light for both electrons and holes. The internal quantum efficiencies approach 100% in 3-millimeter-thick single-crystal perovskite solar cells under weak light. These long diffusion lengths result from greater carrier mobility, longer lifetime, and much smallermore » trap densities in the single crystals than in polycrystalline thin films. As a result, the long carrier diffusion lengths enabled the use of CH 3NH 3PbI 3 in radiation sensing and energy harvesting through the gammavoltaic effect, with an efficiency of 3.9% measured with an intense cesium-137 source.« less

Survival condition for low-frequency quasi-one-dimensional breathers in a two-dimensional strongly anisotropic crystal

NASA Astrophysics Data System (ADS)

Savin, A. V.; Zubova, E. A.; Manevitch, L. I.

2005-06-01

We investigate a two-dimensional (2D) strongly anisotropic crystal (2D SAC) on substrate: 2D system of coupled linear chains of particles with strong intrachain and weak interchain interactions, each chain being subjected to the sine background potential. Nonlinear dynamics of one of these chains when the rest of them are fixed is reduced to the well known Frenkel-Kontorova (FK) model. Depending on strengh of the substrate, the 2D SAC models a variety of physical systems: polymer crystals with identical chains having light side groups, an array of inductively coupled long Josephson junctions, anisotropic crystals having light and heavy sublattices. Continuum limit of the FK model, the sine-Gordon (sG) equation, allows two types of soliton solutions: topological solitons and breathers. It is known that the quasi-one-dimensional topological solitons can propagate also in a chain of 2D system of coupled chains and even in a helix chain in a three-dimensional model of polymer crystal. In contrast to this, numerical simulation shows that the long-living breathers inherent to the FK model do not exist in the 2D SAC with weak background potential. The effect changes scenario of kink-antikink collision with small relative velocity: at weak background potential the collision always results only in intensive phonon radiation while kink-antikink recombination in the FK model results in long-living low-frequency sG breather creation. We found the survival condition for breathers in the 2D SAC on substrate depending on breather frequency and strength of the background potential. The survival condition bears no relation to resonances between breather frequency and frequencies of phonon band—contrary to the case of the FK model.

Hybrid micro-/nano-structures derived from metal-organic frameworks: preparation and applications in energy storage and conversion.

PubMed

Cao, Xiehong; Tan, Chaoliang; Sindoro, Melinda; Zhang, Hua

2017-05-22

Metal-organic frameworks (MOFs), an important class of inorganic-organic hybrid crystals with intrinsic porous structures, can be used as versatile precursors or sacrificial templates for preparation of numerous functional nanomaterials for various applications. Recent developments of MOF-derived hybrid micro-/nano-structures, constructed by more than two components with varied functionalities, have revealed their extensive capabilities to overcome the weaknesses of the individual counterparts and thus give enhanced performance for energy storage and conversion. In this tutorial review, we summarize the recent advances in MOF-derived hybrid micro-/nano-structures. The synthetic strategies for preparing MOF-derived hybrid micro-/nano-structures are first introduced. Focusing on energy storage and conversion, we then discuss their potential applications in lithium-ion batteries, lithium-sulfur batteries, supercapacitors, lithium-oxygen batteries and fuel cells. Finally, we give our personal insights into the challenges and opportunities for the future research of MOF-derived hybrid micro-/nano-structures.

Effect of alkali cations on two-dimensional networks of two new quaternary thioarsenates (III) prepared by a facile surfactant-thermal method

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yan, Dongming; Hou, Peipei; Liu, Chang

2016-09-15

Two new quaternary thioarsenates(III) NaAg{sub 2}AsS{sub 3}·H{sub 2}O (1) and KAg{sub 2}AsS{sub 3} (2) with high yields have been successfully prepared through a facile surfactant-thermal method. It is interesting that 2 can only be obtained with the aid of ethanediamine (en), which indicates that weak basicity of solvent is beneficial to the growth of 2 compared with 1. Both 1 and 2 feature the similar two-dimensional (2D) layer structures. However, the distortion of the primary honeycomb-like nets in 2 is more severe than that of 1, which demonstrates that Na{sup +} and K{sup +} cations have different structure directing effectsmore » on these two thioarsenates(III). Both experimental and theoretical studies confirm 1 and 2 are semiconductors with band gaps in the visible region. Our success in preparing these two quaternary thioarsenates(III) proves that surfactant-thermal technique is a powerful yet facile synthetic method to explore new complex chalcogenides. - Graphical abstract: Two new quaternary thioarsenates(III) NaAg{sub 2}AsS{sub 3}·H{sub 2}O (1) and KAg{sub 2}AsS{sub 3} (2) with high yields have been successfully prepared through a facile surfactant-thermal method. X-ray single crystal diffraction analyses demonstrate that Na{sup +} and K{sup +} cations have different structure directing effects on these two thioarsenates(III). Both experimental and theoretical studies confirm 1 and 2 are semiconductors with band gaps in the visible region. Display Omitted - Highlights: • NaAg{sub 2}AsS{sub 3}⋅H{sub 2}O (1) and KAg{sub 2}AsS{sub 3} (2) were prepared through surfactant-thermal method. • Crystal structures show Na{sup ±} and K{sup ±} have different structure directing effects. • The weak basicity of solvent is benefit to the growth of 2 compared with 1. • Experimental and theoretical studies confirm 1 and 2 are semiconductors.« less

Topological control of supramolecular crystal structures of phenylene bis-monothiooxamate derivatives and in vitro anticancer activity

NASA Astrophysics Data System (ADS)

da Cunha, Tamyris T.; Oliveira, Willian X. C.; Marzano, Ivana M.; Pinheiro, Carlos B.; Pereira-Maia, Elene Cristina; Pereira, Cynthia L. M.

2017-12-01

This paper describes the synthesis, physical characterization, X-ray crystal structures and antitumoral activity against human carcionogenic cells of three new diethyl ester acid derivatives of phenylene bis-monothiooxamate compounds, namely Et2H2opbta (1), Et2H2mpbta (2) and Et2H2ppbta (3) [opbta = N,N‧-1,2-phenylenebis(2-thiooxamate), mbpta = N,N‧-1,3-phenylenebis(2-thiooxamate) and ppbta = N,N‧-1,4-phenylenebis(2-thiooxamate)]. Compounds 1-3 were obtained under mild conditions by reaction of the corresponding N,N‧-phenylenebis(oxamate) analogues and Lawesson's reagent resulting in the formation of Cdbnd S bonds at the carbonyl amide functions. Crystal structures of 1-3 consist of 1D supramolecular assemblies of centrosymmetric H2Et2ppbta (3) or noncentrosymmetric chiral H2Et2opbta (1) and H2Et2mpbta (2) molecules with opposite helical chirality (M and P enantiomers) resulting from intermolecular Nsbnd H⋯O (1 and 3) or Nsbnd H⋯S (2) hydrogen bonds between the amide hydrogen atoms and the carbonyl ester oxygen or thionyl amide sulfur atoms from the thiooxamate moieties respectively, together with weak S⋯S bonds between the thionyl amide sulfur atoms (1). The cytotoxicity of H2Et2xpbta [x = o (1), m (2) and p (3)] against chronic myelogenous leukemia cells was evaluated and the bioactivity follows the order 1 ≫ 2 > 3, compound 1 being six and ten times more active than 2 and 3, respectively.

Order-disorder structural phase transition and magnetocaloric effect in organic-inorganic halide hybrid (C2H5NH3)2CoCl4

NASA Astrophysics Data System (ADS)

Sen, Abhijit; Roy, Soumyabrata; Peter, Sebastian C.; Paul, Arpita; Waghmare, Umesh V.; Sundaresan, A.

2018-02-01

We report a detailed experimental and theoretical investigation of structural, optical, magnetic and magnetothermal properties of single crystals of a new organic-inorganic hybrid (C2H5NH3)2CoCl4. Grown by slow evaporation method at room temperature, the compound crystallizes in centrosymmetric orthorhombic structure (Pnma) which undergoes a reversible phase transition at 235/241 K (cooling/heating) to noncentrosymmetric P212121 space group symmetry associated with order-disorder transformation of carbon atoms of the ammonium cations as well as molecular rearrangement. Electronic absorption spectra of the compound are typical of geometrically distorted [CoCl4]2- tetrahedra having spin-orbit coupling effect. The isolated nature of [CoCl4]2- tetrahedra in the crystal reflect in paramagnetic behaviour of the compound. Interestingly, field induced spin flipping behaviour is observed at low temperature. First principles density functional calculations reveal weak magnetic interaction among cobalt spins with ferromagnetic state being the ground state. The entropy change associated with the spin flipping has been experimentally estimated by magnetic and heat capacity measurements which has a maximum value of 16 J Kg-1 K-1 at 2.5 K under 7 T magnetic field. To the best of our knowledge, this is the first report on magnetocaloric effect observed in an organic-inorganic halide compound. The estimated value is sizable and is comparable to that of well-known transition metal molecular cluster magnets Mn12 or Fe14. The overall findings promise to enlighten new routes to design and constitute multifunctional organic-inorganic halide materials.

Crystal structure of octa­kis­(4-meth­oxy­pyridinium) bis­(4-meth­oxy­pyridine-κN)tetra­kis­(thio­cyanato-κN)ferrate(III) bis­[(4-meth­oxypyri­dine-κN)pentakis­(thio­cyanato-κN)ferrate(III)] hexa­kis­(thio­cyanato-κN)ferrate(III) with iron in three different octa­hedral coordination environments

PubMed Central

Jochim, Aleksej; Jess, Inke; Näther, Christian

2018-01-01

The crystal structure of the title salt, (C6H8NO)8[Fe(NCS)4(C6H7NO)2][Fe(NCS)5(C6H7NO)]2[Fe(NCS)6], comprises three negatively charged octa­hedral FeIII complexes with different coordination environments in which the FeIII atoms are coordinated by a different number of thio­cyanate anions and 4-meth­oxy­pyridine ligands. Charge balance is achieved by 4-meth­oxy­pyridinium cations. The asymmetric unit consists of three FeIII cations, one of which is located on a centre of inversion, one on a twofold rotation axis and one in a general position, and ten thio­cyanate anions, two 4-meth­oxy­pyridine ligands and 4-meth­oxy­pyridinium cations (one of which is disordered over two sets of sites). Beside to Coulombic inter­actions between organic cations and the ferrate(III) anions, weak N—H⋯S hydrogen-bonding inter­actions involving the pyridinium N—H groups of the cations and the thio­cyanate S atoms of the complex anions are mainly responsible for the cohesion of the crystal structure. PMID:29765708

Two novel magnesium(II) meso-tetraphenylporphyrin-based coordination complexes: Syntheses, combined experimental and theoretical structures elucidation, spectroscopy, photophysical properties and antibacterial activity

NASA Astrophysics Data System (ADS)

Amiri, Nesrine; Hajji, Melek; Taheur, Fadia Ben; Chevreux, Sylviane; Roisnel, Thierry; Lemercier, Gilles; Nasri, Habib

2018-02-01

Two novel magnesium(II) tetraphenylporphyrin-based six-coordinate complexes; bis(hexamethylenetetramine)(5,10,15,2O tetrakis[4(benzoyloxy)phenyl]porphinato) magnesuim(II) (1) and bis(1,4-diazabicyclo(2.2.2)octane) (5,10,15,2O-tetrakis[4- (benzoyloxy)phenyl]porphinato)magnesium(II) (2) have been synthesised and confirmed by proton nuclear magnetic resonance, mass spectrometry, elemental analysis and IR spectroscopy. Both crystal structures were determined and described by single crystal X-ray diffraction analysis and Hirshfeld surfaces computational method. All Mg(II) atoms are surrounded by four porphyrin nitrogen atoms and two axial ligands coordinated to the metal ion through one nitrogen atom, forming a regular octahedron. In both complexes, molecular structures and three-dimensional framework are stabilised by inter-and intramolecular C-H ⋯O and C-H ⋯N hydrogen bonds, and by weak C-H ⋯Cg π interactions. UV-visible and Fluorescence investigations, respectively, show that studied complexes have a strong absorption in red part and exhibit an emission in the blue region. The HOMO-LUMO energy gap values, modelled using the DFT approach, indicates that both studied compounds can be classified as semiconductors. The role of these complexes as novel antibacterial agents was also performed.

Electronic Structure and Magnetic Interactions in the Radical Salt [BEDT-TTF]2[CuCl4].

PubMed

Calzado, Carmen J; Rodríguez-García, Bárbara; Galán Mascarós, José Ramón; Hernández, Norge Cruz

2018-06-07

The magnetic behavior and electric properties of the hybrid radical salt [BEDT-TTF] 2 [CuCl 4 ] have been revisited through extended experimental analyses and DDCI and periodic DFT plane waves calculations. Single crystal X-ray diffraction data have been collected at different temperatures, discovering a phase transition occurring in the 250-300 K range. The calculations indicate the presence of intradimer, interdimer, and organic-inorganic π-d interactions in the crystal, a magnetic pattern much more complex than the Bleaney-Bowers model initially assigned to this material. Although this simple model was good enough to reproduce the magnetic susceptibility data, our calculations demonstrate that the actual magnetic structure is significantly more intricate, with alternating antiferromagnetic 1D chains of the organic BEDT-TTF + radical, connected through weak antiferromagnetic interactions with the CuCl 4 2- ions. Combination of experiment and theory allowed us to unambiguously determine and quantify the leading magnetic interactions in the system. The density-of-states curves confirm the semiconductor nature of the system and the dominant organic contribution of the valence and conduction band edges. This general and combined approach appears to be fundamental in order to properly understand the magnetic structure of these complex materials, where experimental data can actually be fitted from a variety of models and parameters.

Evolution of magnetism in single-crystal C a 2 R u 1 - x I r x O 4 ( 0 ≤ x ≤ 0.65 )

DOE PAGES

Yuan, S. J.; Terzic, J.; Wang, J. C.; ...

2015-07-24

In this paper, we report structural, magnetic, transport, and thermal properties of single-crystal Ca 2Ru 1-xIr xO 4(0≤x≤0.65). Ca 2RuO 4 is a structurally driven Mott insulator with a metal-insulator transition at T MI=357K, which is well separated from antiferromagnetic order at T N=110K. Substitution of a 5d element, Ir, for Ru enhances spin-orbit coupling and locking between the structural distortions and magnetic moment canting. Ir doping intensifies the distortion or rotation of Ru/IrO 6 octahedra and induces weak ferromagnetic behavior along the c axis. In particular, Ir doping suppresses T N but concurrently causes an additional magnetic ordering Tmore » N2 at a higher temperature up to 210 K for x=0.65. The effect of Ir doping sharply contrasts with that of 3d-element doping such as Cr, Mn, and Fe, which suppresses T N and induces unusual negative volume thermal expansion. Finally, the stark difference between 3d- and 5d-element doping underlines a strong magnetoelastic coupling inherent in the Ir-rich oxides.« less

(E)-1,2-Bis(4-fluoro­phen­yl)ethane-1,2-dione

PubMed Central

Fun, Hoong-Kun; Kia, Reza

2008-01-01

The title compound, C14H8F2O2, is a substituted benzil with an s-trans conformation of the dicarbonyl unit. This conformation is also shown by the O—C—C—O torsion angle of −110.65 (12)°. An unusual feature of the structure is the length, 1.536 (2) Å, of the central C—C bond connecting the carbonyl units, which is significantly longer than a normal Csp 2—Csp 2 single bond. This is probably the result of decreasing the unfavourable vicinal dipole–dipole inter­actions by increasing the distance between the two electronegative O atoms [O⋯O = 3.1867 (12) Å] and allowing orbital overlap of the dione with the π system of the benzene rings. The dihedral angle between the aromatic rings is 64.74 (5)°. In the crystal structure, neighbouring mol­ecules are linked together by weak inter­molecular C—H⋯O (× 2) hydrogen bonds. In addition, the crystal structure is further stabilized by inter­molecular π–π inter­actions with centroid–centroid distances in the range 3.6416 (6)–3.7150 (7) Å. PMID:21203308

Crystal structure, vibrational and theoretical studies of bis(4-amino-1,2,4-triazolium) hexachloridostannate(IV)

NASA Astrophysics Data System (ADS)

Daszkiewicz, Marek; Marchewka, Mariusz K.

2012-06-01

X-ray structure of new hybrid organic-inorganic compound, bis(4-amino-1,2,4-triazolium) hexachloridostannate(IV), [1t(4at)]2SnCl6 (P1¯ space group) was determined. Crystal structure of 4-amino-1,2,4-triazole (Pbca space group) was reinvestigated. Non-planar orientation of NH2 group was found. The geometry of the amino group does not significantly change upon protonation. The route of protonation of 4-aminotriazole and tautomer equilibrium constants for the cationic forms were theoretically studied by means of B3LYP/6-31G* method. The most stable monoprotonated species is 1H-trans-4-amino-1,2,4-triazole, 1t(4at)+, whereas the final product of the protonation route is 12(4at)2+. Potential Energy Distribution (PED) analysis was carried out for two conformers, 1c(4at)+ and 1t(4at)+. Very good agreement between theoretical and experimental frequencies was achieved due to very weak interactions existing in [1t(4at)]2SnCl6. Infrared and Raman bands were assigned on the basis of PED analysis. Comparison of vibrational spectra of [1t(4at)]2SnCl6 and [1t(4at)]Cl indicates significantly weaker intermolecular interactions in the former compound.

Synthesis, Self-Assembly, and Drug-Release Properties of New Amphipathic Liquid Crystal Polycarbonates

PubMed Central

Xie, Yujiao; Liu, Xiaofeng; Hu, Zhuang; Hou, Zhipeng; Chen, Zhangpei; Hu, Jianshe; Yang, Liqun

2018-01-01

New amphiphilic liquid crystal (LC) polycarbonate block copolymers containing side-chain cholesteryl units were synthesized. Their structure, thermal stability, and LC phase behavior were characterized with Fourier transform infrared (FT-IR) spectrum, 1H NMR, gel permeation chromatographic (GPC), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), polarizing optical microscope (POM), and XRD methods. The results demonstrated that the LC copolymers showed a double molecular arrangement of a smectic A phase at room temperature. With the elevating of LC unit content in such LC copolymers, the corresponding properties including decomposition temperature (Td), glass temperature (Tg), and isotropic temperature (Ti) increased. The LC copolymers showed pH-responsive self-assembly behavior under the weakly acidic condition, and with more side-chain LC units, the self-assembly process was faster, and the formed particle size was smaller. It indicated that the self-assembly driving force was derived from the orientational ability of LC. The particle size and morphologies of self-assembled microspheres loaded with doxorubicin (DOX), together with drug release tracking, were evaluated by dynamic light scattering (DLS), SEM, and UV–vis spectroscopy. The results showed that DOX could be quickly released in a weakly acidic environment due to the pH response of the self-assembled microspheres. This would offer a new strategy for drug delivery in clinic applications. PMID:29584691

Systematic Approach to Electrostatically Induced 2D Crystallization of Nanoparticles at Liquid Interfaces

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fukuto, M.; Kewalramani, S.; Wang, S.

2011-02-07

We report an experimental demonstration of a strategy for inducing two-dimensional (2D) crystallization of charged nanoparticles on oppositely charged fluid interfaces. This strategy aims to maximize the interfacial adsorption of nanoparticles, and hence their lateral packing density, by utilizing a combination of weakly charged particles and a high surface charge density on the planar interface. In order to test this approach, we investigated the assembly of cowpea mosaic virus (CPMV) on positively charged lipid monolayers at the aqueous solution surface, by means of in situ X-ray scattering measurements at the liquid-vapor interface. The assembly was studied as a function ofmore » the solution pH, which was used to vary the charge on CPMV, and of the mole fraction of the cationic lipid in the binary lipid monolayer, which set the interface charge density. The 2D crystallization of CPMV occurred in a narrow pH range just above the particle's isoelectric point, where the particle charge was weakly negative, and only when the cationic-lipid fraction in the monolayer exceeded a threshold. The observed 2D crystals exhibited nearly the same packing density as the densest lattice plane within the known 3D crystals of CPMV. The above electrostatic approach of maximizing interfacial adsorption may provide an efficient route to the crystallization of nanoparticles at aqueous interfaces.« less

Experimental investigation of the dynamics of spontaneous pattern formation during dendritic ice crystal growth

NASA Astrophysics Data System (ADS)

Tirmizi, Shakeel H.; Gill, William N.

1989-06-01

The dynamics of spontaneous pattern formation are studied experimentally by observing and recording the evolution of ice crystal patterns which grow freely in a supercooled melt. The sequence of evolution to dendrites is recorded in real time using cine-micrography. In the range of subcoolings from 0.06 to 0.29°C, all the patterns evolved as follows: Smooth disk → Perturbed disk → Disk dendrite → Partially developed dendrite → Fully developed dendrite. The initial smooth disk, the main branch and the side branches all developed perturbations beyond a critical size which depends on the subcooling. The combined effect of the destabilizing thermal gradients ahead of the growing crystal and the stabilizing Gibbs-Thompson capillarity effect dictates the critical size of the unstable structures in terms of the mean curvature of the interface. Detailed analysis of the evolving patterns was done using digital image analysis on the PRIME computer to determine both the manner in which the dendritic growth process replicates itself and the role which the shape and the movement of the interface play in the pattern formation process. Total arc length ST, total area A and the complexity ratio ξ = ST⧸√ A of evolving patterns were computed as a function of time and undercooling for each crystal image. These results permitted us to make some comparisons with theoretical models on pattern evolution. Three distinct phases of evolution were identified: the initial phase when the crystal structure is smooth and free of any perturbations and the complexity ratio is almost a constant, an intermediate phase when the crystal structure develops perturbations which grow quickly in number and in size and the complexity ratio increases rapidly and a final phase when the pattern approaches that of a fully developed dendrite which, on a global scale grows in a shape-perserving manner and has a slowly increasing complexity ratio which seems to approach an asymptote. Two factors were found to be responsible for the symmetric dendritic patterns. These are: first, hexagonal symmetry due to the hexagonal closed packed structure, leads to strong anisotropy in molecular attachment kinetics and in surface free energy; second, the competition among side branches causes smaller side branches to melt when they are trapped between larger ones which generate latent heat and prevent the small branches from gaining access to the fresh cold fluid ahead of them. These two factors lead to a channelling effect which prevents the growth of perturbations from occurring randomly and thus directs the evolving crystal structure into patterns which are regular and reproducible. Theoretical models which are local in nature fail to take into account side branch competition, and this is one of their major weaknesses.

Sesquiterpene lactones from Gynoxys verrucosa and their anti-MRSA activity.

PubMed

Ordóñez, Paola E; Quave, Cassandra L; Reynolds, William F; Varughese, Kottayil I; Berry, Brian; Breen, Philip J; Malagón, Omar; Smeltzer, Mark S; Compadre, Cesar M

2011-09-02

Because of its virulence and antibiotic resistance, Staphylococcus aureus is a more formidable pathogen now than at any time since the pre-antibiotic era. In an effort to identify and develop novel antimicrobial agents with activity against this pathogen, we have examined Gynoxys verrucosa Wedd (Asteraceae), an herb used in traditional medicine in southern Ecuador for the treatment and healing of wounds. The sesquiterpene lactones leucodine (1) and dehydroleucodine (2) were extracted and purified from the aerial parts of Gynoxys verrucosa, and their structure was elucidated by spectroscopic methods and single-crystal X-ray analysis. The in vitro anti-microbial activity of Gynoxys verrucosa extracts and its purified constituents was determined against six clinical isolates including Staphylococcus aureus and Staphylococcus epidermidis strains with different drug-resistance profiles, using the microtiter broth method. Compound 1 has very low activity, while compound 2 has moderate activity with MIC(50)s between 49 and 195 μg/mL. The extract of Gynoxys verrucosa has weak activity with MIC(50)s between 908 and 3290 μg/mL. We are reporting the full assignment of the (1)H NMR and (13)C NMR of both compounds, and the crystal structure of compound 2, for the first time. Moreover, the fact that compound 2 has antimicrobial activity and compound 1 does not, demonstrates that the exocyclic conjugated methylene in the lactone ring is essential for the antimicrobial activity of these sesquiterpene lactones. However, the weak activity observed for the plant extracts, does not explain the use of Gynoxys verrucosa in traditional medicine for the treatment of wounds and skin infections. Copyright © 2011 Elsevier Ireland Ltd. All rights reserved.

Reactive p-block cations stabilized by weakly coordinating anions

PubMed Central

Engesser, Tobias A.; Lichtenthaler, Martin R.; Schleep, Mario

2016-01-01

The chemistry of the p-block elements is a huge playground for fundamental and applied work. With their bonding from electron deficient to hypercoordinate and formally hypervalent, the p-block elements represent an area to find terra incognita. Often, the formation of cations that contain p-block elements as central ingredient is desired, for example to make a compound more Lewis acidic for an application or simply to prove an idea. This review has collected the reactive p-block cations (rPBC) with a comprehensive focus on those that have been published since the year 2000, but including the milestones and key citations of earlier work. We include an overview on the weakly coordinating anions (WCAs) used to stabilize the rPBC and give an overview to WCA selection, ionization strategies for rPBC-formation and finally list the rPBC ordered in their respective group from 13 to 18. However, typical, often more organic ion classes that constitute for example ionic liquids (imidazolium, ammonium, etc.) were omitted, as were those that do not fulfill the – naturally subjective – “reactive”-criterion of the rPBC. As a rule, we only included rPBC with crystal structure and only rarely refer to important cations published without crystal structure. This collection is intended for those who are simply interested what has been done or what is possible, as well as those who seek advice on preparative issues, up to people having a certain application in mind, where the knowledge on the existence of a rPBC that might play a role as an intermediate or active center may be useful. PMID:26612538

Sesquiterpene Lactones from Gynoxys verrucosa and their Anti-MRSA Activity

PubMed Central

Ordóñez, Paola E.; Quave, Cassandra L.; Reynolds, William F.; Varughese, Kottayil I.; Berry, Brian; Breen, Philip J.; Malagón, Omar; Smeltzer, Mark S.; Compadre, Cesar M.

2011-01-01

Ethnopharmacological relevance Because of its virulence and antibiotic resistance, Staphylococcus aureus is a more formidable pathogen now than at any time since the pre-antibiotic era. In an effort to identify and develop novel antimicrobial agents with activity against this pathogen, we have examined Gynoxys verrucosa Wedd (Asteraceae), an herb used in traditional medicine in southern Ecuador for the treatment and healing of wounds. Materials and Methods The sesquiterpene lactones leucodine (1) and dehydroleucodine (2) were extracted and purified from the aerial parts of G. verrucosa, and their structure was elucidated by spectroscopic methods and single-crystal X-ray analysis. The in vitro anti-microbial activity of G. verrucosa extracts and its purified constituents was determined against six clinical isolates including S. aureus and Staphylococcus epidermidis strains with different drug-resistance profiles, using the microtiter broth method. Results Compound 1 has very low activity, while compound 2 has moderate activity with MIC50s between 49 and195 μg/mL. The extract of G. verrucosa has weak activity with MIC50s between 908 and 3290 μg/mL. Conclusions We are reporting the full assignment of the 1H-NMR and 13C-NMR of both compounds, and the crystal structure of compound 2, for the first time. Moreover, the fact that compound 2 has antimicrobial activity and compound 1 does not, demonstrates that the exocyclic conjugated methylene in the lactone ring is essential for the antimicrobial activity of these sesquiterpene lactones. However, the weak activity observed for the plants extracts, does not explain the use of G. verrucosa in traditional medicine for the treatment of wounds and skin infections. PMID:21782013

3-Methylthio-4-phenyl-5-phenylamino-1,2,4-triazole hexabromotellurate:X-ray and computational study

NASA Astrophysics Data System (ADS)

Fizer, Maksym; Slivka, Mikhailo; Mariychuk, Ruslan; Baumer, Vjacheslav; Lendel, Vasil

2018-06-01

The structure of a newly synthesized 3-methylthio-4-phenyl-5-phenylamino-1,2,4-triazole 1 and its hexabromotellurate salt 2 was investigated. The X-ray diffraction study of 2 gives the insight on the different interaction types in the crystal. The DFT calculations were used for the comprehensive study of the intramolecular and intermolecular forces that are present in the title 3-methylthio-4-phenyl-5-phenylamino-1,2,4-triazole hexabromotellurate. The presence of three different aromatic moieties in the investigated compounds cause π-π stacking interactions which were studied through the Hirshfeld surface analysis and with the discrimination of weak interaction types by filling color to a reduced density gradient (RDG) function isosurface. The RDG in the crystalline state was calculated upon experimental molecular geometry by partitions of the crystal to QM part that was calculated at M06-L/6-311G(d,p) level, and the semi-empirical QM part that was modeled with the PM7 method in QM/MM-like manner. The reactivity of 3-methylthio-4-phenyl-5-phenylamino-1,2,4-triazole and its protonated form was also discussed in terms of conceptual DFT theory and it shows the tendency of sulfur to be the most active center in an electrophilic and radical attack, whereas the site for nucleophilic substitution is medium dependent and not an unequivocal. NICS(1) index was used for the analysis of aromaticity of three different cyclic moieties. The present study insights the changes in the structure of a polyfunctional substituted triazole upon its protonation and explains these changes with the analysis of weak interactions.

Patterns of Cognitive Strengths and Weaknesses and Relationships to Math Errors

ERIC Educational Resources Information Center

Koriakin, Taylor; White, Erica; Breaux, Kristina C.; DeBiase, Emily; O'Brien, Rebecca; Howell, Meiko; Costa, Michael; Liu, Xiaochen; Pan, Xingyu; Courville, Troy

2017-01-01

This study investigated cognitive patterns of strengths and weaknesses (PSW) and their relationship to patterns of math errors on the Kaufman Test of Educational Achievement (KTEA-3). Participants, ages 5 to 18, were selected from the KTEA-3 standardization sample if they met one of two PSW profiles: high crystallized ability (Gc) paired with low…

Weakly-bridged dimeric diorganotin(IV) compounds derived from pyruvic acid hydrazone Schiff base ligands: Synthesis, characterization and crystal structures

NASA Astrophysics Data System (ADS)

Hong, Min; Yin, Han-Dong; Cui, Ji-Chun

2011-03-01

We report the synthesis of four diorganotin(IV) compounds of Schiff base pyruvic acid hydrazone derivatives formulated as [R 2SnLY] 2, where L 1 is 2-SC 4H 3CON 2C(CH 3)CO 2 with Y = CH 3CH 2CH 2CH 2OH, R = n-Bu ( 1); L 2 is C 6H 5CON 2C(CH 3)CO 2 with Y = CH 3CH 2OH, R = p-F-Bz ( 2); L 3 is 2-HOC 6H 4CON 2C(CH 3)CO 2 with Y dbnd H 2O, R = p-CN -Bz ( 3); and L 4 is 4-NO 2-C 6H 4CON 2C(CH 3)CO 2 with Y dbnd CH 3CH 2OH, R = Bz ( 4). The structures of all compounds have been established by a combination of single-crystal X-ray diffraction analysis, 1H and 119Sn NMR spectroscopy, IR spectroscopy, and elemental analysis. Studies reveal that four ligands present the same coordination mode with tin center, which all present tridentate ONO donor Schiff bases and coordinate to the tin center in an enolic form. In compounds 1- 4, each tin atom is seven-coordinated and exhibits a distorted pentagonal bipyramid with a planar SnO 4N unit and two apical alkyl carbon atoms, thus forming a weakly-bridged dimeric molecule. Additionally, the distance of Sn⋯O bridge in each compound is obviously affected by the choice of different alkyl groups and coordination solvent molecules, which fluctuates in the range of 2.571(5)-2.839(4) Å. Furthermore, the supramolecular structure analysis show that there are two types of supramolecular infrastructures, 1D chain or 2D network, which are formed by intermolecular O-H···N or C-H⋯X (X = O, N or F) hydrogen bonds.

Correlation and the mechanism of lithium ion diffusion with the crystal structure of Li7La3Zr2O12 revealed by an internal friction technique.

PubMed

Wang, X P; Gao, Y X; Xia, Y P; Zhuang, Z; Zhang, T; Fang, Q F

2014-04-21

The correlation and transport mechanism of lithium ions with the crystal structure of a fast lithium ion conductor Li7La3Zr2O12 are mainly investigated by internal friction (IF) and AC impedance spectroscopy techniques. Compared with the poor conductivity of tetragonal Li7La3Zr2O12, the Al stabilized cubic phase exhibits a good ionic conductivity that can be up to 1.9 × 10(-4) S cm(-1) at room temperature, which can be ascribed to the disordered distribution of lithium ions in the cubic phase. A well-pronounced relaxation IF peak (labeled as peak PC) is observed in the cubic phase while a very weak IF peak (labeled as PT) is observed in the tetragonal phase, further evidencing the difference in lithium ion migration in the two phases. Peak PC can be decomposed into two sub-peaks with the activation energy and the pre-exponential factor of relaxation time being E1 = 0.41 eV and τ01 = 1.2 × 10(-14) s for the lower temperature peak PC1 and E2 = 0.35 eV and τ02 = 1.9 × 10(-15) s for the higher temperature PC2 peak, respectively. Based on the crystalline structure of a cubic garnet-type Li7La3Zr2O12 compound, an atomistic mechanism of lithium ion diffusion via vacancies is suggested, i.e. 48g(96h) ↔ 48g(96h) for peak PC1 and 48g(96h) ↔ 24d for peak PC2, respectively. The weak PT peak in the tetragonal phase is preliminarily interpreted as due to the short jump process among neighboring octahedral sites and vacant tetrahedral sites.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Patel, J. R.

We synthesized hexagonal-disc-shaped MgB{sub 2} single crystals under high-pressure conditions and analyzed the microstructure and pinning properties. The lattice constants and the Laue pattern of the crystals from X-ray micro-diffraction showed the crystal symmetry of MgB{sub 2}. A thorough crystallographic mapping within a single crystal showed that the edge and c-axis of hexagonal-disc shape exactly matched the (10-10) and the (0001) directions of the MgB{sub 2} phase. Thus, these well-shaped single crystals may be the best candidates for studying the direction dependences of the physical properties. The magnetization curve and the magnetic hysteresis for these single crystals showed the existencemore » of a wide reversible region and weak pinning properties, which supported our single crystals being very clean.« less

Eight supramolecular assemblies constructed from bis(benzimidazole) and organic acids through strong classical hydrogen bonding and weak noncovalent interactions

NASA Astrophysics Data System (ADS)

Jin, Shouwen; Wang, Daqi

2014-05-01

Eight crystalline organic acid-base adducts derived from alkane bridged bis(N-benzimidazole) and organic acids (2,4,6-trinitrophenol, p-nitrobenzoic acid, m-nitrobenzoic acid, 3,5-dinitrobenzoic acid, 5-sulfosalicylic acid and oxalic acid) were prepared and characterized by X-ray diffraction analysis, IR, mp, and elemental analysis. Of the eight compounds five are organic salts (1, 4, 6, 7 and 8) and the other three (2, 3, and 5) are cocrystals. In all of the adducts except 1 and 8, the ratio of the acid and the base is 2:1. All eight supramolecular assemblies involve extensive intermolecular classical hydrogen bonds as well as other noncovalent interactions. The role of weak and strong noncovalent interactions in the crystal packing is ascertained. These weak interactions combined, all the complexes displayed 3D framework structure. The results presented herein indicate that the strength and directionality of the classical N+-H⋯O-, O-H⋯O, and O-H⋯N hydrogen bonds (ionic or neutral) and other nonbonding associations between acids and ditopic benzimidazoles are sufficient to bring about the formation of cocrystals or organic salts.

Antiparallel Self-Association of a γ,α-Hybrid Peptide: More Relevance of Weak Interactions.

PubMed

Venugopalan, Paloth; Kishore, Raghuvansh

2015-08-01

To learn how a preorganized peptide-based molecular template, together with diverse weak non-covalent interactions, leads to an effective self-association, we investigated the conformational characteristics of a simple γ,α-hybrid model peptide, Boc-γ-Abz-Gly-OMe. The single-crystal X-ray diffraction analysis revealed the existence of a fully extended β-strand-like structure stabilized by two non-conventional C-H⋅⋅⋅O=C intramolecular H-bonds. The 2D (1) H NMR ROESY experiment led us to propose that the flat topology of the urethane-γ-Abz-amide moiety is predominantly preserved in a non-polar environment. The self-association of the energetically more favorable antiparallel β-strand-mimic in solid-state engenders an unusual 'flight of stairs' fabricated through face-to-face and edge-to-edge Ar⋅⋅⋅Ar interactions. In conjunction with FT-IR spectroscopic analysis in chloroform, we highlight that conformationally semi-rigid γ-Abz foldamer in appositely designed peptides may encourage unusual β-strand or β-sheet-like self-association and supramolecular organization stabilized via weak attractive forces. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Negative and positive magnetoresistance in GaInNAs/GaAs modulation-doped quantum well structures

NASA Astrophysics Data System (ADS)

Nutku, Ferhat; Donmez, Omer; Sarcan, Fahrettin; Erol, Ayşe; Puustinen, Janne; Arıkan, Mehmet Çetin; Guina, Mircea

2015-03-01

In this work, magnetoresistance of as-grown and annealed n- and p-type modulation-doped Ga0.68In0.32NyAs1-y/GaAs single quantum well structures with various nitrogen concentrations has been studied. At low temperatures and low magnetic fields, in n-type samples negative and in p-type samples positive, magnetoresistance has been observed. The observed negative magnetoresistance in n-type samples is an indication of enhanced backscattering of electrons due to the weak localization of the electrons as an effect of the N-induced defects. Nitrogen concentration and thermal annealing dependence of the magnetoresistance have been studied for both n- and p-type samples. The observed decrease in the negative magnetoresistance in n-type and enhanced positive magnetoresistance in p-type samples following thermal annealing have been explained by considering thermal annealing-induced improvement of mobility and the crystal quality in N-containing samples. After thermal annealing, the magnitude of negative magnetoresistance decreases and the breaking of the weak localization is achieved at lower magnetic fields in n-type samples. It is observed that as the mobility of the sample increases, critical magnetic field of negative to positive magnetoresistance transition becomes lower.

Dynamical correlation effects in a weakly correlated material: Inelastic x-ray scattering and photoemission spectra of beryllium

NASA Astrophysics Data System (ADS)

Seidu, Azimatu; Marini, Andrea; Gatti, Matteo

2018-03-01

Beryllium is a weakly correlated simple metal. Still we find that dynamical correlation effects, beyond the independent-particle picture, are necessary to successfully interpret the electronic spectra measured by inelastic x-ray scattering (IXS) and photoemission spectroscopies (PES). By combining ab initio time-dependent density-functional theory (TDDFT) and many-body Green's function theory in the G W approximation (G W A ), we calculate the dynamic structure factor, the quasiparticle (QP) properties and PES spectra of bulk Be. We show that band-structure effects (i.e., due to interaction with the crystal potential) and QP lifetimes (LT) are both needed in order to explain the origin of the measured double-peak features in the IXS spectra. A quantitative agreement with experiment is obtained only when LT are supplemented to the adiabatic local-density approximation (ALDA) of TDDFT. Besides the valence band, PES spectra display a satellite, a signature of dynamical correlation due to the coupling of QPs and plasmons, which we are able to reproduce thanks to the combination of the G W A for the self-energy with the cumulant expansion of the Green's function.

Design of Bcl-2 and Bcl-xL Inhibitors with Subnanomolar Binding Affinities Based upon a New Scaffold

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhou, Haibin; Chen, Jianfang; Meagher, Jennifer L.

Employing a structure-based strategy, we have designed a new class of potent small-molecule inhibitors of the anti-apoptotic proteins Bcl-2 and Bcl-xL. An initial lead compound with a new scaffold was designed based upon the crystal structure of Bcl-xL and U.S. Food and Drug Administration (FDA) approved drugs and was found to have an affinity of 100 {micro}M for both Bcl-2 and Bcl-xL. Linking this weak lead to another weak-affinity fragment derived from Abbott's ABT-737 led to an improvement of the binding affinity by a factor of >10,000. Further optimization ultimately yielded compounds with subnanomolar binding affinities for both Bcl-2 andmore » Bcl-xL and potent cellular activity. The best compound (21) binds to Bcl-xL and Bcl-2 with K{sub i} < 1 nM, inhibits cell growth in the H146 and H1417 small-cell lung cancer cell lines with IC{sub 50} values of 60-90 nM, and induces robust cell death in the H146 cancer cell line at 30-100 nM.« less

N-(sulfoethyl) iminodiacetic acid-based lanthanide coordination polymers: Synthesis, magnetism and quantum Monte Carlo studies

NASA Astrophysics Data System (ADS)

Zhuang, Gui-lin; Chen, Wu-lin; Zheng, Jun; Yu, Hui-you; Wang, Jian-guo

2012-08-01

A series of lanthanide coordination polymers have been obtained through the hydrothermal reaction of N-(sulfoethyl) iminodiacetic acid (H3SIDA) and Ln(NO3)3 (Ln=La, 1; Pr, 2; Nd, 3; Gd, 4). Crystal structure analysis exhibits that lanthanide ions affect the coordination number, bond length and dimension of compounds 1-4, which reveal that their structure diversity can be attributed to the effect of lanthanide contraction. Furthermore, the combination of magnetic measure with quantum Monte Carlo(QMC) studies exhibits that the coupling parameters between two adjacent Gd3+ ions for anti-anti and syn-anti carboxylate bridges are -1.0×10-3 and -5.0×10-3 cm-1, respectively, which reveals weak antiferromagnetic interaction in 4.

Two novel FeII-oxalate architectures: Solvent-free synthesis, structures, thermal and magnetic studies

NASA Astrophysics Data System (ADS)

Li, Jin-Hua; Liu, Hui; Wei, Li; Wang, Guo-Ming

2015-10-01

Two novel FeII-oxalate framework with the formulas of [NH4][FeIILi3(C2O4)3] (1) and [NH4]2[FeII(C2O4)2]·H2O (2) have been prepared by an oxalic acid flux approach and structurally characterized by IR, elemental analysis, thermogravimetric analysis, single-crystal and powder X-ray diffraction. Heterometallic compound 1 displays a three-dimensional (3D) framework with a pto topology, while homometallic compound 2 features a pillar-layer architecture with a hms topology. Thermal analysis indicates that the two compounds can be stable up to 300 °C and 200 °C, respectively. Magnetic investigations suggest that the FeII ions in 1 and 2 exhibit weak magnetic exchange interactions.

Bioinspired large-scale aligned porous materials assembled with dual temperature gradients

PubMed Central

Bai, Hao; Chen, Yuan; Delattre, Benjamin; Tomsia, Antoni P.; Ritchie, Robert O.

2015-01-01

Natural materials, such as bone, teeth, shells, and wood, exhibit outstanding properties despite being porous and made of weak constituents. Frequently, they represent a source of inspiration to design strong, tough, and lightweight materials. Although many techniques have been introduced to create such structures, a long-range order of the porosity as well as a precise control of the final architecture remain difficult to achieve. These limitations severely hinder the scale-up fabrication of layered structures aimed for larger applications. We report on a bidirectional freezing technique to successfully assemble ceramic particles into scaffolds with large-scale aligned, lamellar, porous, nacre-like structure and long-range order at the centimeter scale. This is achieved by modifying the cold finger with a polydimethylsiloxane (PDMS) wedge to control the nucleation and growth of ice crystals under dual temperature gradients. Our approach could provide an effective way of manufacturing novel bioinspired structural materials, in particular advanced materials such as composites, where a higher level of control over the structure is required. PMID:26824062

Efficient linear phase contrast in scanning transmission electron microscopy with matched illumination and detector interferometry

DOE PAGES

Ophus, Colin; Ciston, Jim; Pierce, Jordan; ...

2016-02-29

The ability to image light elements in soft matter at atomic resolution enables unprecedented insight into the structure and properties of molecular heterostructures and beam-sensitive nanomaterials. In this study, we introduce a scanning transmission electron microscopy technique combining a pre-specimen phase plate designed to produce a probe with structured phase with a high-speed direct electron detector to generate nearly linear contrast images with high efficiency. We demonstrate this method by using both experiment and simulation to simultaneously image the atomic-scale structure of weakly scattering amorphous carbon and strongly scattering gold nanoparticles. Our method demonstrates strong contrast for both materials, makingmore » it a promising candidate for structural determination of heterogeneous soft/hard matter samples even at low electron doses comparable to traditional phase-contrast transmission electron microscopy. Ultimately, simulated images demonstrate the extension of this technique to the challenging problem of structural determination of biological material at the surface of inorganic crystals.« less

Efficient linear phase contrast in scanning transmission electron microscopy with matched illumination and detector interferometry.

PubMed

Ophus, Colin; Ciston, Jim; Pierce, Jordan; Harvey, Tyler R; Chess, Jordan; McMorran, Benjamin J; Czarnik, Cory; Rose, Harald H; Ercius, Peter

2016-02-29

The ability to image light elements in soft matter at atomic resolution enables unprecedented insight into the structure and properties of molecular heterostructures and beam-sensitive nanomaterials. In this study, we introduce a scanning transmission electron microscopy technique combining a pre-specimen phase plate designed to produce a probe with structured phase with a high-speed direct electron detector to generate nearly linear contrast images with high efficiency. We demonstrate this method by using both experiment and simulation to simultaneously image the atomic-scale structure of weakly scattering amorphous carbon and strongly scattering gold nanoparticles. Our method demonstrates strong contrast for both materials, making it a promising candidate for structural determination of heterogeneous soft/hard matter samples even at low electron doses comparable to traditional phase-contrast transmission electron microscopy. Simulated images demonstrate the extension of this technique to the challenging problem of structural determination of biological material at the surface of inorganic crystals.

Efficient linear phase contrast in scanning transmission electron microscopy with matched illumination and detector interferometry

PubMed Central

Ophus, Colin; Ciston, Jim; Pierce, Jordan; Harvey, Tyler R.; Chess, Jordan; McMorran, Benjamin J.; Czarnik, Cory; Rose, Harald H.; Ercius, Peter

2016-01-01

The ability to image light elements in soft matter at atomic resolution enables unprecedented insight into the structure and properties of molecular heterostructures and beam-sensitive nanomaterials. In this study, we introduce a scanning transmission electron microscopy technique combining a pre-specimen phase plate designed to produce a probe with structured phase with a high-speed direct electron detector to generate nearly linear contrast images with high efficiency. We demonstrate this method by using both experiment and simulation to simultaneously image the atomic-scale structure of weakly scattering amorphous carbon and strongly scattering gold nanoparticles. Our method demonstrates strong contrast for both materials, making it a promising candidate for structural determination of heterogeneous soft/hard matter samples even at low electron doses comparable to traditional phase-contrast transmission electron microscopy. Simulated images demonstrate the extension of this technique to the challenging problem of structural determination of biological material at the surface of inorganic crystals. PMID:26923483

On vital aid: the why, what and how of validation

PubMed Central

Kleywegt, Gerard J.

2009-01-01

Limitations to the data and subjectivity in the structure-determination process may cause errors in macromolecular crystal structures. Appropriate validation techniques may be used to reveal problems in structures, ideally before they are analysed, published or deposited. Additionally, such tech­niques may be used a posteriori to assess the (relative) merits of a model by potential users. Weak validation methods and statistics assess how well a model reproduces the information that was used in its construction (i.e. experimental data and prior knowledge). Strong methods and statistics, on the other hand, test how well a model predicts data or information that were not used in the structure-determination process. These may be data that were excluded from the process on purpose, general knowledge about macromolecular structure, information about the biological role and biochemical activity of the molecule under study or its mutants or complexes and predictions that are based on the model and that can be tested experimentally. PMID:19171968

Synthesis, structure, and magnetic characterization of Cr{sub 4}US{sub 8}

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ward, Matthew D.; Chan, Ian Y.; Malliakas, Christos D.

The compound Cr{sub 4}US{sub 8} has been synthesized at 1073 K and its crystal structure has been determined at 100 K. The structure is modulated with a two-fold commensurate supercell. The subcell may be indexed in an orthorhombic cell but weak supercell reflections lead to the monoclinic superspace group P2{sub 1}/c(α0γ)0s with two Cr sites, one U site, and four S sites. The structure comprises a three-dimensional framework of CrS{sub 6} octahedra with channels that are partially occupied by U atoms. Each U atom in these channels is coordinated by eight S atoms in a bicapped trigonal-prismatic arrangement. The magneticmore » behavior of Cr{sub 4}US{sub 8} is complex. At temperatures above ~120 K at all measured fields, there is little difference between field-cooled and zero field-cooled data and χ(T) decreases monotonously with temperature, which is reminiscent of the Curie–Weiss law. At lower temperatures, the temperature dependence of χ(T) is complex and strongly dependent on the magnetic field strength. - Graphical abstract: Structure of Cr{sub 4}US{sub 8} viewed down the a axis. - Highlights: • At 1073 K Cr{sub 4}US{sub 8} was synthesized and at 100 K its crystal structure was determined. • The 3D structure comprises CrS{sub 6} octahedra with channels partially occupied by U. • The magnetic behavior of Cr{sub 4}US{sub 8} is complex.« less