Science.gov

Sample records for materials crystal structure

  1. Materials research at Stanford University. [composite materials, crystal structure, acoustics

    NASA Technical Reports Server (NTRS)

    1975-01-01

    Research activity related to the science of materials is described. The following areas are included: elastic and thermal properties of composite materials, acoustic waves and devices, amorphous materials, crystal structure, synthesis of metal-metal bonds, interactions of solids with solutions, electrochemistry, fatigue damage, superconductivity and molecular physics and phase transition kinetics.

  2. Solar cell structure incorporating a novel single crystal silicon material

    DOEpatents

    Pankove, Jacques I.; Wu, Chung P.

    1983-01-01

    A novel hydrogen rich single crystal silicon material having a band gap energy greater than 1.1 eV can be fabricated by forming an amorphous region of graded crystallinity in a body of single crystalline silicon and thereafter contacting the region with atomic hydrogen followed by pulsed laser annealing at a sufficient power and for a sufficient duration to recrystallize the region into single crystal silicon without out-gassing the hydrogen. The new material can be used to fabricate semiconductor devices such as single crystal silicon solar cells with surface window regions having a greater band gap energy than that of single crystal silicon without hydrogen.

  3. Advancements in the Quantification of the Crystal Structure of ZNS Materials Produced in Variable Gravity

    NASA Astrophysics Data System (ADS)

    Castillo, Martin

    2016-07-01

    Screens and displays consume tremendous amounts of power. Global trends to significantly consume less power and increase battery life have led to the reinvestigation of electroluminescent materials. The state of the art in ZnS materials has not been furthered in the past 30 years and there is much potential in improving electroluminescent properties of these materials with advanced processing techniques. Self-propagating high temperature synthesis (SHS) utilises a rapid exothermic process involving high energy and nonlinearity coupled with a high cooling rate to produce materials formed outside of normal equilibrium boundaries thus possessing unique properties. The elimination of gravity during this process allows capillary forces to dominate mixing of the reactants which results in a superior and enhanced homogeneity in the product materials. ZnS type materials have been previously conducted in reduced gravity and normal gravity. It has been claimed in literature that a near perfect phases of ZnS wurtzite was produced. Although, the SHS of this material is possible at high pressures, there has been no quantitative information on the actual crystal structures and lattice parameters that were produced in this work. Utilising this process with ZnS doped with Cu, Mn, or rare earth metals such as Eu and Pr leads to electroluminescence properties, thus making this an attractive electroluminescent material. The work described here will revisit the synthesis of ZnS via high pressure SHS and will re-examine the work performed in both normal gravity and in reduced gravity within the ZARM drop tower facility. Quantifications in the lattice parameters, crystal structures, and phases produced will be presented to further explore the unique structure-property performance relationships produced from the SHS of ZnS materials.

  4. Theoretical Studies on the Electronic Structures and Properties of Complex Ceramic Crystals and Novel Materials

    SciTech Connect

    Ching, Wai-Yim

    2012-01-14

    This project is a continuation of a long program supported by the Office of Basic Energy Science in the Office of Science of DOE for many years. The final three-year continuation started on November 1, 2005 with additional 1 year extension to October 30, 2009. The project was then granted a two-year No Cost Extension which officially ended on October 30, 2011. This report covers the activities within this six year period with emphasis on the work completed within the last 3 years. A total of 44 papers with acknowledgement to this grant were published or submitted. The overall objectives of this project are as follows. These objectives have been evolved over the six year period: (1) To use the state-of-the-art computational methods to investigate the electronic structures of complex ceramics and other novel crystals. (2) To further investigate the defects, surfaces/interfaces and microstructures in complex materials using large scale modeling. (3) To extend the study on ceramic materials to more complex bioceramic crystals. (4) To initiate the study on soft condensed matters including water and biomolecules. (5) To focus on the spectroscopic studies of different materials especially on the ELNES and XANES spectral calculations and their applications related to experimental techniques. (6) To develop and refine computational methods to be effectively executed on DOE supercomputers. (7) To evaluate mechanical properties of different crystals and those containing defects and relate them to the fundamental electronic structures. (8) To promote and publicize the first-principles OLCAO method developed by the PI (under DOE support for many years) for applications to large complex material systems. (9) To train a new generation of graduate students and postdoctoral fellows in modern computational materials science and condensed matter physics. (10) To establish effective international and domestic collaborations with both experimentalists and theorists in materials

  5. Synthesis, growth, structure and characterization of chalcone crystal: A novel organic NLO material

    NASA Astrophysics Data System (ADS)

    Agilandeshwari, R.; Meenatchi, V.; Meenakshisundaram, S. P.

    2016-08-01

    Single crystals of a chalcone, (E)-3-(4-bromophenyl)-1-(2-hydroxyphenyl)prop-2-en-1-one (BHP), were grown by the slow evaporation solution growth technique. The structure is elucidated by single-crystal X-ray diffraction analysis and the crystal belongs to the monoclinic system with noncentrosymmetric space group P21. Optical studies reveal that the absorption is minimum in the visible region and the cut-off wavelength is at ∼468 nm. The band-gap energy was estimated by the application of the Kubelka-Munk algorithm. The powder X-ray diffraction pattern reveals the good crystallinity of the as-grown specimen. The vibrational patterns in FT-IR are used to identify the functional groups and thermal studies indicate the stability of the material. The second harmonic generation efficiency (SHG), as estimated by Kurtz and Perry powder technique, reveals the superior nonlinear optical character of this material. Hirshfeld surface analysis is done to quantify the intermolecular interactions, responsible for developing a nonlinear atmosphere. As-grown crystals were further characterized by SEM, NMR, mass spectrometry and elemental analysis.

  6. Synthesis, growth, structure and characterization of chalcone crystal: A novel organic NLO material

    NASA Astrophysics Data System (ADS)

    Agilandeshwari, R.; Meenatchi, V.; Meenakshisundaram, S. P.

    2016-08-01

    Single crystals of a chalcone, (E)-3-(4-bromophenyl)-1-(2-hydroxyphenyl)prop-2-en-1-one (BHP), were grown by the slow evaporation solution growth technique. The structure is elucidated by single-crystal X-ray diffraction analysis and the crystal belongs to the monoclinic system with noncentrosymmetric space group P21. Optical studies reveal that the absorption is minimum in the visible region and the cut-off wavelength is at ∼468 nm. The band-gap energy was estimated by the application of the Kubelka-Munk algorithm. The powder X-ray diffraction pattern reveals the good crystallinity of the as-grown specimen. The vibrational patterns in FT-IR are used to identify the functional groups and thermal studies indicate the stability of the material. The second harmonic generation efficiency (SHG), as estimated by Kurtz and Perry powder technique, reveals the superior nonlinear optical character of this material. Hirshfeld surface analysis is done to quantify the intermolecular interactions, responsible for developing a nonlinear atmosphere. As-grown crystals were further characterized by SEM, NMR, mass spectrometry and elemental analysis.

  7. Advanced thermoelectric materials with enhanced crystal lattice structure and methods of preparation

    NASA Technical Reports Server (NTRS)

    Fleurial, Jean-Pierre (Inventor); Caillat, Thierry F. (Inventor); Borshchevsky, Alexander (Inventor)

    1998-01-01

    New skutterudite phases including Ru.sub.0.5 Pd.sub.0.5 Sb.sub.3, RuSb.sub.2 Te, and FeSb.sub.2 Te, have been prepared having desirable thermoelectric properties. In addition, a novel thermoelectric device has been prepared using skutterudite phase Fe.sub.0.5 Ni.sub.0.5 Sb.sub.3. The skutterudite-type crystal lattice structure of these semiconductor compounds and their enhanced thermoelectric properties results in semiconductor materials which may be used in the fabrication of thermoelectric elements to substantially improve the efficiency of the resulting thermoelectric device. Semiconductor materials having the desired skutterudite-type crystal lattice structure may be prepared in accordance with the present invention by using powder metallurgy techniques. Measurements of electrical and thermal transport properties of selected semiconductor materials prepared in accordance with the present invention, demonstrated high Hall mobilities and good Seebeck coefficients. These materials have low thermal conductivity and relatively low electrical resistivity, and are good candidates for low temperature thermoelectric applications.

  8. Prediction and Design of Materials from Crystal Structures to Nanocrystal Morphology and Assembly

    NASA Astrophysics Data System (ADS)

    Hennig, Richard

    2012-02-01

    Predictions of structure formation by computational methods have the potential to accelerate materials discovery and design. Here we present two computational approaches for the prediction of crystal structures and the morphology of nanoparticles. Many materials properties are controlled by composition and crystal structure. We show that evolutionary algorithms coupled to ab-initio relaxations can accurately predict the crystal structure and composition of compounds without any prior information about the system. We will discuss results for various systems including the prediction of unexpected quasi-1D and 2D electronic structures in Li-Be compounds under pressure [1] and of the crystal structure of the superconducting high-pressure phase of Eu [2]. The self-assembly of nanocrystals into mesoscale superlattices provides a path to the design of materials with tunable electronic, physical and chemical properties for various applications. The self-assembly is controlled by the nanocrystal shape and by ligand-mediated interactions between them. To understand this, it is necessary to know the effect of the ligands on the surface energies (which tune the nanocrystal shape), as well as the relative coverage of the different facets (which control the interactions). Density functional calculations for the binding energy of oleic acid-based ligands on PbSe nanocrystals determine the surface energies as a function of ligand coverage. The Wulff construction predicts the thermodynamic equilibrium shape of the PbSe nanocrystals as a function of the ligand coverage. We show that the different ligand binding energies on the 100 and 111 facets results in different ligand coverages on the facets and predict a transition in the equilibrium shape from octahedral to cubic when increasing the ligand concentration during synthesis. Our results furthermore suggest that the experimentally observed transformation of the nanocrystal superlattice structure from fcc to bcc is caused by the

  9. Correlation between hierarchical structure of crystal networks and macroscopic performance of mesoscopic soft materials and engineering principles.

    PubMed

    Lin, Naibo; Liu, Xiang Yang

    2015-11-01

    This review examines how the concepts and ideas of crystallization can be extended further and applied to the field of mesoscopic soft materials. It concerns the structural characteristics vs. the macroscopic performance, and the formation mechanism of crystal networks. Although this subject can be discussed in a broad sense across the area of mesoscopic soft materials, our main focus is on supramolecular materials, spider and silkworm silks, and biominerals. First, the occurrence of a hierarchical structure, i.e. crystal network and domain network structures, will facilitate the formation kinetics of mesoscopic phases and boost up the macroscopic performance of materials in some cases (i.e. spider silk fibres). Second, the structure and performance of materials can be correlated in some way by the four factors: topology, correlation length, symmetry/ordering, and strength of association of crystal networks. Moreover, four different kinetic paths of crystal network formation are identified, namely, one-step process of assembly, two-step process of assembly, mixed mode of assembly and foreign molecule mediated assembly. Based on the basic mechanisms of crystal nucleation and growth, the formation of crystal networks, such as crystallographic mismatch (or noncrystallographic) branching (tip branching and fibre side branching) and fibre/polymeric side merging, are reviewed. This facilitates the rational design and construction of crystal networks in supramolecular materials. In this context, the (re-)construction of a hierarchical crystal network structure can be implemented by thermal, precipitate, chemical, and sonication stimuli. As another important class of soft materials, the unusual mechanical performance of spider and silkworm silk fibres are reviewed in comparison with the regenerated silk protein derivatives. It follows that the considerably larger breaking stress and unusual breaking strain of spider silk fibres vs. silkworm silk fibres can be interpreted

  10. Structuring of material parameters in lithium niobate crystals with low-mass, high-energy ion radiation

    NASA Astrophysics Data System (ADS)

    Peithmann, K.; Eversheim, P.-D.; Goetze, J.; Haaks, M.; Hattermann, H.; Haubrich, S.; Hinterberger, F.; Jentjens, L.; Mader, W.; Raeth, N. L.; Schmid, H.; Zamani-Meymian, M.-R.; Maier, K.

    2011-10-01

    Ferroelectric lithium niobate crystals offer a great potential for applications in modern optics. To provide powerful optical components, tailoring of key material parameters, especially of the refractive index n and the ferroelectric domain landscape, is required. Irradiation of lithium niobate crystals with accelerated ions causes strong structured modifications in the material. The effects induced by low-mass, high-energy ions (such as 3He with 41 MeV, which are not implanted, but transmit through the entire crystal volume) are reviewed. Irradiation yields large changes of the refractive index Δn, improved domain engineering capability within the material along the ion track, and waveguiding structures. The periodic modification of Δn as well as the formation of periodically poled lithium niobate (PPLN) (supported by radiation damage) is described. Two-step knock-on displacement processes, 3He→Nb and 3He→O causing thermal spikes, are identified as origin for the material modifications.

  11. Crystallographic approaches for the investigation of molecular materials: structure property relationships and reverse crystal engineering.

    PubMed

    Macchi, Piero

    2014-01-01

    This article discusses the connection between crystallography and material science. It sheds light on some of the research opportunities that are currently available and it critically reviews the directions taken by the scientific community in the field of crystal engineering. The focus is on materials formed by the assembly of organic and organometallic molecular building blocks. PMID:24801694

  12. Efficient crystallization induced emissive materials based on a simple push-pull molecular structure.

    PubMed

    Cariati, Elena; Lanzeni, Valentina; Tordin, Elisa; Ugo, Renato; Botta, Chiara; Schieroni, Alberto Giacometti; Sironi, Angelo; Pasini, Dario

    2011-10-28

    Solid state luminescent materials are the subject of ever growing interest both from a scientific and a technological point of view. Aggregation caused quenching (ACQ) processes however represent an obstacle to the development of most luminogens in the condensed phase. This is why particularly fascinating are those materials showing higher emission intensity in the solid state than in solution. Here we report on three 4-dialkylamino-2-benzylidene malonic acid dialkyl esters, very simple push-pull molecules, which are hardly emissive in solution and in the amorphous phase but become good emitters in the crystalline phase according to what has been indicated as crystallization induced emission (CIE). Thanks to combined emission and NMR spectroscopies at different temperatures on the prototype compound 4-dimethylamino-2-benzylidene malonic acid dimethyl ester in solution, we give full evidence that a restricted intramolecular rotation (RIR) phenomenon, in particular the hindered rotation around the aryl main axis of the compound, is at the origin of this behaviour. In addition, solid state photophysical and X-ray diffraction structural characterization allow us to identify J-dimeric interactions as responsible for the particularly intense emission of two of the three compounds. Moreover, by exploiting the compounds' acidochromic properties, applications in sensors and optoelectronics are envisaged. PMID:21915408

  13. Crystal Structure Prediction and its Application in Earth and Materials Sciences

    NASA Astrophysics Data System (ADS)

    Zhu, Qiang

    First of all, we describe how to predict crystal structure by evolutionary approach, and extend this method to study the packing of organic molecules, by our specially designed constrained evolutionary algorithm. The main feature of this new approach is that each unit or molecule is treated as a whole body, which drastically reduces the search space and improves the efficiency. The improved method is possibly to be applied in the fields of (1) high pressure phase of simple molecules (H2O, NH3, CH4, etc); (2) pharmaceutical molecules (glycine, aspirin, etc); (3) complex inorganic crystals containing cluster or molecular unit, (Mg(BH4)2, Ca(BH4)2, etc). One application of the constrained evolutionary algorithm is given by the study of (Mg(BH4)2, which is a promising materials for hydrogen storage. Our prediction does not only reproduce the previous work on Mg(BH4)2 at ambient condition, but also yields two new tetragonal structures at high pressure, with space groups P4 and I41/acd are predicted to be lower in enthalpy, by 15.4 kJ/mol and 21.2 kJ/mol, respectively, than the earlier proposed P42nm phase. We have simulated X-ray diffraction spectra, lattice dynamics, and equations of state of these phases. The density, volume contraction, bulk modulus, and the simulated XRD patterns of P4 and I41/acd structures are in excellent agreement with the experimental results. Two kinds of oxides (Xe-O and Mg-O) have been studied under megabar pressures. For XeO, we predict the existence of thermodynamically stable Xe-O compounds at high pressures (XeO, XeO2 and XeO3 become stable at pressures of 83, 102 and 114 GPa, respectively). For Mg-O, our calculations find that two extraordinary compounds MgO2 and Mg3O 2 become thermodynamically stable at 116 GPa and 500 GPa, respectively. Our calculations indicate large charge transfer in these oxides for both systems, suggesting that large electronegativity difference and pressure are the key factors favouring their formations. We also

  14. Structural, thermal and optical characterization of an organic NLO material--benzaldehyde thiosemicarbazone monohydrate single crystals.

    PubMed

    Santhakumari, R; Ramamurthi, K

    2011-02-01

    Single crystals of the organic NLO material, benzaldehyde thiosemicarbazone (BTSC) monohydrate, were grown by slow evaporation method. Solubility of BTSC monohydrate was determined in ethanol at different temperatures. The grown crystals were characterized by single crystal X-ray diffraction analysis to determine the cell parameters and by FT-IR technique to study the presence of the functional groups. Thermogravimetric and differential thermal analyses reveal the thermal stability of the crystal. UV-vis-NIR spectrum shows excellent transmission in the region of 200-1100 nm. Theoretical calculations were carried out to determine the linear optical constants such as extinction coefficient and refractive index. Further the optical nonlinearities of BTSC have been investigated by Z-scan technique with He-Ne laser radiation of wavelength 632.8 nm. Mechanical properties of the grown crystal were studied using Vickers microhardness tester. Second harmonic generation efficiency of the powdered BTSC monohydrate was tested using Nd:YAG laser and it is found to be ∼5.3 times that of potassium dihydrogen orthophosphate. PMID:21186136

  15. Nondestructive optical testing of the materials surface structure based on liquid crystals

    NASA Astrophysics Data System (ADS)

    Tomilin, M. G.; Stafeev, S. K.

    2011-08-01

    Thin layers of nematic liquid crystals (NLCs) may be used as recording media for visualizing structural and microrelief defects, distribution of low power physical fields and modifications of the surface. NLCs are more sensitive in comparison with cholesteric and smectic LCs having super molecular structures. The detecting properties of NLCs are based on local layers deformation, induced by surface fields and observed in polarizing microscope. The structural surface defects or physical field's distribution are dramatically change the distribution of surface tension. Surface defects recording becomes possible if NLC deformed structure is illuminated in transparent or reflective modes and observed in optical polarizing microscope and appearing image is compared with background structure. In this case one observes not the real defect but the local deformation in NLCs. The theory was developed to find out the real size of defects. The resolution of NLC layer is more than 2000 lines/mm. The fields of NLC application are solid crystals symmetry, minerals, metals, semiconductors, polymers and glasses structure inhomogeneities and optical coatings defects detecting. The efficiency of NLC method in biophotonics is illustrated by objective detecting cancer tissues character and visualizing the interaction traces of grippe viruses with antibodies. NLCs may detect solvent components structure in tea, wine and perfume giving unique information of their structure. It presents diagnostic information alternative to dyes and fluorescence methods. For the first time the structures of some juices and beverages are visualized to illustrate the unique possibilities of NLCs.

  16. Crystal structure of MCM-70: A microporous material with high framework density.

    PubMed

    Dorset, Douglas L; Kennedy, Gordon J

    2005-07-28

    The crystal structure of the borosilicate MCM-70 (siliceous framework formula Si12O24) was determined from synchrotron powder diffraction data with the program FOCUS. The framework crystallizes in space group Pmn2(1), where a = 13.663, b = 4.779, c = 8.723 A, and forms 1D ellipsoidal 10-ring channels with the following dimensions: 5.0 x 3.1 A. Rietveld refinement of the model against synchrotron powder data from solvated material gives Rwp = 0.15, R(F2) = 0.11. In addition to the four tetrahedral sites and seven framework oxygens, one potassium position is found during this refinement. Because of the unreasonable geometry of five putative extraframework oxygen sites, another synchrotron pattern was obtained from a dehydrated specimen. A refinement in space group P1n1 (removing the mirror operation of Pmn2(1)), where a = 13.670, b = 4.781, c = 8.687 A, and beta = 90.24 degrees , verified that the previous framework geometry is preserved as well as the potassium position. One extraframework oxygen was located that would yield a reasonable K-O distance. The existence of potassium is verified by electron energy dispersive spectroscopic measurements as well as quantitative elemental analysis. (There are approximately 2.35 K sites per 12 Si in the unit cell.) It is likely that the constricted channels occlude KOH. 11B and 29Si MAS NMR measurements indicate a framework SiO2/B2O3 of approximately 40:1, which is consistent with a wavelength dispersive spectroscopic measurement. The silicate framework density is 2.10 gm/cm3. The resulting framework density for T sites, 21.1, is unusually high for a zeolite, just below the value for paracelsian (21.4) or scapolite (21.8), each of which also has a smallest four-ring loop. The 1H --> 29Si CP MAS measurements suggest sample heterogeneity, that is, a portion of the sample that is strongly coupled to hydrogen and efficiently cross polarizes and another portion that does not. PMID:16852743

  17. Structural and optical properties of calcium neodymium hexaaluminates single crystals, potential laser materials

    NASA Astrophysics Data System (ADS)

    Alablanche, S.; Kahn-Harari, A.; Thery, J.; Viana, B.; Vivien, D.; Dexpert-Ghys, J.; Faucher, M.

    1992-05-01

    The structural and optical properties of calcium-neodymium hexaaluminates crystals Ca 1- xNd xMg x Al 12- xO 19 (labeled Ca 1- xNd x) with a magnetoplumbite (MP) structure are investigated. The floating zone method is used to grow single crystals in the composition range 0.1 ≤ x ≤ 0.7, although for high calcium content, the melting of the compounds is no longer congruent. The X-ray structural determination, optical absorption at 4 K, and ESR investigation agree in the localization of Nd 3+ at the regular large cations site of the MP structure with axial ( D3 h) symmetry. A set of crystal field and free ion parameters which fits the absorption spectrum of Nd 3+ in this site is calculated. When x increases, Nd 3+ ions tend to occupy also a second site with lower symmetry. Moreover some anomalous behavior observed in the absorption and ESR spectra at high neodymium concentration may be related to Nd 3+-Nd 3+ ion pairing. Fluorescence intensity and lifetime measurements as a function of the x value are reported. There is evidence of strong cross-relaxation between neighboring neodymium ions for high x values. The results obtained for the Ca 1- xNd x compounds can be extended to other series in which Nd 3+ is replaced by another lanthanide ion. Preliminary investigations have been performed with Pr 3+ and are also reported.

  18. Thermoelectric material including a multiple transition metal-doped type I clathrate crystal structure

    DOEpatents

    Yang, Jihui; Shi, Xun; Bai, Shengqiang; Zhang, Wenqing; Chen, Lidong; Yang, Jiong

    2012-01-17

    A thermoelectric material includes a multiple transition metal-doped type I clathrate crystal structure having the formula A.sub.8TM.sub.y.sub.1.sup.1TM.sub.y.sub.2.sup.2 . . . TM.sub.y.sub.n.sup.nM.sub.zX.sub.46-y.sub.1.sub.-y.sub.2.sub.- . . . -y.sub.n.sub.-z. In the formula, A is selected from the group consisting of barium, strontium, and europium; X is selected from the group consisting of silicon, germanium, and tin; M is selected from the group consisting of aluminum, gallium, and indium; TM.sup.1, TM.sup.2, and TM.sup.n are independently selected from the group consisting of 3d, 4d, and 5d transition metals; and y.sub.1, y.sub.2, y.sub.n and Z are actual compositions of TM.sup.1, TM.sup.2, TM.sup.n, and M, respectively. The actual compositions are based upon nominal compositions derived from the following equation: z=8q.sub.A-|.DELTA.q.sub.1|y.sub.1-|.DELTA.q.sub.2|y.sub.2- . . . -|.DELTA.q.sub.n|y.sub.n, wherein q.sub.A is a charge state of A, and wherein .DELTA.q.sub.1, .DELTA.q.sub.2, .DELTA.q.sub.n are, respectively, the nominal charge state of the first, second, and n-th TM.

  19. Photonic Crystal Laser Accelerator Structures

    SciTech Connect

    Cowan, Benjamin M

    2003-05-21

    Photonic crystals have great potential for use as laser-driven accelerator structures. A photonic crystal is a dielectric structure arranged in a periodic geometry. Like a crystalline solid with its electronic band structure, the modes of a photonic crystal lie in a set of allowed photonic bands. Similarly, it is possible for a photonic crystal to exhibit one or more photonic band gaps, with frequencies in the gap unable to propagate in the crystal. Thus photonic crystals can confine an optical mode in an all-dielectric structure, eliminating the need for metals and their characteristic losses at optical frequencies. We discuss several geometries of photonic crystal accelerator structures. Photonic crystal fibers (PCFs) are optical fibers which can confine a speed-of-light optical mode in vacuum. Planar structures, both two- and three-dimensional, can also confine such a mode, and have the additional advantage that they can be manufactured using common microfabrication techniques such as those used for integrated circuits. This allows for a variety of possible materials, so that dielectrics with desirable optical and radiation-hardness properties can be chosen. We discuss examples of simulated photonic crystal structures to demonstrate the scaling laws and trade-offs involved, and touch on potential fabrication processes.

  20. Advancements in the quantification of the crystal structure of ZnS materials produced in variable gravity

    NASA Astrophysics Data System (ADS)

    Castillo, Martin; Hales, Matthew; Lynn, David; Steinberg, Theodore

    SHS allows for the rapid creation of difficult to produce intermetallic materials, biomedical materials, and cermet materials by taking advantage of internal chemical energy present in the mixture. This manufacturing method utilities a rapid exothermic process involving high energy and nolinearity coupled with a high cooling rate to produce materials formed outside of normal equilibrium boundaries thus possessing unique properties. The elimination of gravity during this process allows capillary forces to dominate mixing of the reactants which results in a superior and enhanced homogeneity in the product materials formed The self-propagating high temperature synthesis (SHS) of ZnS type materials have been previously conducted in reduced gravity and normal gravity. It has been claimed in literature that a near perfect phases of ZnS wurtzite was produced. Although, the SHS of this material is possible at high pressures, there has been no quantitative information on the actual crystal structures and lattice parameters that were produced in this work. Utilizing this process with ZnS doped with Cu, Mn, or rare earth metals such as Eu and Pr leads to electroluminescence properties, thus making this an attractive electroluminescent material. The work described here will revisit the synthesis of ZnS via high pressure SHS and will re-examine the work performed in both normal gravity and in reduced gravity within the Queensland University of Technology Drop Tower Facility. Quantifications in the lattice parameters, crystal structures, and phases produced are presented to further explore the unique structure-property performance relationships produced from the SHS of ZnS materials.

  1. Crystal structure and mechanical properties of spark plasma sintered Cu2Se: An efficient photovoltaic and thermoelectric material

    NASA Astrophysics Data System (ADS)

    Tyagi, Kriti; Gahtori, Bhasker; Bathula, Sivaiah; Jayasimhadri, M.; Sharma, Sakshi; Singh, Niraj Kumar; Haranath, D.; Srivastava, A. K.; Dhar, Ajay

    2015-04-01

    Copper selenide (Cu2Se) based materials are currently being investigated globally for efficient photovoltaic and thermoelectric (TE) device applications. Despite having enormous device potential its crystal structure and mechanical properties are still not fully explored owing to its complex behavior. Stereographic projection is one of such useful tools to estimate the crystallography of the material conclusively. In the current study, the crystal structure of α and β-phases of Cu2Se was determined by its stereographic projections in reciprocal space. Further, mechanical properties of Cu2Se are highly important to avoid catastrophic failure and ensure longevity of the TE devices made out of these materials. Cu2Se exhibited the compressive strength of ~45 MPa with ~3% of plastic strain and a fracture toughness value of ~2±0.02 MPa√m, the latter being significantly higher than that of the other known TE materials. Finally, thermal shock resistance, which is one of the crucial parameters for the stability and longevity of the device applications, was calculated to be ~281±12 W m-1. Superior mechanical properties coupled with highly reported thermoelectric behavior makes Cu2Se as a potential candidate for green energy generation.

  2. Low dielectric electromagnetic absorbing material in 18-40 GHz using large scale photonic crystal structures

    NASA Astrophysics Data System (ADS)

    Narita, T.; Matsumura, K.; Kagawa, Y.

    2007-02-01

    The interaction behavior between a monolithic low dielectric block with unidirectionally aligned through holes and an electromagnetic wave at a frequency range from 18to40GHz has been studied. Hexagonally aligned through holes, whose diameters are 8.0, 9.0, and 10.0mm, are introduced to a polymethylmethacrylate block. The electromagnetic wave reflection and transmission spectra perpendicular to the hole axis show a unique structure dependence, which is related to the diameter of the hole and its arrangement. A large decrease in the reflectance and transmittance appears in the spectra, which originates from the interference effect between the electromagnetic wave and material. It is concluded that the material has a potential for controlling the electromagnetic wave at a tailored target frequency and is expected to be usable as monolithic low dielectric electromagnetic wave absorbing material.

  3. Computerized crystal-chemical classification of silicates and related materials with CRYSTANA and formula notation for classified structures

    NASA Astrophysics Data System (ADS)

    Klein, Hans-Joachim; Liebau, Friedrich

    2008-09-01

    The computer program CRYSTANA is described which implements a method for the crystal-chemical classification of silicates and related materials. This method is mainly based upon the topological structure of the connected units of a compound and can be applied when the units are built from tetrahedra as coordination polyhedra. The classification parameters and the rules which have to be applied for their determination are summarized and a formalization of the method is provided based upon a finite graph representation of the units. A description of how CRYSTANA can be used and which kind of output it produces is included. From this output crystal-chemical formulas can be derived, which differ slightly from an existing notation in order to meet recommendations of the International Union of Crystallography.

  4. Crystal growth, structure and characterizations of a new semiorganic nonlinear optical material-{beta}-Alanine zinc chloride

    SciTech Connect

    Anbuchezhiyan, M.; Ponnusamy, S.; Muthamizhchelvan, C.; Sivakumar, K.

    2010-08-15

    The title compound, {beta}-alanine zinc chloride-a new semiorganic nonlinear optical crystal was grown by slow evaporation technique. Single crystals of {beta}-alanine zinc chloride have been subjected to X-ray diffraction analysis to determine the crystal structure. The powder X-ray diffractogram of the crystal has also been recorded. The amount of carbon, nitrogen and hydrogen in the crystals was also estimated. Fourier Transform Infrared and Raman spectral measurements have been carried out on the grown crystals in order to identify the functional groups. The presence of hydrogen and carbon in the {beta}-alanine zinc chloride was confirmed by using proton and carbon nuclear magnetic resonance spectral analyses. The percentage of zinc in the crystal was determined by atomic absorption spectroscopy. Optical behavior such as ultraviolet-vis-near infrared transmittance spectrum and second harmonic generation has been investigated. The mechanical strength and thermal behavior of the grown crystal have been analyzed.

  5. Multiscale Modeling of Structurally-Graded Materials Using Discrete Dislocation Plasticity Models and Continuum Crystal Plasticity Models

    NASA Technical Reports Server (NTRS)

    Saether, Erik; Hochhalter, Jacob D.; Glaessgen, Edward H.

    2012-01-01

    A multiscale modeling methodology that combines the predictive capability of discrete dislocation plasticity and the computational efficiency of continuum crystal plasticity is developed. Single crystal configurations of different grain sizes modeled with periodic boundary conditions are analyzed using discrete dislocation plasticity (DD) to obtain grain size-dependent stress-strain predictions. These relationships are mapped into crystal plasticity parameters to develop a multiscale DD/CP model for continuum level simulations. A polycrystal model of a structurally-graded microstructure is developed, analyzed and used as a benchmark for comparison between the multiscale DD/CP model and the DD predictions. The multiscale DD/CP model follows the DD predictions closely up to an initial peak stress and then follows a strain hardening path that is parallel but somewhat offset from the DD predictions. The difference is believed to be from a combination of the strain rate in the DD simulation and the inability of the DD/CP model to represent non-monotonic material response.

  6. Materials and structures

    NASA Technical Reports Server (NTRS)

    Saito, Theodore T.; Langenbeck, Sharon L.; Al-Jamily, Ghanim; Arnold, Joe; Barbee, Troy; Coulter, Dan; Dolgin, Ben; Fichter, Buck; George, Patricia; Gorenstein, Paul

    1992-01-01

    Materials and structures technology covers a wide range of technical areas. Some of the most pertinent issues for the Astrotech 21 missions include dimensionally stable structural materials, advanced composites, dielectric coatings, optical metallic coatings for low scattered light applications, low scattered light surfaces, deployable and inflatable structures (including optical), support structures in 0-g and 1-g environments, cryogenic optics, optical blacks, contamination hardened surfaces, radiation hardened glasses and crystals, mono-metallic telescopes and instruments, and materials characterization. Some specific examples include low coefficients of thermal expansion (CTE) structures (0.01 ppm/K), lightweight thermally stable mirror materials, thermally stable optical assemblies, high reliability/accuracy (1 micron) deployable structures, and characterization of nanometer level behavior of materials/structures for interferometry concepts. Large filled-aperture concepts will require materials with CTE's of 10(exp 9) at 80 K, anti-contamination coatings, deployable and erectable structures, composite materials with CTE's less than 0.01 ppm/K and thermal hysteresis, 0.001 ppm/K. Gravitational detection systems such as LAGOS will require rigid/deployable structures, dimensionally stable components, lightweight materials with low conductivity, and high stability optics. The Materials and Structures panel addressed these issues and the relevance of the Astrotech 21 mission requirements by dividing materials and structures technology into five categories. These categories, the necessary development, and applicable mission/program development phasing are summarized. For each of these areas, technology assessments were made and development plans were defined.

  7. Crystal structure of the high-energy-density material guanylurea dipicryl­amide

    PubMed Central

    Deblitz, Raik; Hrib, Cristian G.; Hilfert, Liane; Edelmann, Frank T.

    2014-01-01

    The title compound, 1-carbamoylguanidinium bis­(2,4,6-tri­nitro­phen­yl)amide [H2NC(=O)NHC(NH2)2]+[N{C6H2(NO2)3-2,4,6}2]− (= guanylurea dipicryl­amide), was prepared as dark-red block-like crystals in 70% yield by salt-metathesis reaction between guanylurea sulfate and sodium dipicryl­amide. In the solid state, the new compound builds up an array of mutually linked guanylurea cations and dipicryl­amide anions. The crystal packing is dominated by an extensive network of N—H⋯O hydrogen bonds, resulting in a high density of 1.795 Mg m−3, which makes the title compound a potential secondary explosive. PMID:25249869

  8. Structure, crystal growth, optical and mechanical studies of poly bis (thiourea) silver (I) nitrate single crystal: A new semi organic NLO material

    NASA Astrophysics Data System (ADS)

    Sivakumar, N.; Kanagathara, N.; Varghese, B.; Bhagavannarayana, G.; Gunasekaran, S.; Anbalagan, G.

    2014-01-01

    A new semi organic non linear optical polymeric crystal, bis (thiourea) silver (I) nitrate (TuAgN) with dimension 8 × 7 × 1.5 mm3 has been successfully grown from aqueous solution by slow evaporation solution technique. Single crystal X-ray diffraction study reveals that the crystal belongs to orthorhombic system with non centrosymmetric space group C2221. The crystalline perfection of the crystal was analyzed by high resolution X-ray diffraction (HRXRD) rocking curve measurements. Functional groups present in the crystal were analyzed qualitatively by infrared and Confocal Raman spectral analysis. Effects due to coordination of thiourea with metal ions were also discussed. Optical absorption study on TuAgN crystal shows the minimum absorption in the entire UV-Vis region and the lower cut off wavelength of TuAgN is found to be 318 nm. Thermal analysis shows that the material is thermally stable up to 180 °C. The mechanical strength and its parameters of the grown crystal were estimated by Vicker's microhardness test. The second harmonic generation (SHG) efficiency of the crystal was measured by Kurtz's powder technique infers that the crystal has nonlinear optical (NLO) efficiency 0.85 times that of KDP.

  9. Synthesis, growth, structural, spectral, thermal, chemical etching, linear and nonlinear optical and mechanical studies of an organic single crystal 4-chloro 4-nitrostilbene (CONS): A potential NLO material

    NASA Astrophysics Data System (ADS)

    Dinakaran, Paul M.; Kalainathan, S.

    2013-07-01

    4-Chloro 4-nitrostilbene (CONS) a new organic nonlinear optical material has been synthesized. Employing slow evaporation method, good optical quality single crystals (dimensions up to 6 × 2 × 3 mm3) have been grown using ethyl methyl ketone (EMK) as a solvent. The grown crystals have been subjected to various characterizations such as single crystal X-ray diffraction, powder XRD, Fourier Transform Infrared spectroscopy (FTIR), proton NMR, solid UV absorption, SHG studies. Single crystal X-ray diffraction reveals that the crystal system belongs to monoclinic with noncentrosymmetric space group P21. The UV-Vis absorption spectrum has been recorded and found that the cut off wavelength is 380 nm. Functional groups and the structure of the title compound have been confirmed by FTIR and 1H NMR spectroscopic analyses respectively. Molecular mass of the CONS confirmed by the high resolution mass spectral analysis .The thermal behavior of the grown crystal has been studied by TG/DTA analysis and it shows the melting point is at 188.66 °C. Dislocations and growth pattern present in the grown crystal revealed by the etching study. The mechanical strength of the CONS crystal has been studied by Vicker's hardness measurement. The SHG efficiency of the grown crystal has been determined by Kurtz and Perry powder test which revealed that the CONS crystal (327 mV) has 15 times greater efficiency than that of KDP (21.7 mV).

  10. Crystal and electronic structures of nitridophosphate compounds as cathode materials for Na-ion batteries

    NASA Astrophysics Data System (ADS)

    Debbichi, M.; Lebègue, S.

    2015-08-01

    Using density-functional theory, we have studied the electronic and magnetic properties of two promising compounds that can be used as cathode materials, namely, Na2Fe2P3O9N and Na3TiP3O9N . When Na is extracted, we found the volume change to be quite small, with values of ˜-0.6 % for Na3TiP3O9N and -5 % for Na2Fe2P3O9N . Our calculated voltages with the Hubbard-type correction (GGA+U) approximation are 2.93 V for Na3TiP3O9N /Na2TiP3O9N and 2.68 V for Na2Fe2P3O9N /NaFe2P3O9N , in good agreement with the experimental data. Our results confirm that these compounds are very promising for rechargeable Na-ion batteries.

  11. Station for X-ray structural analysis of materials and single crystals (including nanocrystals) on a synchrotron radiation beam from the wiggler at the Siberia-2 storage ring

    SciTech Connect

    Kheiker, D. M. Kovalchuk, M. V.; Korchuganov, V. N.; Shilin, Yu. N.; Shishkov, V. A.; Sulyanov, S. N.; Dorovatovskii, P. V.; Rubinsky, S. V.; Rusakov, A. A.

    2007-11-15

    The design of the station for structural analysis of polycrystalline materials and single crystals (including nanoobjects and macromolecular crystals) on a synchrotron radiation beam from the superconducting wiggler of the Siberia-2 storage ring is described. The wiggler is constructed at the Budker Institute of Nuclear Physics of the Siberian Division of the Russian Academy of Sciences. The X-ray optical scheme of the station involves a (1, -1) double-crystal monochromator with a fixed position of the monochromatic beam and a sagittal bending of the second crystal, segmented mirrors bent by piezoelectric motors, and a (2{theta}, {omega}, {phi}) three-circle goniometer with a fixed tilt angle. Almost all devices of the station are designed and fabricated at the Shubnikov Institute of Crystallography of the Russian Academy of Sciences. The Bruker APEX11 two-dimensional CCD detector will serve as a detector in the station.

  12. Materials discovery through crystal growth

    NASA Astrophysics Data System (ADS)

    zur Loye, Hans-Conrad

    2016-04-01

    The discovery of new materials and associated desirable properties has been a driving force behind chemical innovation for centuries. When we look at some of the many recent technological advances, and how widespread and significant their impact has been, we appreciate how much they have relied on new materials. The increase in hard drive storage capacity due to new giant magneto-resistive materials, the ever-shrinking cell phone due to improved microwave dielectric materials, the enhancement in lithium battery storage capacity due to new intercalation materials, or the improved capacitor due to new ferroelectric materials are all excellent examples. How were these materials discovered? While there is no single answer, in all cases there was a First-Material, the archetype in which the phenomenon was first observed, the one that led to further investigations and the subsequent preparation of improved 2nd or 3rd generation materials. It is this First-Material, the archetype, that was discovered - often via crystal growth.

  13. Ca10Li(VO4)7:Nd3+, a promising laser material: growth, structure and spectral characteristics of a Czochralski-grown single crystal

    NASA Astrophysics Data System (ADS)

    Kosmyna, M. B.; Nazarenko, B. P.; Puzikov, V. M.; Shekhovtsov, A. N.; Paszkowicz, W.; Behrooz, A.; Romanowski, P.; Yasukevich, A. S.; Kuleshov, N. V.; Demesh, M. P.; Wierzchowski, W.; Wieteska, K.; Paulmann, C.

    2016-07-01

    Pure and Nd-doped Ca10Li(VO4)7 single crystals were grown by the Czochralski method. The structure of Ca10Li(VO4)7 single crystal was refined starting from a model of Ca10K(VO4)7 using the powder diffraction data collected at a laboratory high-resolution diffractometer. The defect structure of the single crystal was studied with the use of both, high-resolution diffraction using a laboratory instrument and X-ray topographic techniques employing synchrotron radiation at the Hasylab laboratory (Hamburg). Polarized absorption and luminescence spectra of Nd-doped Ca10Li(VO4)7 crystal were investigated in details. The laser oscillation was obtained under flash lamp pumping and the slope efficiency of 0.87% was achieved in the free-running mode. Preliminary examination of lasing properties points that Ca10Li(VO4)7:Nd crystal can be a highly efficient solid state laser medium. Crystals of this kind are expected to be suitable for application as efficient non-linear optics materials.

  14. Pattern information extraction from crystal structures

    NASA Astrophysics Data System (ADS)

    Okuyan, Erhan; Güdükbay, Uğur; Gülseren, Oğuz

    2007-04-01

    Determining the crystal structure parameters of a material is an important issue in crystallography and material science. Knowing the crystal structure parameters helps in understanding the physical behavior of material. It can be difficult to obtain crystal parameters for complex structures, particularly those materials that show local symmetry as well as global symmetry. This work provides a tool that extracts crystal parameters such as primitive vectors, basis vectors and space groups from the atomic coordinates of crystal structures. A visualization tool for examining crystals is also provided. Accordingly, this work could help crystallographers, chemists and material scientists to analyze crystal structures efficiently. Program summaryTitle of program: BilKristal Catalogue identifier: ADYU_v1_0 Program summary URL:http://cpc.cs.qub.ac.uk/summaries/ADYU_v1_0 Program obtainable from: CPC Program Library, Queen's University of Belfast, N. Ireland Licensing provisions: None Programming language used: C, C++, Microsoft .NET Framework 1.1 and OpenGL Libraries Computer: Personal Computers with Windows operating system Operating system: Windows XP Professional RAM: 20-60 MB No. of lines in distributed program, including test data, etc.:899 779 No. of bytes in distributed program, including test date, etc.:9 271 521 Distribution format:tar.gz External routines/libraries: Microsoft .NET Framework 1.1. For visualization tool, graphics card driver should also support OpenGL Nature of problem: Determining crystal structure parameters of a material is a quite important issue in crystallography. Knowing the crystal structure parameters helps to understand physical behavior of material. For complex structures, particularly, for materials which also contain local symmetry as well as global symmetry, obtaining crystal parameters can be quite hard. Solution method: The tool extracts crystal parameters such as primitive vectors, basis vectors and identify the space group from

  15. Characterization of pore and crystal structure of synthesized LiBOB with varying quality of raw materials as electrolyte for lithium-ion battery

    NASA Astrophysics Data System (ADS)

    Lestariningsih, Titik; Ratri, Christin Rina; Wigayati, Etty Marty; Sabrina, Qolby

    2016-02-01

    Characterization of pore structure and crystal structure of the LiB(C2O4)2H2O or LIBOB compound has been performed in this study. These recent years, research regarding LiBOB electrolyte salt have been performed using analytical-grade raw materials, therefore this research was aimed to synthesized LiBOB electrolyte salt using the cheaper and abundant technical-grade raw materials. Lithium hydroxide (LiOH), oxalic acid dihydrate (H2C2O4.2H2O), and boric acid (H3BO3) both in technical-grade and analytical-grade quality were used as raw materials for the synthesis of LiBOB. Crystal structure characterization results of synthesized LiBOB from both technical-grade and analytical-grade raw materials have shown the existence of LiBOB and LiBOB hydrate phase with orthorombic structure. These results were also confirmed by FT-IR analysis, which showed the functional groups of LiBOB compounds. SEM analysis results showed that synthesized LiBOB has spherical structure, while commercial LiBOB has cylindrical structure. Synthesized LiBOB has a similar pore size of commercial LiBOB, i.e. 19 nm (mesoporous material). Surface area of synthesized LiBOB from analytical-grade raw materials and technical-grade materials as well as commercial LIBOB were 88.556 m2/g, 41.524 m2/g, and 108.776 m2/g, respectively. EIS analysis results showed that synthesized LiBOB from technical-grade raw materials has lower conductivity than synthesized LiBOB from analytical-grade raw materials.

  16. Emergent molecular theory of initiation of detonation: the effect of molecular and crystal structure on thermal stability of high density energy materials

    NASA Astrophysics Data System (ADS)

    Kukla, Maija; Tsyshevsky, Roman; Sharia, Onise

    The sensitivity to detonation initiation of high density energy materials along with their performance are two most important criteria for choosing the best material for explosive formulations, booster engines, detonators, etc. After numerous experimental and theoretical attempts to develop a single parameter describing sensitivity of different classes of energetic materials, one concludes that the complexity of physical and chemical explosive properties cannot be trivialized. We report here the results of our theoretical and computational studies of thermal decomposition mechanisms and kinetics of five classes of EM: pentaerythritol tetranitrate (PETN), nitramine cyclotetramethylene-tetranitramine (HMX), diamino-dinitroethene (DADNE), bis-(nitrofurazano)-furoxane (BNFF) and benchmark triamino-trinitrobenzene (TATB). Our modeling reveals how the thermal stability depends on the molecular structure of the material and how the crystal structure may additionally hinder or catalyze decomposition reactions. We will also discuss an effect of crystalline defects on sensitivity and performance of materials.

  17. Inorganic Crystal Structure Database (ICSD)

    National Institute of Standards and Technology Data Gateway

    SRD 84 FIZ/NIST Inorganic Crystal Structure Database (ICSD) (PC database for purchase)   The Inorganic Crystal Structure Database (ICSD) is produced cooperatively by the Fachinformationszentrum Karlsruhe(FIZ) and the National Institute of Standards and Technology (NIST). The ICSD is a comprehensive collection of crystal structure data of inorganic compounds containing more than 140,000 entries and covering the literature from 1915 to the present.

  18. Ionic Liquid Crystals: Versatile Materials.

    PubMed

    Goossens, Karel; Lava, Kathleen; Bielawski, Christopher W; Binnemans, Koen

    2016-04-27

    This Review covers the recent developments (2005-2015) in the design, synthesis, characterization, and application of thermotropic ionic liquid crystals. It was designed to give a comprehensive overview of the "state-of-the-art" in the field. The discussion is focused on low molar mass and dendrimeric thermotropic ionic mesogens, as well as selected metal-containing compounds (metallomesogens), but some references to polymeric and/or lyotropic ionic liquid crystals and particularly to ionic liquids will also be provided. Although zwitterionic and mesoionic mesogens are also treated to some extent, emphasis will be directed toward liquid-crystalline materials consisting of organic cations and organic/inorganic anions that are not covalently bound but interact via electrostatic and other noncovalent interactions. PMID:27088310

  19. Demonstration of Crystal Structure.

    ERIC Educational Resources Information Center

    Neville, Joseph P.

    1985-01-01

    Describes an experiment where equal parts of copper and aluminum are heated then cooled to show extremely large crystals. Suggestions are given for changing the orientation of crystals by varying cooling rates. Students are more receptive to concepts of microstructure after seeing this experiment. (DH)

  20. Temperature Dependence of Crystal Structure and THz Absorption Spectra of Organic Nonlinear Optical Stilbazolium Material for High-Output THz-Wave Generation

    NASA Astrophysics Data System (ADS)

    Matsukawa, Takeshi; Hoshina, Hiromichi; Hoshikawa, Akinori; Otani, Chiko; Ishigaki, Toru

    2016-06-01

    A stilbazolium material comprising 4-dimethylamino- N'-methyl-4'-stilbazolium tosylate (DAST), which has a large nonlinear optical susceptibility, was studied for application in terahertz (THz)-wave generation. The temperature-dependent structure of the DAST crystal was measured by using powder X-ray diffraction from -100 to 200 °C, indicating a volume expansion of 4.6 %. The lattice constants show anisotropic thermal expansion. Also, the temperature dependence of THz absorption spectra was measured by terahertz time-domain spectroscopy (THz-TDS) in the temperature range varying from -80 to 88.1 °C. A strong absorption peak was found at around 1 THz, shifting slightly toward a lower frequency with increasing temperature. The temperature dependence of the THz spectra was compared with that of X-ray diffraction. The shifting of THz-vibrational frequencies of the DAST crystal suggests that the change in its lattice structure is temperature dependent.

  1. Semiorganic nonlinear optical material: Crystal growth, structure and optical properties of NaB(L-C{sub 4}H{sub 4}O{sub 5}){sub 2}

    SciTech Connect

    Huang, Hongwei; Yao, Wenjiao; He, Ying; Tian, Na; Chen, Chuangtian; Zhang, Yihe

    2013-09-01

    Graphical abstract: - Highlights: • Semiorganic NLO material NaB(L-C{sub 4}H{sub 4}O{sub 5}){sub 2} has been grown with sizes up to 8 × 5 × 2 mm{sup 3}. • It crystallizes in the noncentrosymmetric Monoclinic space group P2. • Thermal analysis demonstrated NaB(L-C{sub 4}H{sub 4}O{sub 5}){sub 2} are thermally stable up to 280. • NaB(L-C{sub 4}H{sub 4}O{sub 5}){sub 2} has an absorption edge about 220 nm in the UV region. • It exhibits a NLO efficiency of about two times that of KDP (KH{sub 2}PO{sub 4}) standard. - Abstract: Single crystal of the semiorganic NLO material NaB(L-C{sub 4}H{sub 4}O{sub 5}){sub 2} has been grown with sizes up to 8 × 5 × 2 mm{sup 3} by the slow evaporation method. The crystal structure of this compound was determined by single crystal X-ray diffraction. It crystallizes in the Monoclinic space group P2 with lattice parameters a = 5.4045(11) Å, b = 11.692(2) Å, c = 9.4773(19) Å and Z = 2. Thermal analysis demonstrated NaB(L-C{sub 4}H{sub 4}O{sub 5}){sub 2} are thermally stable up to 280 °C. NaB(L-C{sub 4}H{sub 4}O{sub 5}){sub 2} exhibits an absorption edge about 220 nm in the UV region. The powder second-harmonic generation (SHG) measurement performed on the ground crystal indicates that it has a NLO efficiency of about 2 times that of KDP (KH{sub 2}PO{sub 4}) standard. In addition, the origin of stronger SHG effect was discussed.

  2. Photonic crystals with active organic materials

    NASA Astrophysics Data System (ADS)

    Wu, Yeheng

    The concept of photonic crystals, which involves periodically arranged dielectrics that form a new type of material having novel photonic properties, was first proposed about two decades ago. Since then, a number of applications in photonic technology have been explored. Specifically, organic and hybrid photonic crystals are promising because of the unique advantages of the organic materials. A one-dimensional (1D) photonic crystal (multilayer) has high reflectance across a certain wavelength range. We report on studies of 1D multilayer polymer films that were fabricated using spin-coating, free film stacking, and co-extrusion techniques. For example, a stack fabricated by placing a laser dye-doped gain medium between two multilayer reflecting polymer films forms a micro-resonator laser or distributed Bragg laser. The resulting laser system is made entirely of plastic and is only several tens of micrometers in thickness. When the gain, a dye-doped medium, comprises one type of a two-type multilayer film, it results a laser exhibiting distributed feedback. At the edge of the photonic band, the group velocity becomes small and the density of photon states becomes high, which leads to laser emission. Such distributed feedback lasers were fabricated using the co-extrusion technique. The refractive indices and the photonic lattice determine the photonic band gap, which can be tuned by changing these parameters. Materials with Kerr nonlinearity exhibit a change in refractive index depending on the incident intensity of the light. To demonstrate such switching, electrochemical etching techniques on silicon wafers were used to form two-dimensional (2D) photonic crystals. By incorporating the nonlinear organic material into the 2D structure, we have made all-optical switches. The reflection of a beam from the 2D photonic crystal can be controlled by another beam because it induces a refractive index change in the active material by altering the reflection band. A mid

  3. Crystal structure determination of Efavirenz

    NASA Astrophysics Data System (ADS)

    Popeneciu, Horea; Tripon, Carmen; Borodi, Gheorghe; Pop, Mihaela Maria; Dumitru, Ristoiu

    2015-12-01

    Needle-shaped single crystals of the title compound, C14H9ClF3NO2, were obtained from a co-crystallization experiment of Efavirenz with maleic acid in a (1:1) ratio, using methanol as solvent. Crystal structure determination at room temperature revealed a significant anisotropy of the lattice expansion compared to the previously reported low-temperature structure. In both low- and room temperature structures the cyclopropylethynyl fragment in one of the asymmetric unit molecules is disordered. While at low-temperature only one C atom exhibits positional disorder, at room temperature the disorder is present for two C atoms of the cyclopropane ring.

  4. Generation of crystal structures using known crystal structures as analogues

    PubMed Central

    Cole, Jason C.; Groom, Colin R.; Read, Murray G.; Giangreco, Ilenia; McCabe, Patrick; Reilly, Anthony M.; Shields, Gregory P.

    2016-01-01

    This analysis attempts to answer the question of whether similar molecules crystallize in a similar manner. An analysis of structures in the Cambridge Structural Database shows that the answer is yes – sometimes they do, particularly for single-component structures. However, one does need to define what we mean by similar in both cases. Building on this observation we then demonstrate how this correlation between shape similarity and packing similarity can be used to generate potential lattices for molecules with no known crystal structure. Simple intermolecular interaction potentials can be used to minimize these potential lattices. Finally we discuss the many limitations of this approach. PMID:27484374

  5. Crystal chemistry and application development of uranyl extended structure and nanoscale materials and actinyl ion-substituted mineral phases

    NASA Astrophysics Data System (ADS)

    Wylie, Ernest M.

    The worldwide use of nuclear energy presents both significant advantages and challenges for society. Actinide research seeks to address these challenges and drive advancement in the fields of nuclear science and engineering. Here, key aspects of the fuel cycle are examined from both a fundamental and an applications-based perspective. Hydrothermal, ionothermal, room-temperature evaporation, and liquid diffusion synthesis techniques and single-crystal X-ray diffraction were used to study the structures of 18 uranyl compounds and six actinyl-doped mineral phases. These compounds represent a diverse group ranging from unique molecular clusters to novel and known extended structures isolated from aqueous and ionic liquid media. Ultrafiltration techniques were utilized to separate uranyl peroxide nanoclusters from complex aqueous solutions. Inductively coupled plasma optical emission spectroscopy and mass spectrometry were used to quantify elemental distributions in the feed and permeate solutions while Raman spectroscopy, small-angle X-ray scattering, and electrospray ionization mass spectrometry were used to define the characteristics of the cluster species across a range different solution conditions.

  6. Automating the application of smart materials for protein crystallization

    PubMed Central

    Khurshid, Sahir; Govada, Lata; EL-Sharif, Hazim F.; Reddy, Subrayal M.; Chayen, Naomi E.

    2015-01-01

    The fabrication and validation of the first semi-liquid nonprotein nucleating agent to be administered automatically to crystallization trials is reported. This research builds upon prior demonstration of the suitability of molecularly imprinted polymers (MIPs; known as ‘smart materials’) for inducing protein crystal growth. Modified MIPs of altered texture suitable for high-throughput trials are demonstrated to improve crystal quality and to increase the probability of success when screening for suitable crystallization conditions. The application of these materials is simple, time-efficient and will provide a potent tool for structural biologists embarking on crystallization trials. PMID:25760603

  7. Crystallization and functionality of inorganic materials

    SciTech Connect

    Xue, Dongfeng; Li, Keyan; Liu, Jun; Sun, Congting; Chen, Kunfeng

    2012-10-15

    In this article, we briefly summarized our recent work on the studies of crystallization and functionality of inorganic materials. On the basis of the chemical bonding theory of single crystal growth, we can quantitatively simulate Cu{sub 2}O crystallization processes in solution system. We also kinetically controlled Cu{sub 2}O crystallization process in the reduction solution route. Lithium ion battery and supercapacitor performances of some oxides such as Co{sub 3}O{sub 4} and MnO{sub 2} were shown to elucidate the important effect of crystallization on functionality of inorganic materials. This work encourages us to create novel functionalities through the study of crystallization of inorganic materials, which warrants more chances in the field of functional materials.

  8. Concerning inorganic crystal structure types.

    PubMed

    Bergerhoff; Berndt; Brandenburg; Degen

    1999-04-01

    All representatives of an inorganic crystal structure type can be found systematically in the new database SICS (Standardized Inorganic Crystal Structures). It is derived from the Inorganic Crystal Structure Database (ICSD) by selecting the best determination of each phase. In addition, each entry is given in a standardized description and complemented by searchable descriptors Delta, which give the difference between all structures of an isopointal set. Because of the large number of structures the full information on relationships present can only be found by means of the new database itself. Some examples are given here in printed form. The limitations and the possibilities of expansion of SICS in terms of the concept of 'structure types' are demonstrated. PMID:10927350

  9. Structural materials and components

    NASA Technical Reports Server (NTRS)

    Gagliani, John (Inventor); Lee, Raymond (Inventor)

    1982-01-01

    High density structural (blocking) materials composed of a polyimide filled with glass microballoons and methods for making such materials. Structural components such as panels which have integral edgings and/or other parts made of the high density materials.

  10. Crystal structure of triclopyr

    PubMed Central

    Cho, Seonghwa; Kim, Jineun; Jeon, Youngeun; Kim, Tae Ho

    2014-01-01

    In the title compound {systematic name: 2-[(3,5,6-tri­chloro­pyridin-2-yl)­oxy]acetic acid}, the herbicide triclopyr, C7H4Cl3NO3, the asymmetric unit comprises two independent mol­ecules in which the dihedral angles between the mean plane of the carb­oxy­lic acid group and the pyridyl ring plane are 79.3 (6) and 83.8 (5)°. In the crystal, pairs of inter­molecular O—H⋯O hydrogen bonds form dimers through an R 2 2(8) ring motif and are extended into chains along [100] by weak π–π inter­actions [ring centroid separations = 3.799 (4) and 3.810 (4) Å]. In addition, short inter­molecular Cl⋯Cl contacts [3.458 (2) Å] connect the chains, yielding a two-dimensional architecture extending parallel to (020). The crystal studied was found to be non-merohedrally twinned with the minor component being 0.175 (4). PMID:25309266

  11. Crystal structure of triclopyr.

    PubMed

    Cho, Seonghwa; Kim, Jineun; Jeon, Youngeun; Kim, Tae Ho

    2014-09-01

    In the title compound {systematic name: 2-[(3,5,6-tri-chloro-pyridin-2-yl)-oxy]acetic acid}, the herbicide triclopyr, C7H4Cl3NO3, the asymmetric unit comprises two independent mol-ecules in which the dihedral angles between the mean plane of the carb-oxy-lic acid group and the pyridyl ring plane are 79.3 (6) and 83.8 (5)°. In the crystal, pairs of inter-molecular O-H⋯O hydrogen bonds form dimers through an R 2 (2)(8) ring motif and are extended into chains along [100] by weak π-π inter-actions [ring centroid separations = 3.799 (4) and 3.810 (4) Å]. In addition, short inter-molecular Cl⋯Cl contacts [3.458 (2) Å] connect the chains, yielding a two-dimensional architecture extending parallel to (020). The crystal studied was found to be non-merohedrally twinned with the minor component being 0.175 (4). PMID:25309266

  12. CuLi2Sn and Cu2LiSn: Characterization by single crystal XRD and structural discussion towards new anode materials for Li-ion batteries

    NASA Astrophysics Data System (ADS)

    Fürtauer, Siegfried; Effenberger, Herta S.; Flandorfer, Hans

    2014-12-01

    The stannides CuLi2Sn (CSD-427095) and Cu2LiSn (CSD-427096) were synthesized by induction melting of the pure elements and annealing at 400 °C. The phases were reinvestigated by X-ray powder and single-crystal X-ray diffractometry. Within both crystal structures the ordered CuSn and Cu2Sn lattices form channels which host Cu and Li atoms at partly mixed occupied positions exhibiting extensive vacancies. For CuLi2Sn, the space group F-43m. was verified (structure type CuHg2Ti; a=6.295(2) Å; wR2(F²)=0.0355 for 78 unique reflections). The 4(c) and 4(d) positions are occupied by Cu atoms and Cu+Li atoms, respectively. For Cu2LiSn, the space group P63/mmc was confirmed (structure type InPt2Gd; a=4.3022(15) Å, c=7.618(3) Å; wR2(F²)=0.060 for 199 unique reflections). The Cu and Li atoms exhibit extensive disorder; they are distributed over the partly occupied positions 2(a), 2(b) and 4(e). Both phases seem to be interesting in terms of application of Cu-Sn alloys as anode materials for Li-ion batteries.

  13. CuLi2Sn and Cu2LiSn: Characterization by single crystal XRD and structural discussion towards new anode materials for Li-ion batteries

    PubMed Central

    Fürtauer, Siegfried; Effenberger, Herta S.; Flandorfer, Hans

    2014-01-01

    The stannides CuLi2Sn (CSD-427095) and Cu2LiSn (CSD-427096) were synthesized by induction melting of the pure elements and annealing at 400 °C. The phases were reinvestigated by X-ray powder and single-crystal X-ray diffractometry. Within both crystal structures the ordered CuSn and Cu2Sn lattices form channels which host Cu and Li atoms at partly mixed occupied positions exhibiting extensive vacancies. For CuLi2Sn, the space group F-43m. was verified (structure type CuHg2Ti; a=6.295(2) Å; wR2(F²)=0.0355 for 78 unique reflections). The 4(c) and 4(d) positions are occupied by Cu atoms and Cu+Li atoms, respectively. For Cu2LiSn, the space group P63/mmc was confirmed (structure type InPt2Gd; a=4.3022(15) Å, c=7.618(3) Å; wR2(F²)=0.060 for 199 unique reflections). The Cu and Li atoms exhibit extensive disorder; they are distributed over the partly occupied positions 2(a), 2(b) and 4(e). Both phases seem to be interesting in terms of application of Cu–Sn alloys as anode materials for Li-ion batteries. PMID:25473128

  14. Crystal structure determination of Efavirenz

    SciTech Connect

    Popeneciu, Horea Dumitru, Ristoiu; Tripon, Carmen Borodi, Gheorghe Pop, Mihaela Maria

    2015-12-23

    Needle-shaped single crystals of the title compound, C{sub 14}H{sub 9}ClF{sub 3}NO{sub 2}, were obtained from a co-crystallization experiment of Efavirenz with maleic acid in a (1:1) ratio, using methanol as solvent. Crystal structure determination at room temperature revealed a significant anisotropy of the lattice expansion compared to the previously reported low-temperature structure. In both low- and room temperature structures the cyclopropylethynyl fragment in one of the asymmetric unit molecules is disordered. While at low-temperature only one C atom exhibits positional disorder, at room temperature the disorder is present for two C atoms of the cyclopropane ring.

  15. Materials and structures

    NASA Technical Reports Server (NTRS)

    Venneri, Samuel L.

    1988-01-01

    Information on materials and structures for use in space is given in viewgraph form. Information is given on the Materials and Structures Division of NASA's Office of Aeronautics and Space Technology. The Division's space research and development budget is given. Further information is given on space materials and structures, space environmental effects, radiation effects, high temperature materials research, metal matrix composites, SiC fiber reinforced titanium alloys, structural dynamics, and control of flexible structures.

  16. Automating the application of smart materials for protein crystallization

    SciTech Connect

    Khurshid, Sahir; Govada, Lata; EL-Sharif, Hazim F.; Reddy, Subrayal M.; Chayen, Naomi E.

    2015-03-01

    The first semi-liquid, non-protein nucleating agent for automated protein crystallization trials is described. This ‘smart material’ is demonstrated to induce crystal growth and will provide a simple, cost-effective tool for scientists in academia and industry. The fabrication and validation of the first semi-liquid nonprotein nucleating agent to be administered automatically to crystallization trials is reported. This research builds upon prior demonstration of the suitability of molecularly imprinted polymers (MIPs; known as ‘smart materials’) for inducing protein crystal growth. Modified MIPs of altered texture suitable for high-throughput trials are demonstrated to improve crystal quality and to increase the probability of success when screening for suitable crystallization conditions. The application of these materials is simple, time-efficient and will provide a potent tool for structural biologists embarking on crystallization trials.

  17. Crystal structure refinement with SHELXL

    PubMed Central

    Sheldrick, George M.

    2015-01-01

    The improvements in the crystal structure refinement program SHELXL have been closely coupled with the development and increasing importance of the CIF (Crystallographic Information Framework) format for validating and archiving crystal structures. An important simplification is that now only one file in CIF format (for convenience, referred to simply as ‘a CIF’) containing embedded reflection data and SHELXL instructions is needed for a complete structure archive; the program SHREDCIF can be used to extract the .hkl and .ins files required for further refinement with SHELXL. Recent developments in SHELXL facilitate refinement against neutron diffraction data, the treatment of H atoms, the determination of absolute structure, the input of partial structure factors and the refinement of twinned and disordered structures. SHELXL is available free to academics for the Windows, Linux and Mac OS X operating systems, and is particularly suitable for multiple-core processors. PMID:25567568

  18. Crystal structure refinement with SHELXL

    SciTech Connect

    Sheldrick, George M.

    2015-01-01

    New features added to the refinement program SHELXL since 2008 are described and explained. The improvements in the crystal structure refinement program SHELXL have been closely coupled with the development and increasing importance of the CIF (Crystallographic Information Framework) format for validating and archiving crystal structures. An important simplification is that now only one file in CIF format (for convenience, referred to simply as ‘a CIF’) containing embedded reflection data and SHELXL instructions is needed for a complete structure archive; the program SHREDCIF can be used to extract the .hkl and .ins files required for further refinement with SHELXL. Recent developments in SHELXL facilitate refinement against neutron diffraction data, the treatment of H atoms, the determination of absolute structure, the input of partial structure factors and the refinement of twinned and disordered structures. SHELXL is available free to academics for the Windows, Linux and Mac OS X operating systems, and is particularly suitable for multiple-core processors.

  19. Crystal Growth and Intergrowth Structure of the New Heavy Fermion Materials CeIrIn 5 and CeRhIn 5

    NASA Astrophysics Data System (ADS)

    Moshopoulou, E. G.; Fisk, Z.; Sarrao, J. L.; Thompson, J. D.

    2001-04-01

    The structures of the new heavy fermion materials CeIrIn5 and CeRhIn5 have been determined by single-crystal neutron (R(F)=0.051) and X-ray (R(F)=0.056) diffraction, respectively. Both compounds adopt tetragonal structure, space group P4/mmm (No. 123), Z=1, a=b=4.674(1) Å, and c=7.501(5) Å for CeIrIn5, and a=b=4.656(2) Å, and c=7.542(1) Å for CeRhIn5. The possible presence of antisite disorder, a long-standing question on this type of structure, was excluded by both electron and-neutron or X-ray diffraction. The compounds are built by monolayers of face-sharing distorted cuboctahedra [CeIn3] and monolayers of edge-sharing rectangular parallelepipeds [RhIn2] or [IrIn2], stacked alternatively in the [001] direction. Therefore, they are new members of the inhomogeneous linear homologous series MmTnT‧3m+2n. Because of their ordered intergrowth structure, the physical properties of the quasi-two-dimensional heavy electron systems CeIrIn5 and CeRhIn5 can be directly compared with the corresponding ones of their parent compound, the three-dimensional heavy fermion material CeIn3.

  20. Crystal structure of pyrazoxyfen

    PubMed Central

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

    2015-01-01

    The title compound, C20H16Cl2N2O3 (systematic name: 2-{[4-(2,4-di­chloro­benzo­yl)-1,3-di­methyl­pyrazol-5-yl}­oxy}-1-phenyl­ethan-1-one), is the benzoyl­pyrazole herbicide pyrazoxyfen. The asymmetric unit comprises two independent mol­ecules, A and B, in which the pyrazole ring makes dihedral angles of 80.29 (10) and 61.70 (10)° and 87.60 (10) and 63.92 (8)°, respectively, with the di­chloro­phenyl and phenyl rings. In the crystal, C—H⋯O and C—H⋯N hydrogen bonds, and C—H⋯π and π–π [3.646 (2) Å] inter­actions link adjacent mol­ecules, forming a two-dimensional network parellel to (011). In addition, the networks are linked by weak inter­molecular C—Cl⋯π [3.356 (2), 3.950 (2), 3.250 (2) and 3.575 (2) Å] inter­actions, resulting in a three-dimensional architecture. PMID:26870483

  1. Crystal structure of pyrazoxyfen.

    PubMed

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

    2015-12-01

    The title compound, C20H16Cl2N2O3 (systematic name: 2-{[4-(2,4-di-chloro-benzo-yl)-1,3-di-methyl-pyrazol-5-yl}-oxy}-1-phenyl-ethan-1-one), is the benzoyl-pyrazole herbicide pyrazoxyfen. The asymmetric unit comprises two independent mol-ecules, A and B, in which the pyrazole ring makes dihedral angles of 80.29 (10) and 61.70 (10)° and 87.60 (10) and 63.92 (8)°, respectively, with the di-chloro-phenyl and phenyl rings. In the crystal, C-H⋯O and C-H⋯N hydrogen bonds, and C-H⋯π and π-π [3.646 (2) Å] inter-actions link adjacent mol-ecules, forming a two-dimensional network parellel to (011). In addition, the networks are linked by weak inter-molecular C-Cl⋯π [3.356 (2), 3.950 (2), 3.250 (2) and 3.575 (2) Å] inter-actions, resulting in a three-dimensional architecture. PMID:26870483

  2. Gallium Nitride Crystals: Novel Supercapacitor Electrode Materials.

    PubMed

    Wang, Shouzhi; Zhang, Lei; Sun, Changlong; Shao, Yongliang; Wu, Yongzhong; Lv, Jiaxin; Hao, Xiaopeng

    2016-05-01

    A type of single-crystal gallium nitride mesoporous membrane is fabricated and its supercapacitor properties are demonstrated for the first time. The supercapacitors exhibit high-rate capability, stable cycling life at high rates, and ultrahigh power density. This study may expand the range of crystals as high-performance electrode materials in the field of energy storage. PMID:27007502

  3. An insight into crystal, electronic, and local structures of lithium iron silicate (Li2FeSiO4) materials upon lithium extraction

    NASA Astrophysics Data System (ADS)

    Kamon-in, O.; Klysubun, W.; Limphirat, W.; Srilomsak, S.; Meethong, N.

    2013-05-01

    Recently, orthosilicate, Li2MSiO4 (where M=transition metal) materials have been attracting considerable attention for potential use as a new generation cathode for Li-ion batteries due to their safety, low toxicity, and low cost characteristics. In addition, the presence of two Li+ ions in the molecule offers a multiple electron-charge transfer (M2+/M3+ and M3+/M4+ redox couples), thus allowing a high achievable capacity of more than 320 mA h/g per M unit. Good electrochemical properties of Li2FeSiO4 have been reported through several approaches such as downsizing of the particles, carbon-coating, etc. However, in addition to electrochemical performance, fundamental understanding regarding crystal, electronic and local structure changes during charge/discharge processes is also important and needs more rigorous investigation. In this work, lithium iron silicates (Li2FeSiO4/C) in space group of Pnma: a=10.6671(3) Å, b=6.2689(2) Å, and c=5.0042(2) Å have been prepared by solid-state reaction. The synthesized as well as chemical delithiated samples have been characterized by XRD, HRTEM, AAS and XAS techniques. We will show the results focusing on Fe K-edge XANES, EXAFS, HRTEM and XRD of the Li2-xFeSiO4 samples and discuss how the crystal, electronic, and local structure changes upon Li+ de-intercalation.

  4. Synthesis and crystal structure of two tin fluoride materials: NaSnF 3 (BING-12) and Sn 3F 3PO 4

    NASA Astrophysics Data System (ADS)

    Salami, Tolulope O.; Zavalij, Peter Y.; Oliver, Scott R. J.

    2004-03-01

    A new compound, sodium tin trifluoride (NaSnF 3, which we denote BING-12 for SUNY at Binghamton, Structure No. 12), was synthesized solvothermally from a pyridine-water solvent system. The new compound crystallized in the monoclinic space group C2/ c (No. 15), with a=11.7429(12) Å, b=17.0104(18) Å, c=6.8528(7) Å, β=100.6969(2)°, V=1345.1(2) Å 3 and Z=16. The layered structure consists of outer pyramidal SnF 3 units, where the fluorides surround a central layer of six- and seven-coordinate sodium atoms. The layers are stabilized by charged Na + galleries that reside in the center of the layers. Tin trifluorophosphate (Sn 3F 3PO 4, Compound 2) was isolated from a related synthetic system, and crystallized in the rhombohedral space group R3 (No. 146), with a=11.8647(11) Å, c=4.6291(6) Å, V=564.34(10) Å 3 and Z=3. The framework is made up of helical -Sn-F- chains, which are connected by phosphate groups. The materials were characterized by powder X-ray diffraction (PXRD), variable temperature PXRD (VT-PXRD), thermogravimetric analysis (TGA) and scanning electron microscopy (SEM).

  5. Layered exfoliable crystalline materials based on Sm-, Eu- and Eu/Gd-2-phenylsuccinate frameworks. Crystal structure, topology and luminescence properties.

    PubMed

    Gomez, G E; Bernini, M C; Brusau, E V; Narda, G E; Vega, D; Kaczmarek, A M; Van Deun, R; Nazzarro, M

    2015-02-21

    Three new layered metal-organic frameworks (MOFs) based on 2-phenylsuccinic acid (H2psa) and lanthanide ions with the formula [Ln2(C10H8O4)3(H2O)] (Ln = Eu, Sm and Eu-Gd) have been synthesized under solvothermal conditions and fully characterized by single-crystal X-ray diffraction, thermal and vibrational analyses. The compounds are isostructural featuring 2D frameworks that consist of infinite zigzag chains composed of [LnO8] and [LnO8(H2O)] edge-sharing polyhedra linked by psa ligands leading to layers further connected by weak π-π interactions in an edge orientation. Moreover, a topological study was carried out to obtain the simplified net for better comparison with structurally related compounds. The crystals were exfoliated into nanolayers after miniaturization by addition of sodium acetate as a capping agent in the reaction medium. Scanning electron microscopy was applied to characterize the miniaturized samples whereas the exfoliated hybrid nanosheets were studied by atomic force microscopy. The photoluminescence (PL) properties of the bulk compounds as well as the miniaturized and exfoliated materials were investigated and compared with other related ones. An exhaustive study of the Eu(iii)-based MOFs was performed on the basis of the obtained PL parameters (excitation and emission spectra, kr, knr, intrinsic quantum yields and lifetimes) to explore the underlying structure-property relationships. PMID:25599977

  6. Structural materials and components

    NASA Technical Reports Server (NTRS)

    Gagliani, John (Inventor); Lee, Raymond (Inventor)

    1982-01-01

    High density structural (blocking) materials composed of a polyimide filled with glass microballoons. Structural components such as panels which have integral edgings and/or other parts made of the high density materials.

  7. Structural materials and components

    NASA Technical Reports Server (NTRS)

    Gagliani, John (Inventor); Lee, Raymond (Inventor)

    1983-01-01

    High density structural (blocking) materials composed of a polyimide filled with glass microballoons. Structural components such as panels which have integral edgings and/or other parts made of the high density materials.

  8. Lightweight Materials & Structures

    NASA Video Gallery

    The Lightweight Materials and Structures (LMS) project will mature high-payoff structures and materials technologies that have direct application to NASA’s future space exploration needs.One of the...

  9. Granular crystals: Nonlinear dynamics meets materials engineering

    SciTech Connect

    Porter, Mason A.; Kevrekidis, Panayotis G.; Daraio, Chiara

    2015-11-01

    In this article, the freedom to choose the size, stiffness, and spatial distribution of macroscopic particles in a lattice makes granular crystals easily tailored building blocks for shock-absorbing materials, sound-focusing devices, acoustic switches, and other exotica.

  10. Synthetic thermoelectric materials comprising phononic crystals

    SciTech Connect

    El-Kady, Ihab F; Olsson, Roy H; Hopkins, Patrick; Reinke, Charles; Kim, Bongsang

    2013-08-13

    Synthetic thermoelectric materials comprising phononic crystals can simultaneously have a large Seebeck coefficient, high electrical conductivity, and low thermal conductivity. Such synthetic thermoelectric materials can enable improved thermoelectric devices, such as thermoelectric generators and coolers, with improved performance. Such synthetic thermoelectric materials and devices can be fabricated using techniques that are compatible with standard microelectronics.

  11. Fundamental Studies of Crystal Growth of Microporous Materials

    NASA Technical Reports Server (NTRS)

    Dutta, P.; George, M.; Ramachandran, N.; Schoeman, B.; Curreri, Peter A. (Technical Monitor)

    2002-01-01

    Microporous materials are framework structures with well-defined porosity, often of molecular dimensions. Zeolites contain aluminum and silicon atoms in their framework and are the most extensively studied amongst all microporous materials. Framework structures with P, Ga, Fe, Co, Zn, B, Ti and a host of other elements have also been made. Typical synthesis of microporous materials involve mixing the framework elements (or compounds, thereof) in a basic solution, followed by aging in some cases and then heating at elevated temperatures. This process is termed hydrothermal synthesis, and involves complex chemical and physical changes. Because of a limited understanding of this process, most synthesis advancements happen by a trial and error approach. There is considerable interest in understanding the synthesis process at a molecular level with the expectation that eventually new framework structures will be built by design. The basic issues in the microporous materials crystallization process include: (1) Nature of the molecular units responsible for the crystal nuclei formation; (2) Nature of the nuclei and nucleation process; (3) Growth process of the nuclei into crystal; (4) Morphological control and size of the resulting crystal; (5) Surface structure of the resulting crystals; (6) Transformation of frameworks into other frameworks or condensed structures. The NASA-funded research described in this report focuses to varying degrees on all of the above issues and has been described in several publications. Following is the presentation of the highlights of our current research program. The report is divided into five sections: (1) Fundamental aspects of the crystal growth process; (2) Morphological and Surface properties of crystals; (3) Crystal dissolution and transformations; (4) Modeling of Crystal Growth; (5) Relevant Microgravity Experiments.

  12. Crystal structure of guggulsterone Z

    SciTech Connect

    Gupta, V. K. Bandhoria, P.; Gupta, B. D.; Gupta, K. K.

    2006-03-15

    The crystal structure of the title compound (4,17(20)-trans-pregnadiene-3,16-dione, C{sub 21}H{sub 28}O{sub 2}) has been determined by direct methods using single-crystal X-ray diffraction data. The compound crystallizes into the orthorhombic space group P2{sub 1}2{sub 1}2{sub 1} with the unit cell parameters a = 7.908(2) A, b = 13.611(3) A, c = 16.309(4) A, and Z = 4. The structure has been refined to R = 0.058 for 3667 observed reflections. The bond distances and angles are in good agreement with guggulsterone E and other related steroid molecules. Ring A exists in the distorted sofa conformation, while rings B and C adopt the distorted chair conformation. Five-membered ring D is intermediate between the half-chair and envelope conformations. The A/B ring junction is quasi-trans, while ring systems B/C and C/D are trans fused about the C(8)-C(9) and C(13)-C(14) bonds, respectively. The steroid nucleus has a small twist, as shown by the C(19)-C(10)...C(13)-C(18) pseudo-torsion angle of 7.2{sup o}. The crystal structure is stabilized by intra-and intermolecular C-H...O hydrogen bonds.

  13. Photonic Crystal Laser-Driven Accelerator Structures

    SciTech Connect

    Cowan, Benjamin M.

    2007-08-22

    Laser-driven acceleration holds great promise for significantly improving accelerating gradient. However, scaling the conventional process of structure-based acceleration in vacuum down to optical wavelengths requires a substantially different kind of structure. We require an optical waveguide that (1) is constructed out of dielectric materials, (2) has transverse size on the order of a wavelength, and (3) supports a mode with speed-of-light phase velocity in vacuum. Photonic crystals---structures whose electromagnetic properties are spatially periodic---can meet these requirements. We discuss simulated photonic crystal accelerator structures and describe their properties. We begin with a class of two-dimensional structures which serves to illustrate the design considerations and trade-offs involved. We then present a three-dimensional structure, and describe its performance in terms of accelerating gradient and efficiency. We discuss particle beam dynamics in this structure, demonstrating a method for keeping a beam confined to the waveguide. We also discuss material and fabrication considerations. Since accelerating gradient is limited by optical damage to the structure, the damage threshold of the dielectric is a critical parameter. We experimentally measure the damage threshold of silicon for picosecond pulses in the infrared, and determine that our structure is capable of sustaining an accelerating gradient of 300 MV/m at 1550 nm. Finally, we discuss possibilities for manufacturing these structures using common microfabrication techniques.

  14. Electron diffraction and high-resolution transmission electron microscopy of the high temperature crystal structures of GexSb2Te3+x (x=1,2,3) phase change material

    NASA Astrophysics Data System (ADS)

    Kooi, B. J.; De Hosson, J. Th. M.

    2002-10-01

    The crystal structures of GeSb2Te4, Ge2Sb2Te5, and Ge3Sb2Te6 were determined using electron diffraction and high-resolution transmission electron microscopy. The structure determined for the former two crystals deviates from the ones proposed in the literature. These crystal structures were developed jointly upon cooling of liquid Ge2Sb2Te5. A stacking disorder parallel to the basal plane was observed that increases with increasing cooling rates. For the GexSb2Te3+x (x=1,2,3) crystals it is shown that an a,b,c stacking holds with an alternating stacking of x GeTe double layers identically present in binary GeTe and one Te-Sb-Te-Te-Sb- repeat unit also present in binary Sb2Te3. A stacking disorder is a logical consequence of building crystals with these two principal units. On the other hand, it is likely that all stable crystals of the Ge-Sb-Te systems are an ordered sequence of these two units. Some of the implications of these findings of the stable and metastable crystal structures that develop from amorphous Ge2Sb2Te5 are presented so as to understand the crucial crystallization process in Ge2Sb2Te5 phase change material.

  15. Fundamental Studies of Crystal Growth of Microporous Materials

    NASA Technical Reports Server (NTRS)

    Singh, Ramsharan; Doolittle, John, Jr.; Payra, Pramatha; Dutta, Prabir K.; George, Michael A.; Ramachandran, Narayanan; Schoeman, Brian J.

    2003-01-01

    Microporous materials are framework structures with well-defined porosity, often of molecular dimensions. Zeolites contain aluminum and silicon atoms in their framework and are the most extensively studied amongst all microporous materials. Framework structures with P, Ga, Fe, Co, Zn, B, Ti and a host of other elements have also been made. Typical synthesis of microporous materials involve mixing the framework elements (or compounds, thereof) in a basic solution, followed by aging in some cases and then heating at elevated temperatures. This process is termed hydrothermal synthesis, and involves complex chemical and physical changes. Because of a limited understanding of this process, most synthesis advancements happen by a trial and error approach. There is considerable interest in understanding the synthesis process at a molecular level with the expectation that eventually new framework structures will be built by design. The basic issues in the microporous materials crystallization process include: (a) Nature of the molecular units responsible for the crystal nuclei formation; (b) Nature of the nuclei and nucleation process; (c) Growth process of the nuclei into crystal; (d) Morphological control and size of the resulting crystal; (e) Surface structure of the resulting crystals; and (f) Transformation of frameworks into other frameworks or condensed structures.

  16. The crystal structure and crystal chemistry of fernandinite and corvusite

    USGS Publications Warehouse

    Evans, H.T., Jr.; Post, J.E.; Ross, D.R.; Nelen, J.A.

    1994-01-01

    Using type material of fernandinite from Minasragra, Peru, and corvusite from the Jack Claim, La Sal Mountains, Utah, the properties and crystal chemistry of these minerals have been determined by Rietveld analysis of the powder X-ray-diffraction patterns. The crystal structure of both species is isotypic with the V2O5 -type layer first found for ??-Ag0.68V2O5; it consists of chains of VO6 octahedra linked by opposite corners (parallel to b) condensed by edge-sharing to form the layer. The vanadium has average valence 4.8, and the resulting layer-charge is balanced by varying amounts of Ca, Na, and K in the interlayer region accompanied by labile water. This study has confirmed the validity of fernandinite as a unique mineral species. It is closely related to corvusite, from which it is distinguished on the basis of the dominant interlayer cation: Ca for fernandinite, Na for curvusite. -Authors

  17. An Example of Body-Centered Cubic Crystal Structure: The Atomium in Brussels as an Educative Tool for Introductory Materials Chemistry

    ERIC Educational Resources Information Center

    Pinto, Gabriel

    2012-01-01

    When students are introduced to the ways in which atoms are arranged in crystal structures, transposing the textbook illustrations into three-dimensional structures is difficult for some of them. To facilitate this transition, this article describes an approach to the study of the structure of solids through a well-known monument, the Atomium in…

  18. The Surface Structure of Ground Metal Crystals

    NASA Technical Reports Server (NTRS)

    Boas, W.; Schmid, E.

    1944-01-01

    The changes produced on metallic surfaces as a result of grinding and polishing are not as yet fully understood. Undoubtedly there is some more or less marked change in the crystal structure, at least, in the top layer. Hereby a diffusion of separated crystal particles may be involved, or, on plastic material, the formation of a layer in greatly deformed state, with possible recrystallization in certain conditions. Czochralski verified the existence of such a layer on tin micro-sections by successive observations of the texture after repeated etching; while Thomassen established, roentgenographically by means of the Debye-Scherrer method, the existence of diffused crystal fractions on the surface of ground and polished tin bars, which he had already observed after turning (on the lathe). (Thickness of this layer - 0.07 mm). Whether this layer borders direct on the undamaged base material or whether deformed intermediate layers form the transition, nothing is known. One observation ty Sachs and Shoji simply states that after the turning of an alpha-brass crystal the disturbance starting from the surface, penetrates fairly deep (approx. 1 mm) into the crystal (proof by recrystallization at 750 C).

  19. Design and realization of one-dimensional double hetero-structure photonic crystals for infrared-radar stealth-compatible materials applications

    SciTech Connect

    Wang, Zhixun; Cheng, Yongzhi Nie, Yan; Wang, Xian; Gong, Rongzhou

    2014-08-07

    In this paper, a new type one-dimensional (1D) double hetero-structure composite photonic crystal (CPC) for infrared-radar stealth-compatible materials applications was proposed and studied numerically and experimentally. First, based on transfer matrix method of thin-film optical theory, the propagation characteristics of the proposed structure comprising a stack of different alternating micrometer-thick layers of germanium and zinc sulfide were investigated numerically. Calculation results exhibit that this 1D single hetero-structure PC could achieve a flat high reflectivity gradually with increasing the number of the alternating media layers in a single broadband range. Then, based on principles of distributed Bragg reflector micro-cavity, a 1D double hetero-structure CPC comprising four PCs with thickness of 0.797 μm, 0.592 μm, 1.480 μm, and 2.114 μm, respectively, was proposed. Calculation results exhibit that this CPC could achieve a high reflectance of greater than 0.99 in the wavelength ranges of 3–5 μm and 8–14 μm and agreed well with experiment. Further experiments exhibit that the infrared emissivity of the proposed CPC is as low as 0.073 and 0.042 in the wavelength ranges of 3–5 μm and 8–12 μm, respectively. In addition, the proposed CPC can be used to construct infrared-radar stealth-compatible materials due to its high transmittance in radar wave band.

  20. Crystal structure and chemistry of a complex indium phosphate framework material, (ethylenediammonium)In{sub 3}P{sub 3}O{sub 12}(OH){sub 2}

    SciTech Connect

    Broach, Robert W.; Bedard, Robert L.; King, Lisa M.; Pluth, Joseph J.; Smith, Joseph V.; Kirchner, Richard M.

    2012-12-15

    The chemistry and structure of a novel indium phosphate material (RIPS-4), (H{sub 3}NCH{sub 2}CH{sub 2}NH{sub 3})In{sub 3}-P{sub 3}O{sub 12}(OH){sub 2}, are described. RIPS-4 was synthesized using ethylene diamine as a structure-directing organic agent. The X-ray crystal structure was determined from a 12 Multiplication-Sign 12 Multiplication-Sign 42 {mu}m{sup 3} crystal in space group C2/m with a=18.662(4) A, b=6.600(2) A, c=12.573(3) A and {beta}=120.92(1) Degree-Sign . The structure consists of a complex edge- and vertex-shared open framework of InO{sub 6} octahedra and PO{sub 4} tetrahedra enclosing cavities occupied by ethylenediamonium ions. One set of octahedra share opposing edges to form chains along the b-axis matching the structural unit in rutile (TiO{sub 2}). This rutile edge-shared chain has its projecting oxygen atoms shared with the vertexes of either a PO{sub 4} tetrahedron or a second type of InO{sub 6} octahedron. The O atoms are 2-connected, each to one In and one P, except for two protonated O atoms (hydroxyl groups) that connect to two and three In atoms, giving three- and four-coordinate O atoms, respectively. - Graphical abstract: The unique topology contains an unusual 4-connected oxygen atom (O{sub 1}) in a complex edge- and vertex-shared open framework of InO{sub 6} octahedra (blue) and PO{sub 4} tetrahedra (yellow) that encloses cavities occupied by ethylenediammonium ions. Highlights: Black-Right-Pointing-Pointer The structure has a unique open-framework topology. Black-Right-Pointing-Pointer The framework contains an unusual 4-connected oxygen atom. Black-Right-Pointing-Pointer Hydrogen bonds hold the ethylenediammonium ions in the cavities.

  1. Modeling Polymorphic Molecular Crystals with Electronic Structure Theory.

    PubMed

    Beran, Gregory J O

    2016-05-11

    Interest in molecular crystals has grown thanks to their relevance to pharmaceuticals, organic semiconductor materials, foods, and many other applications. Electronic structure methods have become an increasingly important tool for modeling molecular crystals and polymorphism. This article reviews electronic structure techniques used to model molecular crystals, including periodic density functional theory, periodic second-order Møller-Plesset perturbation theory, fragment-based electronic structure methods, and diffusion Monte Carlo. It also discusses the use of these models for predicting a variety of crystal properties that are relevant to the study of polymorphism, including lattice energies, structures, crystal structure prediction, polymorphism, phase diagrams, vibrational spectroscopies, and nuclear magnetic resonance spectroscopy. Finally, tools for analyzing crystal structures and intermolecular interactions are briefly discussed. PMID:27008426

  2. Composite structural materials

    NASA Technical Reports Server (NTRS)

    Loewy, R. G.; Wiberley, S. E.

    1985-01-01

    Various topics relating to composite structural materials for use in aircraft structures are discussed. The mechanical properties of high performance carbon fibers, carbon fiber-epoxy interface bonds, composite fractures, residual stress in high modulus and high strength carbon fibers, fatigue in composite materials, and the mechanical properties of polymeric matrix composite laminates are among the topics discussed.

  3. Crystallization of Oxides as Functional Materials

    NASA Astrophysics Data System (ADS)

    Sun, Congting; Song, Shuyan; Xue, Dongfeng; Zhang, Hongjie

    2012-06-01

    Crystallization is essential to the manufacture of functional materials as varies as electronic devices, energy storage and conversion devices, and highly reactive catalysts. As an important part of functional materials, metal oxides possess wide applications and the crystallization of oxide materials has thus received considerable attention from both fundamental and technological perspectives. With particular emphasis on our recent laboratory results, this feature article gives a brief review in the field of crystallization of oxides. On the basis of chemical bonding theory of single crystal growth, we have simulated thermodynamic growth behaviors of various functional oxides such as ZnO, MgO, Cu2O, Nb2O5, V2O5, MnO2, SnO2, NiO, KDP/ADP, LiNbO3, and NaNbO3. Quantitatively analyzing bonding conditions of controllable crystallographic faces enables us to design proper synthesis strategies and optimize growth parameters, consequently obtaining functional oxides with desirable crystallization behaviors.

  4. Structural, optical, thermal, photoconductivity, laser damage threshold and fluorescence analysis of an organic material: β-P-amino benzoic acid single crystal

    NASA Astrophysics Data System (ADS)

    Chandran, SenthilKumar; Paulraj, Rajesh; Ramasamy, P.

    2016-02-01

    β-P-amino benzoic acid, an organic single crystal was grown by slow evaporation technique. Single crystal X-ray diffraction studies show that the grown crystal has β-polymorph of P-amino benzoic acid [β-PABA] form and the lattice parameters are a = 6.30 Å, b = 8.61 Å, c = 12.43 Å α = γ = 90° and β = 100.20°. FTIR analysis confirms that bands at 1588 cm-1, 1415 cm-1 are assigned to ring skeletal vibrations of title compound. The molecular structure of the grown crystal has been identified by Nuclear Magnetic Resonance spectral study. The optical absorbance spectrum from 200 to 1100 nm shows that there is an edge absorbance in UV region. Optical band gap of the crystal has been assessed from the absorbance spectrum. The thermal properties of crystals were evaluated from TG-DTA analysis, it exhibits that there is no weight loss up to 187 °C. Laser damage threshold indicates that the grown crystal has no surface damage up to 35 mJ. Photoconductivity and fluorescence spectral experiments are also carried out and the results are discussed.

  5. Three-Dimensional Photonic Crystal Laser-Driven Accelerator Structures

    SciTech Connect

    Cowan, B.; /SLAC

    2006-09-07

    We discuss simulated photonic crystal structure designs for laser-driven particle acceleration, focusing on three-dimensional planar structures based on the so-called ''woodpile'' lattice. We describe guiding of a speed-of-light accelerating mode by a defect in the photonic crystal lattice and discuss the properties of this mode, including particle beam dynamics and potential coupling methods for the structure. We also discuss possible materials and power sources for this structure and their effects on performance parameters, as well as possible manufacturing techniques and the required tolerances. In addition we describe the computational technique and possible improvements in numerical modeling that would aid development of photonic crystal structures.

  6. Iodobismuthates Containing One-Dimensional BiI4(-) Anions as Prospective Light-Harvesting Materials: Synthesis, Crystal and Electronic Structure, and Optical Properties.

    PubMed

    Yelovik, Natalie A; Mironov, Andrei V; Bykov, Mikhail A; Kuznetsov, Alexey N; Grigorieva, Anastasia V; Wei, Zheng; Dikarev, Evgeny V; Shevelkov, Andrei V

    2016-05-01

    Four iodobismuthates, LiBiI4·5H2O (1), MgBi2I8·8H2O (2), MnBi2I8·8H2O (3), and KBiI4·H2O (4), were prepared by a facile solution route and revealed thermal stability in air up to 120 °C. Crystal structures of compounds 1-4 were solved by a single crystal X-ray diffraction method. 1: space group C2/c, a = 12.535(2), b = 16.0294(18), c = 7.6214(9) Å, β = 107.189(11)°, Z = 4, R = 0.029. 2: space group P21/c, a = 7.559(2), b = 13.1225(15), c = 13.927(4) Å, β = 97.14(3)°, Z = 2, R = 0.031. 3: space group P21/c, a = 7.606(3), b = 13.137(3), c = 14.026(5) Å, β = 97.14(3)°, Z = 2, R = 0.056. 4: space group P21/n, a = 7.9050(16), b = 7.7718(16), c = 18.233(4) Å, β = 97.45(3)°, Z = 4, R = 0.043. All solid state structures feature one-dimensional (BiI4)(-) anionic chains built of [BiI6] octahedra that share two opposite edges in such a fashion that two iodine atoms in cis-positions remain terminal. The calculated electronic structures and observed optical properties confirmed that compounds 1-4 are semiconductors with direct band gaps of 1.70-1.76 eV, which correspond to their intense red color. It was shown that the cations do not affect the optical properties, and the optical absorption is primarily associated with the charge transfer from the I 5p orbitals at the top of the valence band to the Bi 6p orbitals at the bottom of the conduction band. Based on their properties and facile synthesis, the title compounds are proposed as promising light-harvesting materials for all-solid solar cells. PMID:27074093

  7. Composite structural materials. [aircraft structures

    NASA Technical Reports Server (NTRS)

    Ansell, G. S.; Loewy, R. G.; Wiberley, S. E.

    1980-01-01

    The use of filamentary composite materials in the design and construction of primary aircraft structures is considered with emphasis on efforts to develop advanced technology in the areas of physical properties, structural concepts and analysis, manufacturing, and reliability and life prediction. The redesign of a main spar/rib region on the Boeing 727 elevator near its actuator attachment point is discussed. A composite fabrication and test facility is described as well as the use of minicomputers for computer aided design. Other topics covered include (1) advanced structural analysis methids for composites; (2) ultrasonic nondestructive testing of composite structures; (3) optimum combination of hardeners in the cure of epoxy; (4) fatigue in composite materials; (5) resin matrix characterization and properties; (6) postbuckling analysis of curved laminate composite panels; and (7) acoustic emission testing of composite tensile specimens.

  8. Composite structural materials

    NASA Technical Reports Server (NTRS)

    Loewy, R.; Wiberley, S. E.

    1986-01-01

    Overall emphasis is on basic long-term research in the following categories: constituent materials, composite materials, generic structural elements, processing science technology; and maintaining long-term structural integrity. Research in basic composition, characteristics, and processing science of composite materials and their constituents is balanced against the mechanics, conceptual design, fabrication, and testing of generic structural elements typical of aerospace vehicles so as to encourage the discovery of unusual solutions to present and future problems. Detailed descriptions of the progress achieved in the various component parts of this comprehensive program are presented.

  9. Impact of crystal structure singularity on transport and electrochemical properties of Lix(LiyFezV1‑y‑z)O2 — electrode material for lithium batteries

    NASA Astrophysics Data System (ADS)

    Gędziorowski, Bartłomiej; Tobola, Janusz; Braun, Artur; Molenda, Janina

    2016-07-01

    Lithium vanadium oxide (LiVO2) and its substituted derivatives are a distinctive group of materials that may act both, as cathode and anode materials for Li-ion batteries. This paper presents influence of crystal structure singularity of Li(LiyFezV1‑y‑z)O2 (y=0, 0.03, 0.07, z=0, 0.05, 0.1) on transport and electrochemical properties of the compounds.

  10. Spectroscopic, thermal and structural studies on manganous malate crystals

    SciTech Connect

    Thomas, J. Lincy, A. Mahalakshmi, V.; Saban, K. V.

    2013-01-15

    Prismatic crystals of manganous malate have been prepared by controlled ionic diffusion in hydrosilica gel. The structure was elucidated using single crystal X-ray diffraction. The crystals are orthorhombic with space group Pbca. Vibrations of the functional groups were identified by the FTIR spectrum. Thermogravimetric and differential thermal analyses (TG-DTA) were carried out to explore the thermal decomposition pattern of the material. Structural information derived from FTIR and TG-DTA studies is in conformity with the single crystal XRD data.

  11. Predicting polymeric crystal structures by evolutionary algorithms

    NASA Astrophysics Data System (ADS)

    Zhu, Qiang; Sharma, Vinit; Oganov, Artem R.; Ramprasad, Ramamurthy

    2014-10-01

    The recently developed evolutionary algorithm USPEX proved to be a tool that enables accurate and reliable prediction of structures. Here we extend this method to predict the crystal structure of polymers by constrained evolutionary search, where each monomeric unit is treated as a building block with fixed connectivity. This greatly reduces the search space and allows the initial structure generation with different sequences and packings of these blocks. The new constrained evolutionary algorithm is successfully tested and validated on a diverse range of experimentally known polymers, namely, polyethylene, polyacetylene, poly(glycolic acid), poly(vinyl chloride), poly(oxymethylene), poly(phenylene oxide), and poly (p-phenylene sulfide). By fixing the orientation of polymeric chains, this method can be further extended to predict the structures of complex linear polymers, such as all polymorphs of poly(vinylidene fluoride), nylon-6 and cellulose. The excellent agreement between predicted crystal structures and experimentally known structures assures a major role of this approach in the efficient design of the future polymeric materials.

  12. Composite structural materials

    NASA Technical Reports Server (NTRS)

    Ansell, G. S.; Wiberley, S. E.

    1978-01-01

    The purpose of the RPI composites program is to develop advanced technology in the areas of physical properties, structural concepts and analysis, manufacturing, reliability and life prediction. Concommitant goals are to educate engineers to design and use composite materials as normal or conventional materials. A multifaceted program was instituted to achieve these objectives.

  13. Novel Microstructures for Polymer-Liquid Crystal Composite Materials

    NASA Technical Reports Server (NTRS)

    Magda, Jules J.

    2004-01-01

    There are a number of interface-dominated composite materials that contain a liquid crystalline (LC) phase in intimate contact with an isotropic phase. For example, polymer- dispersed liquid crystals, used in the fabrication of windows with switchable transparency, consist of micron size LC droplets dispersed in an isotropic polymer matrix. Many other types of liquid crystal composite materials can be envisioned that might have outstanding optical properties that could be exploited in novel chemical sensors, optical switches, and computer displays. This research project was based on the premise that many of these potentially useful LC composite materials can only be fabricated under microgravity conditions where gravity driven flows are absent. In the ground-based research described below, we have focused on a new class of LC composites that we call thermotropic- lyotropic liquid crystal systems (TLLCs). TLLCs consist of nanosize droplets of water dispersed in an LC matrix, with surfactants at the interface that stabilize the structure. By varying the type of surfactant one can access almost an infinite variety of unusual LC composite microstructures. Due to the importance of the interface in these types of systems, we have also developed molecular simulation models for liquid crystals at interfaces, and made some of the first measurements of the interfacial tension between liquid crystals and water.

  14. Composite structural materials

    NASA Technical Reports Server (NTRS)

    Ansell, G. S.; Loewy, R. G.; Wiberley, S. E.

    1982-01-01

    The promise of filamentary composite materials, whose development may be considered as entering its second generation, continues to generate intense interest and applications activity. Fiber reinforced composite materials offer substantially improved performance and potentially lower costs for aerospace hardware. Much progress has been achieved since the initial developments in the mid 1960's. Rather limited applications to primary aircraft structure have been made, however, mainly in a material-substitution mode on military aircraft, except for a few experiments currently underway on large passenger airplanes in commercial operation. To fulfill the promise of composite materials completely requires a strong technology base. NASA and AFOSR recognize the present state of the art to be such that to fully exploit composites in sophisticated aerospace structures, the technology base must be improved. This, in turn, calls for expanding fundamental knowledge and the means by which it can be successfully applied in design and manufacture.

  15. Composite structural materials

    NASA Technical Reports Server (NTRS)

    Ansell, G. S.; Loewy, R. G.; Wiberley, S. E.

    1984-01-01

    Progress is reported in studies of constituent materials composite materials, generic structural elements, processing science technology, and maintaining long-term structural integrity. Topics discussed include: mechanical properties of high performance carbon fibers; fatigue in composite materials; experimental and theoretical studies of moisture and temperature effects on the mechanical properties of graphite-epoxy laminates and neat resins; numerical investigations of the micromechanics of composite fracture; delamination failures of composite laminates; effect of notch size on composite laminates; improved beam theory for anisotropic materials; variation of resin properties through the thickness of cured samples; numerical analysis composite processing; heat treatment of metal matrix composites, and the RP-1 and RP2 gliders of the sailplane project.

  16. Composite structural materials

    NASA Technical Reports Server (NTRS)

    Ansell, G. S.; Loewy, R. G.; Wiberley, S. E.

    1979-01-01

    A multifaceted program is described in which aeronautical, mechanical, and materials engineers interact to develop composite aircraft structures. Topics covered include: (1) the design of an advanced composite elevator and a proposed spar and rib assembly; (2) optimizing fiber orientation in the vicinity of heavily loaded joints; (3) failure mechanisms and delamination; (4) the construction of an ultralight sailplane; (5) computer-aided design; finite element analysis programs, preprocessor development, and array preprocessor for SPAR; (6) advanced analysis methods for composite structures; (7) ultrasonic nondestructive testing; (8) physical properties of epoxy resins and composites; (9) fatigue in composite materials, and (10) transverse thermal expansion of carbon/epoxy composites.

  17. Composite Structural Materials

    NASA Technical Reports Server (NTRS)

    Ansell, G. S.; Loewy, R. G.; Wiberly, S. E.

    1984-01-01

    The development and application of filamentary composite materials, is considered. Such interest is based on the possibility of using relatively brittle materials with high modulus, high strength, but low density in composites with good durability and high tolerance to damage. Fiber reinforced composite materials of this kind offer substantially improved performance and potentially lower costs for aerospace hardware. Much progress has been made since the initial developments in the mid 1960's. There were only limited applied to the primary structure of operational vehicles, mainly as aircrafts.

  18. Crystal structure of prethrombin-1

    SciTech Connect

    Chen, Zhiwei; Pelc, Leslie A.; Di Cera, Enrico

    2010-11-15

    Prothrombin is the zymogen precursor of the clotting enzyme thrombin, which is generated by two sequential cleavages at R271 and R320 by the prothrombinase complex. The structure of prothrombin is currently unknown. Prethrombin-1 differs from prothrombin for the absence of 155 residues in the N-terminal domain and is composed of a single polypeptide chain containing fragment 2 (residues 156-271), A chain (residues 272-320), and B chain (residues 321-579). The X-ray crystal structure of prethrombin-1 solved at 2.2-{angstrom} resolution shows an overall conformation significantly different (rmsd = 3.6 {angstrom}) from that of its active form meizothrombin desF1 carrying a cleavage at R320. Fragment 2 is rotated around the y axis by 29{sup o} and makes only few contacts with the B chain. In the B chain, the oxyanion hole is disrupted due to absence of the I16-D194 ion pair and the Na{sup +} binding site and adjacent primary specificity pocket are highly perturbed. A remarkable feature of the structure is that the autolysis loop assumes a helical conformation enabling W148 and W215, located 17 {angstrom} apart in meizothrombin desF1, to come within 3.3 {angstrom} of each other and completely occlude access to the active site. These findings suggest that the zymogen form of thrombin possesses conformational plasticity comparable to that of the mature enzyme and have significant implications for the mechanism of prothrombin activation and the zymogen {yields} protease conversion in trypsin-like proteases.

  19. Composite structural materials

    NASA Technical Reports Server (NTRS)

    Ansell, G. S.; Loewy, R. G.; Wiberley, S. E.

    1982-01-01

    Research in the basic composition, characteristics, and processng science of composite materials and their constituents is balanced against the mechanics, conceptual design, fabrication, and testing of generic structural elements typical of aerospace vehicles so as to encourage the discovery of unusual solutions to problems. Detailed descriptions of the progress achieved in the various component parts of his program are presented.

  20. Materials and structures technology

    NASA Technical Reports Server (NTRS)

    Signorelli, R. A.; Glasgow, T. K.; Halford, G. R.; Levine, S. R.

    1979-01-01

    Materials and structures performance limitations, particularly for the hot section of the engine in which these limitations limit the life of components, are considered. Failure modes for components such as blades, vanes, and combustors and how they are affected by the environment for such components are discussed. Methods used to improve the materials used for such components are: (1) application of directional structures to turbine components for high strength at high temperatures; (2) improved coatings to increase oxidation and corrosion resistance; (3) increase strength and stiffness with reduced weight by applying higher specific properties of composite materials; and (4) cost effective processing such as near net shape powder methods applied to disks. Life prediction techniques developed to predict component life accurately in advance of service and progress in improving the intermediate and cold section components of turbine engines are covered.

  1. Photonic Crystal Laser-Driven Accelerator Structures

    SciTech Connect

    Cowan, B.; /SLAC

    2005-09-19

    We discuss simulated photonic crystal structure designs for laser-driven particle acceleration, focusing on three-dimensional planar structures based on the so-called ''woodpile'' lattice. We demonstrate guiding of a speed-of-light accelerating mode by a defect in the photonic crystal lattice and discuss the properties of this mode. We also discuss particle beam dynamics in the structure, presenting a novel method for focusing the beam. In addition we describe some potential coupling methods for the structure.

  2. Optical phonon modes and crystal structure of NaLaF4 single crystals

    NASA Astrophysics Data System (ADS)

    Lage, Márcio Martins; Matinaga, Franklin Massami; Gesland, Jean-Yves; Moreira, Roberto Luiz

    2006-03-01

    Polarized Raman scattering and infrared reflectivity measurements have been used to investigate the crystal structure of Czochralski-grown NaLaF4 single crystals. The phonon symmetries, the simultaneous presence of polar modes in the infrared and Raman spectra, as well as the observation of piezoelectric resonance, helped us to identify the P6 group as the correct one for this crystal. This material belongs to a family of sodium lanthanide tetrafluorides (NaLnF4) crystals, whose photoluminescence efficiency is comparable to LiYF4. Therefore, NaLaF4 crystals may be important in the development of diode pumped up-conversion solid-state lasers. The number and behavior of the observed optical phonon modes were analyzed in terms of group theory predictions for the group symmetry found. A few anomalies in the phonon characteristics are discussed in terms of cationic disorder in the crystal lattice.

  3. Structural, spectral and mechanical studies of bimetallic crystal: cadmium manganese thiocyanate single crystals

    NASA Astrophysics Data System (ADS)

    Manikandan, M.; Vijaya Prasath, G.; Bhagavannarayan, G.; Vijayan, N.; Mahalingam, T.; Ravi, G.

    2012-09-01

    A nonlinear optical bimetallic thiocyanate complex crystal, cadmium manganese thiocyanate (CMTC) has been successfully synthesized. The growth of single crystals of cadmium manganese thiocyanate has been accomplished from aqueous solution using slow evaporation method. The presence of manganese and cadmium in the synthesized material was confirmed through energy dispersive spectrum (EDS) analysis. Structural analysis was carried out using powder X-ray diffractometer (PXRD) and crystalline perfection of the grown crystals was ascertained by high-resolution X-ray diffraction (HRXRD) analysis. Fourier transform infrared (FTIR) spectrum was taken to confirm the functional groups. The transmittance spectrum of the crystal in the UV-visible region has been recorded and the cutoff wavelength has been determined. The dielectric measurements for the crystals were performed for various frequencies and temperatures. The mechanical properties were evaluated by Vickers microhardness testing, which reveals hardness and stiffness constant of the crystals.

  4. Crystal and electronic structure change determined by various method for delithiation process of Li x(Ni,Mn)O 2-based cathode material

    NASA Astrophysics Data System (ADS)

    Sekizawa, Oki; Hasegawa, Takuya; Kitamura, Naoto; Idemoto, Yasushi

    We investigated effects of delithiation on crystal, electronic structure, thermodynamic stability and physical property of Li xNi 0.5Mn 0.5O 2 by using a chemical delithiation treatment with ammonium peroxodisulfate, and compared the results with those of electrochemical delithiation. X-ray diffraction and thermodynamic data indicated that there was no phase transition in the samples after the chemical delithiation treatment within the lithium range of 0.50 ≤ x ≤ 1.00. From the ICP measurements and potentiometric titration, it was found that the chemical treatment successfully remove Li from the structure without any elution of Ni and Mn, but it accompanied O 2 removal at an initial process of the delithiation, i.e. 0.80 ≤ x ≤ 1.00. Crystal and electronic structure analyses also suggested such a O 2 removal at the lithium content range in the chemical delithiation method, although the estimated structure changes below x = 0.80 showed similar tendencies to those by the electrochemical delithiation.

  5. Synthesis, crystal structure, physico-chemical characterization and dielectric properties of a new hybrid material, 1-Ethylpiperazine-1,4-diium tetrachlorocadmate

    NASA Astrophysics Data System (ADS)

    Dhieb, A. C.; Valkonen, A.; Rzaigui, M.; Smirani, W.

    2015-12-01

    A new organic-inorganic hybrid metal complex, 1-Ethylpiperazine-1,4-diium tetrachlorocadmate was synthesized and the structure is determined by single crystal X-Ray diffraction analyses. The title compound crystallizes in the orthorhombic system with space group Pbca. The unit cell parameters are a = 11.5129 (2) Å, b = 9.7801 (2) Å, c = 23.8599 (4) Å with Z = 8 and V = 2686.56 (8) Å3. The examination of the structure shows that Cd(II) is coordinated by 4 chlorine atoms and adopt a tetrahedral geometry. Three-dimensional frameworks of the title compound are produced by N-H⋯Cl and C-H⋯Cl hydrogen bonding. IR, Raman and UV-Visible spectroscopies were also used to characterize this complex. Moreover, the fluorescent properties of the compound have been investigated in the solid state at room temperature. Solid state 13C MAS NMR spectroscopy results are in agreement with the X-ray structure. Differential scanning calorimetry (DSC) has revealed a structural phase transition of the order-disorder type around 373 K, and dielectric measurements were performed to discuss the mechanism of this phase transition. The evolution of dielectric constant as a function of temperature of the sample has been investigated in order to determine some related parameters.

  6. Accumulated distribution of material gain at dislocation crystal growth

    NASA Astrophysics Data System (ADS)

    Rakin, V. I.

    2016-05-01

    A model for slowing down the tangential growth rate of an elementary step at dislocation crystal growth is proposed based on the exponential law of impurity particle distribution over adsorption energy. It is established that the statistical distribution of material gain on structurally equivalent faces obeys the Erlang law. The Erlang distribution is proposed to be used to calculate the occurrence rates of morphological combinatorial types of polyhedra, presenting real simple crystallographic forms.

  7. Crystal structure of benzimidazolium salicylate

    PubMed Central

    Amudha, M.; Kumar, P. Praveen; Chakkaravarthi, G.

    2015-01-01

    In the anion of the title mol­ecular salt, C7H7N2 +·C7H5O3 − (systematic name: 1H-benzimidazol-3-ium 2-hy­droxy­ben­zo­ate), there is an intra­molecular O—H⋯O hydrogen bond that generates an S(6) ring motif. The CO2 group makes a dihedral angle of 5.33 (15)° with its attached ring. In the crystal, the dihedral angle between the benzimidazolium ring and the anion benzene ring is 75.88 (5)°. Two cations bridge two anions via two pairs of N—H⋯O hydrogen bonds, enclosing an R 4 4(16) ring motif, forming a four-membered centrosymmetric arrangement. These units are linked via C—H⋯O hydrogen bonds, forming chains propagating along the b-axis direction. The chains are linked by C—H⋯π and π–π inter­actions [inter-centroid distances = 3.4156 (7) and 3.8196 (8) Å], forming a three-dimensional structure. PMID:26594483

  8. Crystal structure of a perfect carbyne

    SciTech Connect

    Belenkov, E. A. Mavrinsky, V. V.

    2008-01-15

    The crystal structure of a perfect carbyne is calculated by the molecular mechanics methods. It is established that the carbyne crystals should consist of polycumulene chains arranged in hexagonal bundles. The unit cell of the perfect carbyne crystal is trigonal and contains one carbon atom. The unit cell parameters are as follows: a = b = c = 0.3580 nm, {alpha} = {beta} = {gamma} = 118.5{sup o}, and space group P3m1. The perfect carbyne single crystals have a stable structure at room temperature if the length of their constituent chains is larger than 500 nm.

  9. Liquid-crystal materials find a new order in biomedical applications

    NASA Astrophysics Data System (ADS)

    Woltman, Scott J.; Jay, Gregory D.; Crawford, Gregory P.

    2007-12-01

    With the maturation of the information display field, liquid-crystal materials research is undergoing a modern-day renaissance. Devices and configurations based on liquid-crystal materials are being developed for spectroscopy, imaging and microscopy, leading to new techniques for optically probing biological systems. Biosensors fabricated with liquid-crystal materials can allow label-free observations of biological phenomena. Liquid-crystal polymers are starting to be used in biomimicking colour-producing structures, lenses and muscle-like actuators. New areas of application in the realms of biology and medicine are stimulating innovation in basic and applied research into these materials.

  10. Synthesis, crystal structure, and spectroscopic studies of organic-inorganic hybrid material: [C7H10NO]2BiBr5

    NASA Astrophysics Data System (ADS)

    Aloui, Z.; Ferretti, V.; Abid, S.; Lefebvre, F.; Rzaigui, M.; Ben Nasr, C.

    2016-08-01

    A novel organic-inorganic hybrid compound, 2-methoxyanilinium pentabromobismuthate(III), [C7H10NO]2BiBr5, was synthesized and its structure determined by means of single crystal X-ray diffraction studies at room temperature. The molecule crystallizes in the orthorhombic C2221 space group with cell parameters a = 11.8870(4), b = 23.4775(8), c = 8.1232(3) Å, V = 2267.0(1) Å3 and four molecules in the unit cell. The structure of the title compound is built up from one-dimensional [BiBr5]2n-n polyanionic zig-zag chains composed of deformed BiBr6 octahedra share Br(2) apex and 2-methoxyanilinium cations. The assignment of the vibrational bands was based on comparison with vibrational mode frequencies of homologous compounds. Theoretical calculations were performed using density functional theory (DFT) for studying the vibrational spectrum of the investigated molecule in its ground state. The 13C CP-MAS NMR spectrum is in agreement with the X-ray structure.

  11. Beyond crystals: the dialectic of materials and information

    PubMed Central

    Cartwright, Julyan H. E.; Mackay, Alan L.

    2012-01-01

    We argue for a convergence of crystallography, materials science and biology, that will come about through asking materials questions about biology and biological questions about materials, illuminated by considerations of information. The complex structures now being studied in biology and produced in nanotechnology have outstripped the framework of classical crystallography, and a variety of organizing concepts are now taking shape into a more modern and dynamic science of structure, form and function. Absolute stability and equilibrium are replaced by metastable structures existing in a flux of energy-carrying information and moving within an energy landscape of complex topology. Structures give place to processes and processes to systems. The fundamental level is that of atoms. As smaller and smaller groups of atoms are used for their physical properties, quantum effects become important; already we see quantum computation taking shape. Concepts move towards those in life with the emergence of specifically informational structures. We now see the possibility of the artificial construction of a synthetic living system, different from biological life, but having many or all of the same properties. Interactions are essentially nonlinear and collective. Structures begin to have an evolutionary history with episodes of symbiosis. Underlying all the structures are constraints of time and space. Through hierarchization, a more general principle than the periodicity of crystals, structures may be found within structures on different scales. We must integrate unifying concepts from dynamical systems and information theory to form a coherent language and science of shape and structure beyond crystals. To this end, we discuss the idea of categorizing structures based on information according to the algorithmic complexity of their assembly. PMID:22615461

  12. Structural Transitions in Cholesteric Liquid Crystal Droplets.

    PubMed

    Zhou, Ye; Bukusoglu, Emre; Martínez-González, José A; Rahimi, Mohammad; Roberts, Tyler F; Zhang, Rui; Wang, Xiaoguang; Abbott, Nicholas L; de Pablo, Juan J

    2016-07-26

    Confinement of cholesteric liquid crystals (ChLC) into droplets leads to a delicate interplay between elasticity, chirality, and surface energy. In this work, we rely on a combination of theory and experiments to understand the rich morphological behavior that arises from that balance. More specifically, a systematic study of micrometer-sized ChLC droplets is presented as a function of chirality and surface energy (or anchoring). With increasing chirality, a continuous transition is observed from a twisted bipolar structure to a radial spherical structure, all within a narrow range of chirality. During such a transition, a bent structure is predicted by simulations and confirmed by experimental observations. Simulations are also able to capture the dynamics of the quenching process observed in experiments. Consistent with published work, it is found that nanoparticles are attracted to defect regions on the surface of the droplets. For weak anchoring conditions at the nanoparticle surface, ChLC droplets adopt a morphology similar to that of the equilibrium helical phase observed for ChLCs in the bulk. As the anchoring strength increases, a planar bipolar structure arises, followed by a morphological transition to a bent structure. The influence of chirality and surface interactions are discussed in the context of the potential use of ChLC droplets as stimuli-responsive materials for reporting molecular adsorbates. PMID:27249186

  13. Crystal structures of MBP fusion proteins.

    PubMed

    Waugh, David S

    2016-03-01

    Although chaperone-assisted protein crystallization remains a comparatively rare undertaking, the number of crystal structures of polypeptides fused to maltose-binding protein (MBP) that have been deposited in the Protein Data Bank (PDB) has grown dramatically during the past decade. Altogether, 102 fusion protein structures were detected by Basic Local Alignment Search Tool (BLAST) analysis. Collectively, these structures comprise a range of sizes, space groups, and resolutions that are typical of the PDB as a whole. While most of these MBP fusion proteins were equipped with short inter-domain linkers to increase their rigidity, fusion proteins with long linkers have also been crystallized. In some cases, surface entropy reduction mutations in MBP appear to have facilitated the formation of crystals. A comparison of the structures of fused and unfused proteins, where both are available, reveals that MBP-mediated structural distortions are very rare. PMID:26682969

  14. Crystal growth, structure analysis and characterisation of 2 - (1, 3 - dioxoisoindolin - 2 - yl) acetic acid single crystal

    SciTech Connect

    Sankari, R. Siva; Perumal, Rajesh Narayana

    2014-04-24

    Single crystal of dielectric material 2 - (1, 3 - dioxoisoindolin - 2 - yl) acetic acid has been grown by slow evaporation solution growth method. The grown crystal was harvested in 25 days. The crystal structure was analyzed by Single crystal X - ray diffraction. UV-vis-NIR analysis was performed to examine the optical property of the grown crystal. The thermal property of the grown crystal was studied by thermogravimetric analysis (TGA) and differential thermal analysis (DTA). The dielectric measurements were carried out and the dielectric constant was calculated and plotted at all frequencies.

  15. Concrete Materials and Structures

    SciTech Connect

    Wilby, C.B.

    1991-12-31

    Concrete Materials and Structures provides one of the most comprehensive treatments on the topic of concrete engineering. The author covers a gamut of concrete subjects ranging from concrete mix design, basic reinforced concrete theory, prestressed concrete, shell roofs, and two-way slabs-including a through presentation of Hillerborg`s strip method. Prior to Wilby`s book, the scope of these topics would require at least four separate books to cover. With this new book he has succeeded, quite remarkably, in condensing a fairly complete knowledge of concrete engineering into one single easy-to-carry volume.

  16. Composite structural materials

    NASA Technical Reports Server (NTRS)

    Loewy, Robert G.; Wiberley, Stephen E.

    1987-01-01

    The development and application of composite materials to aerospace vehicle structures which began in the mid 1960's has now progressed to the point where what can be considered entire airframes are being designed and built using composites. Issues related to the fabrication of non-resin matrix composites and the micro, mezzo and macromechanics of thermoplastic and metal matrix composites are emphasized. Several research efforts are presented. They are entitled: (1) The effects of chemical vapor deposition and thermal treatments on the properties of pitch-based carbon fiber; (2) Inelastic deformation of metal matrix laminates; (3) Analysis of fatigue damage in fibrous MMC laminates; (4) Delamination fracture toughness in thermoplastic matrix composites; (5) Numerical investigation of the microhardness of composite fracture; and (6) General beam theory for composite structures.

  17. Evolution of molecular crystal optical phonons near structural phase transitions

    NASA Astrophysics Data System (ADS)

    Michki, Nigel; Niessen, Katherine; Xu, Mengyang; Markelz, Andrea

    Molecular crystals are increasingly important photonic and electronic materials. For example organic semiconductors are lightweight compared to inorganic semiconductors and have inexpensive scale up processing with roll to roll printing. However their implementation is limited by their environmental sensitivity, in part arising from the weak intermolecular interactions of the crystal. These weak interactions result in optical phonons in the terahertz frequency range. We examine the evolution of intermolecular interactions near structural phase transitions by measuring the optical phonons as a function of temperature and crystal orientation using terahertz time-domain spectroscopy. The measured orientation dependence of the resonances provides an additional constraint for comparison of the observed spectra with the density functional calculations, enabling us to follow specific phonon modes. We observe crystal reorganization near 350 K for oxalic acid as it transforms from dihydrate to anhydrous form. We also report the first THz spectra for the molecular crystal fructose through its melting point.

  18. Crystal structure prediction of rigid molecules.

    PubMed

    Elking, Dennis M; Fusti-Molnar, Laszlo; Nichols, Anthony

    2016-08-01

    A non-polarizable force field based on atomic multipoles fit to reproduce experimental crystal properties and ab initio gas-phase dimers is described. The Ewald method is used to calculate both long-range electrostatic and 1/r(6) dispersion energies of crystals. The dispersion energy of a crystal calculated by a cutoff method is shown to converge slowly to the exact Ewald result. A method for constraining space-group symmetry during unit-cell optimization is derived. Results for locally optimizing 4427 unit cells including volume, cell parameters, unit-cell r.m.s.d. and CPU timings are given for both flexible and rigid molecule optimization. An algorithm for randomly generating rigid molecule crystals is described. Using the correct experimentally determined space group, the average and maximum number of random crystals needed to find the correct experimental structure is given for 2440 rigid single component crystals. The force field energy rank of the correct experimental structure is presented for the same set of 2440 rigid single component crystals assuming the correct space group. A complete crystal prediction is performed for two rigid molecules by searching over the 32 most probable space groups. PMID:27484371

  19. Nanomedicine crystals-inspired optoelectronic device materials and processing

    NASA Astrophysics Data System (ADS)

    Fang, Yan; Wang, Fangzhang; Wu, Rong

    2012-02-01

    Aim: Organic, biological materials and soft matters with optoelectronic donors and acceptors are postulated to be novel optoelectronic device materials. Methods: Molecular self-assemblies of nanomedicine crystals are employed by inelastic electron tunneling interaction force, which is a quantum force to make basic units of organic, biological and soft matter with optoelectronic donors and acceptors to be enlarged from nanometers to micrometers on silicon chips. Results: Self-assembled topographic structures and corresponding conducting with kondo effects and photoluminescence properties of self-assembled nanomedicine crystal building blocks are demonstrated by conducting atomic force microscopy (C-AFM) images and current-voltage curves, and laser micro- photoluminescence (PL) spectra. By contrast to top-down processing, the bottom-up processing of molecular self-assembly is low cost on large scale industrial manufacturing. Conclusion: The self-assembled nanomedicine crystal building blocks with optoelectronic donors and acceptors are candidates of novel optoelectronic device materials to be in the emerging discipline of information technology (IT) in its broadest sense, i.e. bioelectronics & biosensors, optoelectronic devices, data storage devices; simple to complex quantum entanglements and superposition for quantum bits computing, a novel strategy for 2020 IT and beyond.

  20. Nanomedicine crystals-inspired optoelectronic device materials and processing

    NASA Astrophysics Data System (ADS)

    Fang, Yan; Wang, Fangzhang; Wu, Rong

    2011-11-01

    Aim: Organic, biological materials and soft matters with optoelectronic donors and acceptors are postulated to be novel optoelectronic device materials. Methods: Molecular self-assemblies of nanomedicine crystals are employed by inelastic electron tunneling interaction force, which is a quantum force to make basic units of organic, biological and soft matter with optoelectronic donors and acceptors to be enlarged from nanometers to micrometers on silicon chips. Results: Self-assembled topographic structures and corresponding conducting with kondo effects and photoluminescence properties of self-assembled nanomedicine crystal building blocks are demonstrated by conducting atomic force microscopy (C-AFM) images and current-voltage curves, and laser micro- photoluminescence (PL) spectra. By contrast to top-down processing, the bottom-up processing of molecular self-assembly is low cost on large scale industrial manufacturing. Conclusion: The self-assembled nanomedicine crystal building blocks with optoelectronic donors and acceptors are candidates of novel optoelectronic device materials to be in the emerging discipline of information technology (IT) in its broadest sense, i.e. bioelectronics & biosensors, optoelectronic devices, data storage devices; simple to complex quantum entanglements and superposition for quantum bits computing, a novel strategy for 2020 IT and beyond.

  1. Structures of cyano-biphenyl liquid crystals

    NASA Technical Reports Server (NTRS)

    Chu, Yuan-Chao; Tsang, Tung; Rahimzadeh, E.; Yin, L.

    1989-01-01

    The structures of p-alkyl- p'-cyano- bicyclohexanes, C(n)H(2n+1) (C6H10)(C6H10) CN (n-CCH), and p-alkyl- p'-cyano- biphenyls, C(n)H(2n+1) (C6H4)(C6H4) CN (n-CBP), were studied. It is convenient to use an x ray image intensification device to search for symmetric x ray diffraction patterns. Despite the similarities in molecular structures of these compounds, very different crystal structures were found. For the smectic phase of 2CCH, the structure is close to rhombohedral with threefold symmetry. In contrast, the structure is close to hexagonal close-packed with two molecules per unit cell for 4CCH. Since intermolecular forces may be quite weak for these liquid crystals systems, it appears that crystal structures change considerably when the alkyl chain length is slightly altered. Different structures were also found in the crystalline phase of n-CBP for n = 6 to 9. For n = 7 to 9, the structures are close to monclinic. The structures are reminiscent of the smectic-A liquid crystal structures with the linear molecules slightly tilted away from the c-axis. In contrast, the structure is quite different for n = 6 with the molecules nearly perpendicular to the c-axis.

  2. Liquid crystal light valve structures

    NASA Technical Reports Server (NTRS)

    Koda, N. J. (Inventor)

    1985-01-01

    An improved photosensor film and liquid crystal light valves embodying said film is provided. The photosensor film and liquid crystal light valve is characterized by a significant lower image retention time while maintaining acceptable photosensitivity. The photosensor film is produced by sputter depositing CdS onto an ITO substrate in an atmosphere of argon/H2S gas while maintaining the substrate at a temperature in the range of about 130 C to about 200 C and while introducing nitrogen gas into the system to the extent of not more than about 1% of plasma mixture. Following sputter deposition of the CdS, the film is annealed in an inert gas at temperatures ranging from about 300 C to about 425 C.

  3. CuLi{sub 2}Sn and Cu{sub 2}LiSn: Characterization by single crystal XRD and structural discussion towards new anode materials for Li-ion batteries

    SciTech Connect

    Fürtauer, Siegfried; Effenberger, Herta S.; Flandorfer, Hans

    2014-12-15

    The stannides CuLi{sub 2}Sn (CSD-427095) and Cu{sub 2}LiSn (CSD-427096) were synthesized by induction melting of the pure elements and annealing at 400 °C. The phases were reinvestigated by X-ray powder and single-crystal X-ray diffractometry. Within both crystal structures the ordered CuSn and Cu{sub 2}Sn lattices form channels which host Cu and Li atoms at partly mixed occupied positions exhibiting extensive vacancies. For CuLi{sub 2}Sn, the space group F-43m. was verified (structure type CuHg{sub 2}Ti; a=6.295(2) Å; wR{sub 2}(F²)=0.0355 for 78 unique reflections). The 4(c) and 4(d) positions are occupied by Cu atoms and Cu+Li atoms, respectively. For Cu{sub 2}LiSn, the space group P6{sub 3}/mmc was confirmed (structure type InPt{sub 2}Gd; a=4.3022(15) Å, c=7.618(3) Å; wR{sub 2}(F²)=0.060 for 199 unique reflections). The Cu and Li atoms exhibit extensive disorder; they are distributed over the partly occupied positions 2(a), 2(b) and 4(e). Both phases seem to be interesting in terms of application of Cu–Sn alloys as anode materials for Li-ion batteries. - Highlights: • First single crystal investigation of CuLi{sub 2}Sn and Cu{sub 2}LiSn clarifies contradictions from literature. • Lithium atoms are ordered in channels, which is interesting for application as anode materials for lithium ion batteries. • Structural relationships to binary Cu–Sn-phases are shown. • Close structural relationship between both ternary phases exists.

  4. Molecular-Level Understanding of Structural Changes of Organic Crystals Induced by Macroscopic Mechanical Stimulation.

    PubMed

    Seki, Tomohiro; Ito, Hajime

    2016-03-18

    Structural changes to molecular crystals upon mechanical stimulation have attracted attention for sensing, recording, and microactuation. Comprehensive structure information is required to understand relationships between the mechanical force applied, the crystal structure, and the bulk property changes in order to develop general design concepts for mechanoresponsive compounds. Unfortunately, mechanical stimulation of organic crystals typically deteriorates their integrity, preventing detailed structure analyses by single-crystal X-ray diffraction (XRD) methods. However, in the past three years, several interesting studies have been reported in which molecular crystals retain their integrity even after a mechanically induced crystalline structure change. These materials have allowed us to investigate how macroscopic mechanical forces affect the microscopic structures of molecular crystals by single-crystal XRD analyses. This Minireview summarizes current knowledge of mechanically induced structure changes in molecular crystals, which will facilitate research in this field. PMID:26748640

  5. Pholcodine monohydrate: Crystal structure and polymorphism

    NASA Astrophysics Data System (ADS)

    Petruševski, Gjorgji; Zbačnik, Marija; Kajdžanoska, Marina; Ugarkovic, Sonja; Trimčeski, Vase; Kaitner, Branko; Jovanovski, Gligor; Makreski, Petre

    2013-07-01

    The first crystal structure elucidation of pholcodine monohydrate, an important antitussive active pharmaceutical ingredient is reported herein. The studied compound crystallizes in the orthorhombic system in the space group P212121. Each H2O molecule is shared by two pholcodine molecules via three strong hydrogen bonds. The detailed crystallization screening from several different organic solvents afforded single crystals with various quality, all exhibiting prism-to-needlelike micro morphology. The investigation of the obtained single crystals by means of several physico-chemical, solid-state instrumental techniques (FT-IR, DSC, TG/DTG and XRPD) proved that pholcodine monohydrate exists in a single crystalline modification, identical to the commercial form of the compound.

  6. Isotropic behavior of an anisotropic material: single crystal silicon

    NASA Astrophysics Data System (ADS)

    McCarter, Douglas R.; Paquin, Roger A.

    2013-09-01

    Zero defect single crystal silicon (Single-Crystal Si), with its diamond cubic crystal structure, is completely isotropic in most properties important for advanced aerospace systems. This paper will identify behavior of the three most dominant planes of the Single-Crystal Si cube (110), (100) and (111). For example, thermal and optical properties are completely isotropic for any given plane. The elastic and mechanical properties however are direction dependent. But we show through finite element analysis that in spite of this, near-isotropic behavior can be achieved with component designs that utilize the optimum elastic modulus in directions with the highest loads. Using glass frit bonding to assemble these planes is the only bonding agent that doesn't degrade the performance of Single-Crystal Si. The most significant anisotropic property of Single-Crystal Si is the Young's modulus of elasticity. Literature values vary substantially around a value of 145 GPa. The truth is that while the maximum modulus is 185 GPa, the most useful <110< crystallographic direction has a high 169 GPa, still higher than that of many materials such as aluminum and invar. And since Poisson's ratio in this direction is an extremely low 0.064, distortion in the plane normal to the load is insignificant. While the minimum modulus is 130 GPa, a calculated average value is close to the optimum at approximately 160 GPa. The minimum modulus is therefore almost irrelevant. The (111) plane, referred to as the natural cleave plane survives impact that would overload the (110) and/or (100) plane due to its superior density. While mechanical properties vary from plane to plane each plane is uniform and response is predictable. Understanding the Single-Crystal Si diamond cube provides a design and manufacture path for building lightweight Single-Crystal Si systems with near-isotropic response to loads. It is clear then that near-isotropic elastic behavior is achievable in Single-Crystal Si

  7. Method of making macrocrystalline or single crystal semiconductor material

    NASA Technical Reports Server (NTRS)

    Shlichta, P. J. (Inventor); Holliday, R. J. (Inventor)

    1986-01-01

    A macrocrystalline or single crystal semiconductive material is formed from a primary substrate including a single crystal or several very large crystals of a relatively low melting material. This primary substrate is deposited on a base such as steel or ceramic, and it may be formed from such metals as zinc, cadmium, germanium, aluminum, tin, lead, copper, brass, magnesium silicide, or magnesium stannide. These materials generally have a melting point below about 1000 C and form on the base crystals the size of fingernails or greater. The primary substrate has an epitaxial relationship with a subsequently applied layer of material, and because of this epitaxial relationship, the material deposited on the primary substrate will have essentially the same crystal size as the crystals in the primary substrate. If required, successive layers are formed, each of a material which has an epitaxial relationship with the previously deposited layer, until a layer is formed which has an epitaxial relationship with the semiconductive material. This layer is referred to as the epitaxial substrate, and its crystals serve as sites for the growth of large crystals of semiconductive material. The primary substrate is passivated to remove or otherwise convert it into a stable or nonreactive state prior to deposition of the seconductive material.

  8. Structural complexity and configurational entropy of crystals.

    PubMed

    Krivovichev, Sergey V

    2016-04-01

    Using a statistical approach, it is demonstrated that the complexity of a crystal structure measured as the Shannon information per atom [Krivovichev (2012). Acta Cryst. A68, 393-398] represents a negative contribution to the configurational entropy of a crystalline solid. This conclusion is in full accordance with the general agreement that information and entropy are reciprocal variables. It also agrees well with the understanding that complex structures possess lower entropies relative to their simpler counterparts. The obtained equation is consistent with the Landauer principle and points out that the information encoded in a crystal structure has a physical nature. PMID:27048729

  9. Crystal structure of anagyrine perchlorate.

    PubMed

    Turgunov, Kambarali K; Rakhimov, Shukhrat B; Vinogradova, Valentina I; Tashkhodjaev, Bakhodir

    2015-05-01

    The title mol-ecular salt, C15H21N2O(+)·ClO4 (-), crystallizes with four cations (A, B, C and D) and four anions in the chiral unit cell (space group P21). The alkaloid was isolated from the aerial parts of Genista Hispanica collected in the Samarkand region of Uzbekistan. Each cation is protonated at the N atom that bridges the alkaloid rings C and D. In each cation, ring A is almost planar and ring B adops a sofa conformation with the methyl-ene group bridging to the C ring as the flap. Rings C and D adopt chair conformations with a cis ring junction in all four cations. In the crystal, A+B and C+D dimeric pairs linked by pairs of N-H⋯O hydrogen bonds are observed, which generate R 2 (2)(16) loops in each case. The dimers are consolidated by weak aromatic π-π stacking inter-actions between the A rings [centroid-centroid distances = 3.913 (3) and 3.915 (3) Å]. PMID:25995939

  10. Computational studies on the crystal structure, thermodynamic properties, detonation performance, and pyrolysis mechanism of 2,4,6,8-tetranitro-1,3,5,7-tetraazacubane as a novel high energy density material.

    PubMed

    Wang, Fang; Du, Hongchen; Zhang, Jianying; Gong, Xuedong

    2011-10-27

    Studies have suggested that octanitrocubane (ONC) is one of the most powerful non-nuclear high energy density material (HEDM) currently known. 2,4,6,8-Tetranitro-1,3,5,7-tetraazacubane (TNTAC) studied in this work may also be a novel HEDM due to its high nitrogen content and crystal density. Density functional theory and molecular mechanics methods have been employed to study the crystal structure, IR spectrum, electronic structure, thermodynamic properties, gas-phase and condensed-phase heat of formation, detonation performance, and pyrolysis mechanism of TNTAC. The TNTAC has a predicted density of about 2.12 g/cm(3), and its detonation velocity (10.42 km/s) and detonation pressure (52.82 GPa) are higher than that of ONC. The crystalline packing is P2(1)2(1)2(1), and the corresponding cell parameters are Z = 4, a = 8.87 Å, b = 8.87 Å, and c = 11.47 Å. Both the density of states of the predicted crystal and the bond dissociation energy of the molecule in gas phase show that the cage C-N bond is the trigger bond during thermolysis. The activation energy of the pyrolysis initiation reaction obtained from the B3LYP/6-311++G(2df,2p) level is 125.98 kJ/mol, which indicates that TNTAC meets the thermal stability request as an exploitable HEDM. PMID:21919441

  11. Crystal structure of levomepromazine maleate.

    PubMed

    Gál, Gyula Tamás; May, Nóra Veronika; Bombicz, Petra

    2016-05-01

    The asymmetric unit of the title salt, C19H25N2OS(+)·C4H3O4 (-) [systematic name: (S)-3-(2-meth-oxy-pheno-thia-zin-10-yl)-N,N,2-tri-methyl-propanaminium hydrogen maleate], comprises two (S)-levomepromazine cations and two hydrogen maleate anions. The conformations of the two cations are similar. The major difference relates to the orientation of the meth-oxy substituent at the pheno-thia-zine ring system. The crystal components form a three-dimensional supra-molecular network via N-H⋯O, C-H⋯O and C-H⋯π inter-actions. A comparison of the conformations of the levomepromazine cations with those of the neutral mol-ecule and similar protonated mol-ecules reveals significant conformational flexibility of the pheno-thia-zine ring system and the substituent at the pheno-thia-zine N atom. PMID:27308001

  12. Free-Standing Photonic Crystal Films with Gradient Structural Colors.

    PubMed

    Ding, Haibo; Liu, Cihui; Ye, Baofen; Fu, Fanfan; Wang, Huan; Zhao, Yuanjin; Gu, Zhongze

    2016-03-23

    Hydrogel colloidal crystal composite materials have a demonstrated value in responsive photonic crystals (PhCs) via controllable stimuli. Although they have been successfully exploited to generate a gradient of color distribution, the soft hydrogels have limitations in terms of stability and storage caused by dependence on environment. Here, we present a practical strategy to fabricate free-standing PhC films with a stable gradient of structural colors using binary polymer networks. A colloidal crystal hydrogel film was prepared for this purpose, with continuously varying photonic band gaps corresponding to the gradient of the press. Then, a second polymer network was used to lock the inside non-close-packed PhC structures and color distribution of the hydrogel film. It was demonstrated that our strategy could bring about a solution to the angle-dependent structural colors of the PhC films by coating the surface with special microstructures. PMID:26962967

  13. Nucleation and structural growth of cluster crystals.

    PubMed

    Leitold, Christian; Dellago, Christoph

    2016-08-21

    We study the nucleation of crystalline cluster phases in the generalized exponential model with exponent n = 4. Due to the finite value of this pair potential for zero separation, at high densities the system forms cluster crystals with multiply occupied lattice sites. Here, we investigate the microscopic mechanisms that lead to the formation of cluster crystals from a supercooled liquid in the low-temperature region of the phase diagram. Using molecular dynamics and umbrella sampling, we calculate the free energy as a function of the size of the largest crystalline nucleus in the system, and compare our results with predictions from classical nucleation theory. Employing bond-order parameters based on a Voronoi tessellation to distinguish different crystal structures, we analyze the average composition of crystalline nuclei. We find that even for conditions where a multiply occupied fcc crystal is the thermodynamically stable phase, the nucleation into bcc cluster crystals is strongly preferred. Furthermore, we study the particle mobility in the supercooled liquid and in the cluster crystal. In the cluster crystal, the motion of individual particles is captured by a simple reaction-diffusion model introduced previously to model the kinetics of hydrogen bonds. PMID:27544116

  14. Smart materials and structures

    NASA Technical Reports Server (NTRS)

    Rogowski, Robert S.; Heyman, Joseph S.

    1993-01-01

    Embedded optical fibers allow not only the cure-monitoring and in-service lifetime measurements of composite materials, but the NDE of material damage and degradation with aging. The capabilities of such damage-detection systems have been extended to allow the quantitative determination of 2D strain in materials by several different methods, including the interferometric and the numerical. It remains to be seen, what effect the embedded fibers have on the strength of the 'smart' materials created through their incorporation.

  15. Crystal structure of potassium sodium tartrate trihydrate

    SciTech Connect

    Egorova, A. E. Ivanov, V. A.; Somov, N. V.; Portnov, V. N.; Chuprunov, E. V.

    2011-11-15

    Crystals of potassium sodium tartrate trihydrate (dl-KNaC{sub 4}H{sub 4}O{sub 6} {center_dot} 3H{sub 2}O) were obtained from an aqueous solution. The crystal shape was described. The atomic structure of the compound was determined and compared with the known structures of dl-KNaC{sub 4}H{sub 4}O{sub 6} {center_dot} 4H{sub 2}O and l-KNaC{sub 4}H{sub 4}O{sub 6} {center_dot} 4H{sub 2}O.

  16. Crystal structure of canagliflozin hemihydrate.

    PubMed

    Liu, Kai-Hang; Gu, Jian-Ming; Hu, Xiu-Rong; Tang, Gu-Ping

    2016-05-01

    There are two canagliflozin mol-ecules (A and B) and one water mol-ecule in the asymmetric unit of the title compound, C24H25FO5S·0.5H2O [systematic name: (2S,3R,4R,5S,6R)-2-(3-{[5-(4-fluoro-phen-yl)thio-phen-2-yl]meth-yl}-4-methylphen-yl)-6-(hy-droxy-meth-yl)-3,4,5,6-tetra-hydro-2H-pyran-3,4,5-triol hemihydrate]. The dihedral angles between the methyl-benzene and thio-phene rings are 115.7 (4) and 111.7 (4)°, while the dihedral angles between the fluoro-benzene and thio-phene rings are 24.2 (6) and 20.5 (9)° in mol-ecules A and B, respectively. The hydro-pyran ring exhibits a chair conformation in both canagliflozin mol-ecules. In the crystal, the canagliflozin mol-ecules and lattice water mol-ecules are connected via O-H⋯O hydrogen bonds into a three-dimensional supra-molecular architecture. PMID:27308030

  17. Crystal structure of canagliflozin hemihydrate

    PubMed Central

    Liu, Kai-Hang; Gu, Jian-Ming; Hu, Xiu-Rong; Tang, Gu-Ping

    2016-01-01

    There are two canagliflozin mol­ecules (A and B) and one water mol­ecule in the asymmetric unit of the title compound, C24H25FO5S·0.5H2O [systematic name: (2S,3R,4R,5S,6R)-2-(3-{[5-(4-fluoro­phen­yl)thio­phen-2-yl]meth­yl}-4-methylphen­yl)-6-(hy­droxy­meth­yl)-3,4,5,6-tetra­hydro-2H-pyran-3,4,5-triol hemihydrate]. The dihedral angles between the methyl­benzene and thio­phene rings are 115.7 (4) and 111.7 (4)°, while the dihedral angles between the fluoro­benzene and thio­phene rings are 24.2 (6) and 20.5 (9)° in mol­ecules A and B, respectively. The hydro­pyran ring exhibits a chair conformation in both canagliflozin mol­ecules. In the crystal, the canagliflozin mol­ecules and lattice water mol­ecules are connected via O—H⋯O hydrogen bonds into a three-dimensional supra­molecular architecture. PMID:27308030

  18. Crystal structure of levomepromazine maleate

    PubMed Central

    Gál, Gyula Tamás; May, Nóra Veronika; Bombicz, Petra

    2016-01-01

    The asymmetric unit of the title salt, C19H25N2OS+·C4H3O4 − [systematic name: (S)-3-(2-meth­oxy­pheno­thia­zin-10-yl)-N,N,2-tri­methyl­propanaminium hydrogen maleate], comprises two (S)-levomepromazine cations and two hydrogen maleate anions. The conformations of the two cations are similar. The major difference relates to the orientation of the meth­oxy substituent at the pheno­thia­zine ring system. The crystal components form a three-dimensional supra­molecular network via N—H⋯O, C—H⋯O and C—H⋯π inter­actions. A comparison of the conformations of the levomepromazine cations with those of the neutral mol­ecule and similar protonated mol­ecules reveals significant conformational flexibility of the pheno­thia­zine ring system and the substituent at the pheno­thia­zine N atom. PMID:27308001

  19. A terminally protected dipeptide: from crystal structure and self-assembly, through co-assembly with carbon-based materials, to a ternary catalyst for reduction chemistry in water.

    PubMed

    Mazzier, Daniela; Carraro, Francesco; Crisma, Marco; Rancan, Marzio; Toniolo, Claudio; Moretto, Alessandro

    2016-01-01

    A terminally protected, hydrophobic dipeptide Boc-L-Cys(Me)-L-Leu-OMe (1) was synthesized and its 3D-structure was determined by single crystal X-ray diffraction analysis. This peptide is able to hierarchically self-assemble in a variety of superstructures, including hollow rods, ranging from the nano- to the macroscale, and organogels. In addition, 1 is able to drive fullerene (C60) or multiwalled carbon nanotubes (MWCNTs) in an organogel by co-assembling with them. A hybrid 1-C60–MWCNT organogel was prepared and converted (through a high vacuum-drying process) into a robust, high-volume, water insoluble, solid material where C60 is well dispersed over the entire superstructure. This ternary material was successfully tested as a catalyst for: (i) the reduction reaction of water-soluble azo compounds mediated by NaBH4 and UV-light with an overall performance remarkably better than that provided by C60 alone, and (ii) the NaBH4-mediated reduction of benzoic acid to benzyl alcohol. Our results suggest that the self-assembly properties of 1 might be related to the occurrence in its single crystal structure of a sixfold screw axis, a feature shared by most of the linear peptides known so far to give rise to nanotubes. PMID:26463728

  20. Photonic crystal structures with tunable structure color as colorimetric sensors.

    PubMed

    Wang, Hui; Zhang, Ke-Qin

    2013-01-01

    Colorimetric sensing, which transduces environmental changes into visible color changes, provides a simple yet powerful detection mechanism that is well-suited to the development of low-cost and low-power sensors. A new approach in colorimetric sensing exploits the structural color of photonic crystals (PCs) to create environmentally-influenced color-changeable materials. PCs are composed of periodic dielectrics or metallo-dielectric nanostructures that affect the propagation of electromagnetic waves (EM) by defining the allowed and forbidden photonic bands. Simultaneously, an amazing variety of naturally occurring biological systems exhibit iridescent color due to the presence of PC structures throughout multi-dimensional space. In particular, some kinds of the structural colors in living organisms can be reversibly changed in reaction to external stimuli. Based on the lessons learned from natural photonic structures, some specific examples of PCs-based colorimetric sensors are presented in detail to demonstrate their unprecedented potential in practical applications, such as the detections of temperature, pH, ionic species, solvents, vapor, humidity, pressure and biomolecules. The combination of the nanofabrication technique, useful design methodologies inspired by biological systems and colorimetric sensing will lead to substantial developments in low-cost, miniaturized and widely deployable optical sensors. PMID:23539027

  1. Photonic Crystal Structures with Tunable Structure Color as Colorimetric Sensors

    PubMed Central

    Wang, Hui; Zhang, Ke-Qin

    2013-01-01

    Colorimetric sensing, which transduces environmental changes into visible color changes, provides a simple yet powerful detection mechanism that is well-suited to the development of low-cost and low-power sensors. A new approach in colorimetric sensing exploits the structural color of photonic crystals (PCs) to create environmentally-influenced color-changeable materials. PCs are composed of periodic dielectrics or metallo-dielectric nanostructures that affect the propagation of electromagnetic waves (EM) by defining the allowed and forbidden photonic bands. Simultaneously, an amazing variety of naturally occurring biological systems exhibit iridescent color due to the presence of PC structures throughout multi-dimensional space. In particular, some kinds of the structural colors in living organisms can be reversibly changed in reaction to external stimuli. Based on the lessons learned from natural photonic structures, some specific examples of PCs-based colorimetric sensors are presented in detail to demonstrate their unprecedented potential in practical applications, such as the detections of temperature, pH, ionic species, solvents, vapor, humidity, pressure and biomolecules. The combination of the nanofabrication technique, useful design methodologies inspired by biological systems and colorimetric sensing will lead to substantial developments in low-cost, miniaturized and widely deployable optical sensors. PMID:23539027

  2. Computing stoichiometric molecular composition from crystal structures

    PubMed Central

    Gražulis, Saulius; Merkys, Andrius; Vaitkus, Antanas; Okulič-Kazarinas, Mykolas

    2015-01-01

    Crystallographic investigations deliver high-accuracy information about positions of atoms in crystal unit cells. For chemists, however, the structure of a molecule is most often of interest. The structure must thus be reconstructed from crystallographic files using symmetry information and chemical properties of atoms. Most existing algorithms faithfully reconstruct separate molecules but not the overall stoichiometry of the complex present in a crystal. Here, an algorithm that can reconstruct stoichiometrically correct multimolecular ensembles is described. This algorithm uses only the crystal symmetry information for determining molecule numbers and their stoichiometric ratios. The algorithm can be used by chemists and crystallographers as a standalone implementation for investigating above-molecular ensembles or as a function implemented in graphical crystal analysis software. The greatest envisaged benefit of the algorithm, however, is for the users of large crystallographic and chemical databases, since it will permit database maintainers to generate stoichiometrically correct chemical representations of crystal structures automatically and to match them against chemical databases, enabling multidisciplinary searches across multiple databases. PMID:26089747

  3. Structure-property evolution during polymer crystallization

    NASA Astrophysics Data System (ADS)

    Arora, Deepak

    The main theme of this research is to understand the structure-property evolution during crystallization of a semicrystalline thermoplastic polymer. A combination of techniques including rheology, small angle light scattering, differential scanning calorimetry and optical microscopy are applied to follow the mechanical and optical properties along with crystallinity and the morphology. Isothermal crystallization experiments on isotactic poly-1-butene at early stages of spherulite growth provide quantitative information about nucleation density, volume fraction of spherulites and their crystallinity, and the mechanism of connecting into a sample spanning structure. Optical microscopy near the fluid-to-solid transition suggests that the transition, as determined by time-resolved mechanical spectroscopy, is not caused by packing/jamming of spherulites but by the formation of a percolating network structure. The effect of strain, Weissenberg number (We ) and specific mechanical work (w) on rate of crystallization (nucleation followed by growth) and on growth of anisotropy was studied for shear-induced crystallization of isotactic poly-1-butene. The samples were sheared for a finite strain at the beginning of the experiment and then crystallized without further flow (Janeschitz-Kriegl protocol). Strain requirements to attain steady state/leveling off of the rate of crystallization were found to be much larger than the strain needed to achieve steady state of flow. The large strain and We>1 criteria were also observed for morphological transition from spherulitic growth to oriented growth. An apparatus for small angle light scattering (SALS) and light transmission measurements under shear was built and tested at the University of Massachusetts Amherst. As a new development, the polarization direction can be rotated by a liquid crystal polarization rotator (LCPR) with a short response time of 20 ms. The experiments were controlled and analyzed with a LabVIEW(TM) based

  4. Crystal structure of Arabidopsis thaliana cytokinin dehydrogenase

    SciTech Connect

    Bae, Euiyoung; Bingman, Craig A.; Bitto, Eduard; Aceti, David J.; Phillips, Jr., George N.

    2008-08-13

    Since first discovered in Zea mays, cytokinin dehydrogenase (CKX) genes have been identified in many plants including rice and Arabidopsis thaliana, which possesses CKX homologues (AtCKX1-AtCKX7). So far, the three-dimensional structure of only Z. mays CKX (ZmCKX1) has been determined. The crystal structures of ZmCKX1 have been solved in the native state and in complex with reaction products and a slowly reacting substrate. The structures revealed four glycosylated asparagine residues and a histidine residue covalently linked to FAD. Combined with the structural information, recent biochemical analyses of ZmCKX1 concluded that the final products of the reaction, adenine and a side chain aldehyde, are formed by nonenzymatic hydrolytic cleavage of cytokinin imine products resulting directly from CKX catalysis. Here, we report the crystal structure of AtCKX7 (gene locus At5g21482.1, UniProt code Q9FUJ1).

  5. Structural engineering of three-dimensional phononic crystals

    NASA Astrophysics Data System (ADS)

    Delpero, Tommaso; Schoenwald, Stefan; Zemp, Armin; Bergamini, Andrea

    2016-02-01

    Artificially-structured materials are attracting the research interest of a growing community of scientists for the possibility to develop novel materials with advantageous properties that arise from the ability to tailor the propagation of elastic waves, and thus energy, through them. In this work, we propose a three-dimensional phononic crystal whose unit cell has been engineered to obtain a strong wave-attenuation band in the middle of the acoustic frequency range. The combination of its acoustic properties with the dimensions of the unit cell and its static mechanical properties makes it an interesting material for possibly several applications in civil and mechanical engineering, for instance as the core of an acoustically insulating sandwich panel. A sample of this crystal has been manufactured and experimentally tested with respect to its acoustic transmissibility. The performance of the phononic crystal core is remarkable both in terms of amplitude reduction in the transmissibility and width of the attenuation band. A parametric study has been finally conducted on selected geometrical parameters of the unit cell and on their effect on the macroscopic properties of the crystal. This work represents an application-oriented example of how the macroscopic properties of an artificially-structured material can be designed, according to specific needs, by a conventional engineering of its unit cell.

  6. Structural and optical properties of a new chalcone single crystal

    NASA Astrophysics Data System (ADS)

    Rajesh Kumar, P. C.; Ravindrachary, V.; Janardhana, K.; Poojary, Boja

    2012-09-01

    A new nonlinear optical material 1-(4-methylthiophenyl)-3-(4-methoxyphenyl)prop-2-en-1-one with molecular formula C17H16O2S was synthesized by using the Claisen-Schmidt condensation reaction method. The Various functional groups present in the compound were identified using recorded FT-IR spectrum. The crystal growth parameters have been studied using solubility test and acetone is found to be a very good solvent for the crystal growth at an ambient temperature. The transparent high quality single crystals up to a size of 26×2×2 mm3 were grown using the slow evaporation solution growth technique. UV-visible study was carried out and the spectrum reveals that the crystal is transparent in the entire visible region and absorptive in the UV region. The refractive index is determined using Brewster's angle method. The optical energy band gap of the material is measured using Tauc's plot and the direct method. The single crystal XRD of MMPP crystal shows the following cell parameters: a=5.9626(2) Å, b=15.3022(6) Å, c=16.0385(7) Å, α=β=γ=90°, volume=1463.37(10) Å3 with a space group of Pna21. The compound MMPP exhibits optical nonlinearity (NLO) and its second order NLO efficiency is 3.15 times to that of urea. The effect of functional groups OCH3 and SCH3 on the non-linearity as well as the structural property of the compound has been discussed. The crystal is thermally stable. High NLO efficiency, good thermal stability, good transparency and ability to grow as a high quality single crystal make this material very attractive for opto-electronic applications.

  7. Variable temperature study of the crystal and magnetic structures of the giant magnetoresistant materials LMnAsO(L = La, Nd)

    NASA Astrophysics Data System (ADS)

    Emery, N.; Wildman, E. J.; Skakle, J. M. S.; McLaughlin, A. C.; Smith, R. I.; Fitch, A. N.

    2011-04-01

    A variable temperature neutron and synchrotron diffraction study has been performed on the giant magnetoresistant oxypnictides LMnAsO (L = La, Nd). The low-temperature magnetic structures have been studied, and results show a spin reorientation of the Mn2+ spins below TN (Nd) for NdMnAsO. The Mn2+ spins rotate from alignment along c to alignment into the basal plane, and the Mn2+ and Nd3+ moments refine to 3.54(4) μB and 1.93(4) μB, respectively, at 2 K. In contrast, there is no change in magnetic structure with temperature for LaMnAsO. There is no evidence of a structural transition down to 2 K; however, discontinuities in the cell volume and L-O and Mn-As bond lengths are detected at ˜150 K for both materials. This temperature coincides with the electronic transition previously reported and suggests a coupling between electronic and lattice degrees of freedom.

  8. Microstructure and Crystal Structure in TAGS Compositions

    SciTech Connect

    Thompson, A. J.; Sharp, J; Rawn, Claudia J

    2009-01-01

    GeTe, a small bandgap semiconductor that has native p-type defects due to Ge vacancies, is an important constituent in the thermoelectric material known as TAGS. TAGS is an acronym for alloys of GeTe with AgSbTe{sub 2}, and compositions are normally designated as TAGS-x, where x is the fraction of GeTe. TAGS-85 is the most important with regard to applications, and there is also commercial interest in TAGS-80. The crystal structure of GeTe{sub 1+{delta}} has a composition-dependent phase transformation at a temperature ranging from 430 C ({delta} = 0) to {approx}400 C ({delta} = 0.02). The high-temperature form is cubic. The low-temperature form is rhombohedral for {delta} < 0.01, as is the case for good thermoelectric performance. Addition of AgSbTe{sub 2} shifts the phase transformation to lower temperatures, and one of the goals of this work is a systematic study of the dependence of transformation temperature on the parameter x. We present results on phase transformations and associated instabilities in TAGS compositions in the range of 70 at.% to 85 at.% GeTe.

  9. Crystal structure and density of helium to 232 kbar

    NASA Technical Reports Server (NTRS)

    Mao, H. K.; Wu, Y.; Jephcoat, A. P.; Hemley, R. J.; Bell, P. M.; Bassett, W. A.

    1988-01-01

    The properties of helium and hydrogen at high pressure are topics of great interest to the understanding of planetary interiors. These materials constitute 95 percent of the entire solar system. A technique was presented for the measurement of X-ray diffraction from single-crystals of low-Z condenses gases in a diamond-anvil cell at high pressure. The first such single-crystal X-ray diffraction measurements on solid hydrogen to 26.5 GPa were presented. The application of this technique to the problem of the crystal structure, equation of state, and phase diagram of solid helium is reported. Crucial for X-ray diffraction studies of these materials is the use of a synchrotron radiation source which provides high brillance, narrow collimation of the incident and diffracted X-ray beams to reduce the background noise, and energy-dispersive diffraction techniques with polychromatic (white) radiation, which provides high detection efficiency.

  10. Crystal structure and density of helium to 232 kbar

    NASA Astrophysics Data System (ADS)

    Mao, H. K.; Wu, Y.; Jephcoat, A. P.; Hemley, R. J.; Bell, P. M.; Bassett, W. A.

    The properties of helium and hydrogen at high pressure are topics of great interest to the understanding of planetary interiors. These materials constitute 95 percent of the entire solar system. A technique was presented for the measurement of X-ray diffraction from single-crystals of low-Z condenses gases in a diamond-anvil cell at high pressure. The first such single-crystal X-ray diffraction measurements on solid hydrogen to 26.5 GPa were presented. The application of this technique to the problem of the crystal structure, equation of state, and phase diagram of solid helium is reported. Crucial for X-ray diffraction studies of these materials is the use of a synchrotron radiation source which provides high brillance, narrow collimation of the incident and diffracted X-ray beams to reduce the background noise, and energy-dispersive diffraction techniques with polychromatic (white) radiation, which provides high detection efficiency.

  11. Shear induced structures in crystallizing cocoa butter

    NASA Astrophysics Data System (ADS)

    Mazzanti, Gianfranco; Guthrie, Sarah E.; Sirota, Eric B.; Marangoni, Alejandro G.; Idziak, Stefan H. J.

    2004-03-01

    Cocoa butter is the main structural component of chocolate and many cosmetics. It crystallizes in several polymorphs, called phases I to VI. We used Synchrotron X-ray diffraction to study the effect of shear on its crystallization. A previously unreported phase (phase X) was found and a crystallization path through phase IV under shear was observed. Samples were crystallized under shear from the melt in temperature controlled Couette cells, at final crystallization temperatures of 17.5^oC, 20^oC and 22.5^oC in Beamline X10A of NSLS. The formation of phase X was observed at low shear rates (90 s-1) and low crystallization temperature (17.5^oC), but was absent at high shear (720 s-1) and high temperature (20^oC). The d-spacing and melting point suggest that this new phase is a mixture rich on two of the three major components of cocoa butter. We also found that, contrary to previous reports, the transition from phase II to phase V can happen through the intermediate phase IV, at high shear rates and temperature.

  12. Crystal structure of methane oxidation enzyme determined

    SciTech Connect

    Baum, R.

    1994-01-10

    A team of chemists has determined to 2.2-[angstrom] resolution the crystal structure of the hydroxylase protein of methane monooxygenase, the enzyme system responsible for the biological oxidation of methane. The hydroxylase, at a molecular weight of 251,000 daltons, if by far the largest component of methane monooxygenase. Although the crystal structure of the hydroxylase did not reveal any startling surprises about the enzyme-many features of the hydroxylase had been inferred previously from modeling and spectroscopic studies -- obtaining it is a significant achievement. For one thing, the crystal structure unambiguously confirms aspects of the enzyme structure that been at least somewhat speculative. The three-dimensional structure of the enzyme, the chemist say, also provides important insight into biological methane oxidation, including how methane, a relatively inert gas, might diffuse to and bind near the active site of the enzyme. The structure points to particular amino acid residues that are likely to participate in catalysis, and clarifies the structure of the dinuclear iron core of the enzyme.

  13. Crystal structure of monobasic sodium tartrate monohydrate

    SciTech Connect

    Titaeva, E. K. Somov, N. V.; Portnov, V. N.; Titaev, D. N.

    2015-01-15

    Crystals of a new polymorphic modification of monobasic sodium tartrate monohydrate NaHC{sub 4}H{sub 4}O{sub 6} · H{sub 2}O have been grown in a metasilicate gel. Their atomic structure is solved by X-ray diffraction.

  14. Photonic crystal structures for efficent localization or extraction of light

    NASA Astrophysics Data System (ADS)

    Vuckovic, Jelena

    Three-dimensional (3D) photonic crystals offer the opportunity of light manipulation in all directions in space, but they are very difficult to fabricate. On the other hand, planar photonic crystals are much simpler to make, but they exhibit only a "quasi-3D" confinement, resulting from the combined action of 2D photonic crystal and internal reflection. The imperfect confinement in the third dimension produces some unwanted out-of-plane loss, which is usually a limiting factor in performance of these structures. This thesis proposes how to fully take advantage of the relatively simple fabrication of planar photonic crystals, by addressing a problem of loss-reduction. One of the greatest challenges in photonics is a construction of optical microcavities with small mode volumes and large quality factors, for efficient localization of light. Beside standard applications of these structures (such as lasers or filters), they can potentially be used for cavity QED experiments, or as building blocks for quantum networks. This work also presents the design and fabrication of optical microcavities based on planar photonic crystals, with mode volumes of the order of one half of cubic wavelength of light (measured in material) and with Q factors predicted to be even larger than 10 4. In addition to photonic crystals fabricated in semiconductors, we also address interesting properties of metallic photonic crystals and present our theoretical and experimental work on using them to improve the output of light emissive devices. Feature sizes of structures presented here are below those achievable by photolithography. Therefore, a high resolution lithography is necessary for their fabrication. The presently used e-beam writing techniques suffer from limitations in speed and wafer throughput, and they represent a huge obstacle to commercialization of photonic crystals. Our preliminary work on electron beam projection lithography, the technique that could provide us with the speed

  15. Single crystal growth and the electronic structure of orthorhombic Tl3PbBr5: A novel material for non-linear optics

    NASA Astrophysics Data System (ADS)

    Khyzhun, O. Y.; Bekenev, V. L.; Parasyuk, O. V.; Danylchuk, S. P.; Denysyuk, N. M.; Fedorchuk, A. O.; AlZayed, N.; Kityk, I. V.

    2013-03-01

    The X-ray photoelectron core-level and valence-band spectra for pristine and Ar+-ion irradiated surfaces of a Tl3PbBr5 single crystal grown by the Bridgman-Stockbarger method have been measured. The present X-ray photoelectron spectroscopy (XPS) results reveal high chemical stability of Tl3PbBr5 single crystal surface. Total and partial densities of states of constituent atoms of low-temperature (LT) orthorhombic Tl3PbBr5 phase (space group P21212) have been calculated using the full potential linearized augmented plane wave (FP-LAPW) method. The FP-LAPW data reveal that contributions of the Br 4p-like states dominate in the valence band of LT-Tl3PbBr5; they contribute mainly into the top and the central portion of the valence band with also significant contributions throughout the whole valence-band region. The bottom of the valence band of LT-Tl3PbBr5 is composed mainly of the Tl 6s-like states, whilst the unoccupied Pb 6p- and Tl 6p-like states dominate at the bottom of the conduction band. We have explored the crystallochemistry and origin of the chemical bonds in Tl3PbBr5 with respect to the use as mid-IR non-linear optical crystals. Comparison of the spectral dependence to the second order susceptibilities for the titled crystals is performed with respect to the 3.39 μm illuminated crystals. Possibility of the use of Tl3PbBr5 crystals as IR operated non-linear optical crystals is discussed.

  16. Structure analysis on synthetic emerald crystals

    NASA Astrophysics Data System (ADS)

    Lee, Pei-Lun; Lee, Jiann-Shing; Huang, Eugene; Liao, Ju-Hsiou

    2013-05-01

    Single crystals of emerald synthesized by means of the flux method were adopted for crystallographic analyses. Emerald crystals with a wide range of Cr3+-doping content up to 3.16 wt% Cr2O3 were examined by X-ray single crystal diffraction refinement method. The crystal structures of the emerald crystals were refined to R 1 (all data) of 0.019-0.024 and w R 2 (all data) of 0.061-0.073. When Cr3+ substitutes for Al3+, the main adjustment takes place in the Al-octahedron and Be-tetrahedron. The effect of substitution of Cr3+ for Al3+ in the beryl structure results in progressively lengthening of the Al-O distance, while the length of the other bonds remains nearly unchanged. The substitution of Cr3+ for Al3+ may have caused the expansion of a axis, while keeping the c axis unchanged in the emerald lattice. As a consequence, the Al-O-Si and Al-O-Be bonding angles are found to decrease, while the angle of Si-O-Be increases as the Al-O distance increases during the Cr replacement.

  17. Preparation, structural, and calorimetric characterization of bicomponent metallic photonic crystals

    NASA Astrophysics Data System (ADS)

    Kozlov, M. E.; Murthy, N. S.; Udod, I.; Khayrullin, I. I.; Baughman, R. H.; Zakhidov, A. A.

    2007-03-01

    We report preparation and characterization of novel bicomponent metal-based photonic crystals having submicron three-dimensional (3D) periodicity. Fabricated photonic crystals include SiO2 sphere lattices infiltrated interstitially with metals, carbon inverse lattices filled with metal or metal alloy spheres, Sb inverse lattices, and Sb inverse lattices filled with Bi spheres. Starting from a face centered SiO2 lattice template, these materials were obtained by sequences of either templating and template extraction or templating, template extraction, and retemplating. Surprising high fidelity was obtained for all templating and template extraction steps. Scanning electron microscopy (SEM), small angle X-ray scattering (SAXS) and differential scanning calorimetry (DSC) were used to characterize the structure and the effects of the structure on calorimetric properties. To the best of our knowledge, SAXS data on metallic photonic crystals were collected for first time.

  18. Crystal structure of a plectonemic RNA supercoil

    SciTech Connect

    Stagno, Jason R.; Ma, Buyong; Li, Jess; Altieri, Amanda S.; Byrd, R. Andrew; Ji, Xinhua

    2012-12-14

    Genome packaging is an essential housekeeping process in virtually all organisms for proper storage and maintenance of genetic information. Although the extent and mechanisms of packaging vary, the process involves the formation of nucleic-acid superstructures. Crystal structures of DNA coiled coils indicate that their geometries can vary according to sequence and/or the presence of stabilizers such as proteins or small molecules. However, such superstructures have not been revealed for RNA. Here we report the crystal structure of an RNA supercoil, which displays one level higher molecular organization than previously reported structures of DNA coiled coils. In the presence of an RNA-binding protein, two interlocking RNA coiled coils of double-stranded RNA, a 'coil of coiled coils', form a plectonemic supercoil. Molecular dynamics simulations suggest that protein-RNA interaction is required for the stability of the supercoiled RNA. This study provides structural insight into higher order packaging mechanisms of nucleic acids.

  19. Solubility of Structurally Complicated Materials: II. Bone

    NASA Astrophysics Data System (ADS)

    Horvath, Ari L.

    2006-12-01

    Bone is a structurally complex material, formed of both organic and inorganic chemicals. The organic compounds constitute mostly collagen and other proteins. The inorganic or bone mineral components constitute predominantly calcium, phosphate, carbonate, and a host of minor ingredients. The mineralized bone is composed of crystals which are closely associated with a protein of which collagen is an acidic polysaccharide material. This association is very close and the protein integrates into the crystalline structure. The mineralization involves the deposition of relatively insoluble crystals on an organic framework. The solubility process takes place when the outermost ions in the crystal lattice breakaway from the surface and become separated from the crystal. This is characteristic for ions dissolving in water or aqueous solutions at the specified temperature. The magnitude of solubility is temperature and pH dependent. Bone is sparingly soluble in most solvents. Enamel is less soluble than bone and fluoroapatite is the least soluble of all apatites in acid buffers. Collagen is less soluble in neutral salt solution than in dilute acid solutions at ambient temperatures. The solubility of collagens in solvents gradually decreases with increasing age of the bone samples.

  20. Crystal structure of zwitterionic bisimidazolium sulfonates

    NASA Astrophysics Data System (ADS)

    Kohmoto, Shigeo; Okuyama, Shinpei; Yokota, Nobuyuki; Takahashi, Masahiro; Kishikawa, Keiki; Masu, Hyuma; Azumaya, Isao

    2012-05-01

    Crystal structures of three zwitterionic bisimidazolium salts 1-3 in which imidazolium sulfonate moieties were connected with aromatic linkers, p-xylylene, 4,4'-dimethylenebiphenyl, and phenylene, respectively, were examined. The latter two were obtained as hydrates. An S-shaped molecular structure in which the sulfonate moiety was placed on the imidazolium ring was observed for 1. A helical array of hydrated water molecules was obtained for 2 while a linear array of hydrated water molecules was observed for 3.

  1. Crystal Structure of Human Enterovirus 71

    SciTech Connect

    Plevka, Pavel; Perera, Rushika; Cardosa, Jane; Kuhn, Richard J.; Rossmann, Michael G.

    2013-04-08

    Enterovirus 71 is a picornavirus associated with fatal neurological illness in infants and young children. Here, we report the crystal structure of enterovirus 71 and show that, unlike in other enteroviruses, the 'pocket factor,' a small molecule that stabilizes the virus, is partly exposed on the floor of the 'canyon.' Thus, the structure of antiviral compounds may require a hydrophilic head group designed to interact with residues at the entrance of the pocket.

  2. On calculating the equilibrium structure of molecular crystals.

    SciTech Connect

    Mattsson, Ann Elisabet; Wixom, Ryan R.; Mattsson, Thomas Kjell Rene

    2010-03-01

    The difficulty of calculating the ambient properties of molecular crystals, such as the explosive PETN, has long hampered much needed computational investigations of these materials. One reason for the shortcomings is that the exchange-correlation functionals available for Density Functional Theory (DFT) based calculations do not correctly describe the weak intermolecular van der Waals' forces present in molecular crystals. However, this weak interaction also poses other challenges for the computational schemes used. We will discuss these issues in the context of calculations of lattice constants and structure of PETN with a number of different functionals, and also discuss if these limitations can be circumvented for studies at non-ambient conditions.

  3. Structural, magnetic and optical properties of two concomitant molecular crystals

    NASA Astrophysics Data System (ADS)

    Silva, Manuela Ramos; Milne, Bruce; Coutinho, Joana T.; Pereira, Laura C. J.; Martín-Ramos, Pablo; Pereira da Silva, Pedro S.; Martín-Gil, Jesús

    2016-03-01

    A new 1D complex has been prepared and characterized. X-ray single crystal structure confirms that the Cu(II) ions assemble in alternating chains with Cu … Cu distances of 2.5685(4) and 3.1760(4) Å. The temperature dependence of the magnetic susceptibility reveals an antiferromagnetic interaction between the paddle-wheel copper centers with an exchange of -300 cm-1. The exchange integral was also determined by quantum chemical ab-initio calculations, using polarised and unpolarised basis sets reproducing well the experimental value. The second harmonic generation efficiency of a concomitantly crystallized material was evaluated and was found to be comparable to urea.

  4. Benzen and Ethylene Binding to Copper(I)-Ziconium(IV) Chloride Materials: The Crystal Structure and Solid-State Reactivity of ((bz)2Cu)2Zr2Cl10.bz

    SciTech Connect

    Dattelbaum,A.; Martin, J.

    2006-01-01

    The solvothermal reaction of Cu{sub 2}ZrCl{sub 6} and ZrCl{sub 4} in benzene is shown to yield the molecular species ((bz){sub 2}Cu){sub 2}Zr{sub 2}Cl{sub 10} {center_dot} bz(1), which is characterized by single crystal X-ray diffraction. The structure consists of edge-shared dimers of zirconium chloride octahedra whose axial chlorides are bridged by bis-benzene chlorocuprate fragments. The Cu{sub 2}Zr{sub 2} tetramers are linked in the crystal lattice by edge-to-face {pi}-stacking of the coordinated and lattice benzene molecules, as well as benzene-to-chloride hydrogen bonding. Benzene is lost from this material in a stepwise fashion resulting in what are described to be chain, ((bz)Cu){sub 2}Zr{sub 2}Cl{sub 10} (3). The desolvated materials, 2 and 3, reversibly sorb ethylene, as characterized by sorption isotherms, in situ pressure-resolved synchrotron X-ray diffraction and UV/Vis diffuse reflectance spectroscopy.

  5. Synthesis, crystal growth, structural, thermal, optical and mechanical properties of solution grown 4-methylpyridinium 4-hydroxybenzoate single crystal.

    PubMed

    Sudhahar, S; Krishna Kumar, M; Sornamurthy, B M; Mohan Kumar, R

    2014-01-24

    Organic nonlinear optical material, 4-methylpyridinium 4-hydroxybenzoate (4MPHB) was synthesized and single crystal was grown by slow evaporation solution growth method. Single crystal and powder X-ray diffraction analyses confirm the structure and crystalline perfection of 4MPHB crystal. Infrared, Raman and NMR spectroscopy techniques were used to elucidate the functional groups present in the compound. TG-DTA analysis was carried out in nitrogen atmosphere to study the decomposition stages, endothermic and exothermic reactions. UV-visible and Photoluminescence spectra were recorded for the grown crystal to estimate the transmittance and band gap energy respectively. Linear refractive index, birefringence, and SHG efficiency of the grown crystal were studied. Laser induced surface damage threshold and mechanical properties of grown crystal were studied to assess the suitability of the grown crystals for device applications. PMID:24184578

  6. Methods of using structures including catalytic materials disposed within porous zeolite materials to synthesize hydrocarbons

    DOEpatents

    Rollins, Harry W.; Petkovic, Lucia M.; Ginosar, Daniel M.

    2011-02-01

    Catalytic structures include a catalytic material disposed within a zeolite material. The catalytic material may be capable of catalyzing a formation of methanol from carbon monoxide and/or carbon dioxide, and the zeolite material may be capable of catalyzing a formation of hydrocarbon molecules from methanol. The catalytic material may include copper and zinc oxide. The zeolite material may include a first plurality of pores substantially defined by a crystal structure of the zeolite material and a second plurality of pores dispersed throughout the zeolite material. Systems for synthesizing hydrocarbon molecules also include catalytic structures. Methods for synthesizing hydrocarbon molecules include contacting hydrogen and at least one of carbon monoxide and carbon dioxide with such catalytic structures. Catalytic structures are fabricated by forming a zeolite material at least partially around a template structure, removing the template structure, and introducing a catalytic material into the zeolite material.

  7. Crystal structure of riboflavin synthase

    SciTech Connect

    Liao, D.-I.; Wawrzak, Z.; Calabrese, J.C.; Viitanen, P.V.; Jordan, D.B.

    2010-03-05

    Riboflavin synthase catalyzes the dismutation of two molecules of 6,7-dimethyl-8-(1'-D-ribityl)-lumazine to yield riboflavin and 4-ribitylamino-5-amino-2,6-dihydroxypyrimidine. The homotrimer of 23 kDa subunits has no cofactor requirements for catalysis. The enzyme is nonexistent in humans and is an attractive target for antimicrobial agents of organisms whose pathogenicity depends on their ability to biosynthesize riboflavin. The first three-dimensional structure of the enzyme was determined at 2.0 {angstrom} resolution using the multiwavelength anomalous diffraction (MAD) method on the Escherichia coli protein containing selenomethionine residues. The homotrimer consists of an asymmetric assembly of monomers, each of which comprises two similar {beta} barrels and a C-terminal {alpha} helix. The similar {beta} barrels within the monomer confirm a prediction of pseudo two-fold symmetry that is inferred from the sequence similarity between the two halves of the protein. The {beta} barrels closely resemble folds found in phthalate dioxygenase reductase and other flavoproteins. The three active sites of the trimer are proposed to lie between pairs of monomers in which residues conserved among species reside, including two Asp-His-Ser triads and dyads of Cys-Ser and His-Thr. The proposed active sites are located where FMN (an analog of riboflavin) is modeled from an overlay of the {beta} barrels of phthalate dioxygenase reductase and riboflavin synthase. In the trimer, one active site is formed, and the other two active sites are wide open and exposed to solvent. The nature of the trimer configuration suggests that only one active site can be formed and be catalytically competent at a time.

  8. Absorption enhancement in graphene photonic crystal structures.

    PubMed

    Khaleque, Abdul; Hattori, Haroldo T

    2016-04-10

    Graphene, a single layer of carbon atoms arranged in a honeycomb lattice, is attracting significant interest because of its potential applications in electronic and optoelectronic devices. Although graphene exhibits almost uniform absorption within a large wavelength range, its interaction with light is weak. In this paper, the enhancement of the optical absorption in graphene photonic crystal structures is studied: the structure is modified by introducing scatterers and mirrors. It is shown that the absorption of the graphene photonic crystal structure can be enhanced about four times (nearly 40%) with respect to initial reference absorption of 9.8%. The study can be a useful tool for investigating graphene physics in different optical settings. PMID:27139857

  9. Crystal structure of low-symmetry rondorfite

    SciTech Connect

    Rastsvetaeva, R. K. Zadov, A. E.; Chukanov, N. V.

    2008-03-15

    The crystal structure of an aluminum-rich variety of the mineral rondorfite with the composition Ca{sub 16}[Mg{sub 2}(Si{sub 7}Al)(O{sub 31}OH)]Cl{sub 4} from the skarns of the Verkhne-Chegemskoe plateau (the Kabardino-Balkarian Republic, the Northern Caucasus Region, Russia) was solved in the triclinic space group with the unit-cell parameters a = 15.100(2) A, b = 15.110(2) A, c = 15.092(2) A, {alpha} = 90.06(1) deg., {beta} = 90.01(1) deg., {gamma} = 89.93(1) deg., Z = 4, sp. gr. P1. The structural model consisting of 248 independent atoms was determined by the phase-correction method and refined to R = 3.8% with anisotropic displacement parameters based on all 7156 independent reflections with 7156 F > 3{sigma}(F). The crystal structure is based on pentamers consisting of four Si tetrahedra linked by the central Mg tetrahedron. The structure can formally be refined in the cubic space group (a = 15.105 A, sp. gr. Fd-bar 3, seven independent positions) with anisotropic displacement parameters to R = 2.74% based on 579 reflections with F > 3{sigma}(F) without accounting for more than 1000 observed reflections, which are inconsistent with the cubic symmetry of the crystal structure.

  10. Crystal structure of low-symmetry rondorfite

    SciTech Connect

    Rastsvetaeva, R. K.; Zadov, A. E.; Chukanov, N. V.

    2008-03-15

    The crystal structure of an aluminum-rich variety of the mineral rondorfite with the composition Ca{sub 16}[Mg{sub 2}(Si{sub 7}Al)(O{sub 31}OH)]Cl{sub 4} from the skarns of the Verkhne-Chegemskoe plateau (the Kabardino-Balkarian Republic, the Northern Caucasus Region, Russia) was solved in the triclinic space group with the unit-cell parameters a = 15.100(2) Angstrom-Sign , b = 15.110(2) Angstrom-Sign , c = 15.092(2) Angstrom-Sign , {alpha} = 90.06(1) Degree-Sign , {beta} = 90.01(1) Degree-Sign , {gamma} = 89.93(1) Degree-Sign , Z = 4, sp. gr. P1. The structural model consisting of 248 independent atoms was determined by the phase-correction method and refined to R = 3.8% with anisotropic displacement parameters based on all 7156 independent reflections with 7156 F > 3{sigma}(F). The crystal structure is based on pentamers consisting of four Si tetrahedra linked by the central Mg tetrahedron. The structure can formally be refined in the cubic space group (a = 15.105 Angstrom-Sign , sp. gr. Fd 3 bar , seven independent positions) with anisotropic displacement parameters to R = 2.74% based on 579 reflections with F > 3{sigma}(F) without accounting for more than 1000 observed reflections, which are inconsistent with the cubic symmetry of the crystal structure.

  11. Can antimonide-based nanowires form wurtzite crystal structure?

    NASA Astrophysics Data System (ADS)

    Gorji Ghalamestani, Sepideh; Lehmann, Sebastian; Dick, Kimberly A.

    2016-01-01

    The epitaxial growth of antimonide-based nanowires has become an attractive subject due to their interesting properties required for various applications such as long-wavelength IR detectors. The studies conducted on antimonide-based nanowires indicate that they preferentially crystallize in the zinc blende (ZB) crystal structure rather than wurtzite (WZ), which is common in other III-V nanowire materials. Also, with the addition of small amounts of antimony to arsenide- and phosphide-based nanowires grown under conditions otherwise leading to WZ structure, the crystal structure of the resulting ternary nanowires favors the ZB phase. Therefore, the formation of antimonide-based nanowires with the WZ phase presents fundamental challenges and is yet to be explored, but is particularly interesting for understanding the nanowire crystal phase in general. In this study, we examine the formation of Au-seeded InSb and GaSb nanowires under various growth conditions using metalorganic vapor phase epitaxy. We address the possibility of forming other phases than ZB such as WZ and 4H in binary nanowires and demonstrate the controlled formation of WZ InSb nanowires. We further discuss the fundamental aspects of WZ growth in Au-seeded antimonide-based nanowires.The epitaxial growth of antimonide-based nanowires has become an attractive subject due to their interesting properties required for various applications such as long-wavelength IR detectors. The studies conducted on antimonide-based nanowires indicate that they preferentially crystallize in the zinc blende (ZB) crystal structure rather than wurtzite (WZ), which is common in other III-V nanowire materials. Also, with the addition of small amounts of antimony to arsenide- and phosphide-based nanowires grown under conditions otherwise leading to WZ structure, the crystal structure of the resulting ternary nanowires favors the ZB phase. Therefore, the formation of antimonide-based nanowires with the WZ phase presents

  12. Persistent hydrogen bonding in polymorphic crystal structures.

    PubMed

    Galek, Peter T A; Fábián, László; Allen, Frank H

    2009-02-01

    The significance of hydrogen bonding and its variability in polymorphic crystal structures is explored using new automated structural analysis methods. The concept of a chemically equivalent hydrogen bond is defined, which may be identified in pairs of structures, revealing those types of bonds that may persist, or not, in moving from one polymorphic form to another. Their frequency and nature are investigated in 882 polymorphic structures from the Cambridge Structural Database. A new method to compare conformations of equivalent molecules is introduced and applied to derive distinct subsets of conformational and packing polymorphs. The roles of chemical functionality and hydrogen-bond geometry in persistent interactions are systematically explored. Detailed structural comparisons reveal a large majority of persistent hydrogen bonds that are energetically crucial to structural stability. PMID:19155561

  13. Composite structural materials

    NASA Technical Reports Server (NTRS)

    Ansell, G. S.; Loewy, R. G.; Wiberley, S. E.

    1983-01-01

    Transverse properties of fiber constituents in composites, fatigue in composite materials, matrix dominated properties of high performance composites, numerical investigation of moisture effects, numerical investigation of the micromechanics of composite fracture, advanced analysis methods, compact lug design, and the RP-1 and RP-2 sailplanes projects are discussed.

  14. Crystal structure of laser-induced subsurface modifications in Si

    SciTech Connect

    Verburg, P. C.; Smillie, L. A.; Römer, G. R. B. E.; Haberl, B.; Bradby, J. E.; Williams, J. S.; Huis in ’t Veld, A. J.

    2015-06-04

    Laser-induced subsurface modification of dielectric materials is a well-known technology. Applications include the production of optical components and selective etching. In addition to dielectric materials, the subsurface modification technology can be applied to silicon, by employing near to mid-infrared radiation. An application of subsurface modifications in silicon is laser-induced subsurface separation, which is a method to separate wafers into individual dies. Other applications for which proofs of concept exist are the formation of waveguides and resistivity tuning. However, limited knowledge is available about the crystal structure of subsurface modifications in silicon. In this paper, we investigate the geometry and crystal structure of laser-induced subsurface modifications in monocrystalline silicon wafers. Finally, in addition to the generation of lattice defects, we found that transformations to amorphous silicon and Si-iii/Si-xii occur as a result of the laser irradiation.

  15. Thermoelectric Materials With the Skutterudite Structure: New Results

    NASA Technical Reports Server (NTRS)

    Fleurial, J. -P.; Caillat, T.; Borshchevsky, A.

    1995-01-01

    New experimental findings on semiconductors with the relatively complex 32 atom unit cell skutterudite crystal structure show that these materials possess attractive transport properties and have a good potential for achieving ZT values larger than for state-of- the-art thermoelectric materials. An overview of recent results is provided, and current approaches to experimentally achieving high ZT in skutterudite materials are discussed.

  16. Visible stealth materials based on photonic crystals

    NASA Astrophysics Data System (ADS)

    Yao, Guozheng; Liu, Ying

    2014-08-01

    Optical thin film can be used for invisible cloak. As a kind of low-dimension photonic crystal, it is a candidate for metamaterial with designed Σ and μ. As a coating, it is convenient to be stacked to mimic continuous changing of electromagnetic media. Anti-reflection film is suitable for matching coating between layers of media.

  17. The Incorporation of C in the Crystal Lattice of Metals; Its Role on the Structure and Properties of these New Materials Called Covetics

    NASA Astrophysics Data System (ADS)

    Salamanca-Riba, Lourdes; Isaacs, Romaine; Forrest, David; Mansour, Azzam; Herzing, Andrew; Lemieux, Melburne; Shugart, Jason

    2013-03-01

    Nanocarbon has been successfully incorporated in molten metals and metal alloys using a new method of manufacturing in which the molten metal (or metal alloy) acts as ionizing medium causing nanocarbon structures to form in-situ. C in concentrations up to ~10% weight was incorporated in Ag, Al and Cu. The bonding between the carbon and the metal is very strong and persists after re-melting and resolidification. These materials, called ``covetics,'' show improved properties over those of the host metal. For example, the thermal conductivity of Cu covetic is higher than pure Cu. The electrical conductivity of Al covetic is higher than for pure Al. The yield strength of Al and Cu covetics is higher than the pure metals. We have used X-ray diffraction, X-ray photoelectron spectroscopy, and Raman spectroscopy to investigate the incorporation of C in the metal. Scanning and transmission electron microscopy (TEM) were also employed along with energy dispersive X-ray spectroscopy and electron energy loss spectroscopy (EELS). The nanocarbons in the covetics are in the form of, graphene nanoribbons, and amorphous nanocarbon, and all are bonded to the metal. The C-K edge in the EELS, and the Raman spectra from these samples show signals characteristic of graphitic sp2 bonding. Supported in part by NSF MRSEC DMR 0520471 and ONR Code 332 # N0001410WX20992.

  18. Studies on synthesis, growth, structural, optical properties of organic 8-hydroxyquinolinium succinate single crystals

    SciTech Connect

    Thirumurugan, R. Anitha, K.

    2014-04-24

    8-hydroxyquinolinium succinate (8HQSU), an organic material has been synthesized and single crystals were grown by employing the technique of slow evaporation. The structure of the grown crystal was elucidated by using single crystal X-ray diffraction analysis. 8HQSU crystal belongs to the monoclinic crystallographic system with non-centro symmetric space group of P2{sub 1}. FT-IR spectral investigation has been carried out to identify the various functional groups present in the grown crystal. UV–vis spectral studies reveal that 8HQSU crystals are transparent in the entire visible region and the cut-off wavelength has been found to be 220nm.

  19. Studies on synthesis, growth, structural, optical properties of organic 8-hydroxyquinolinium succinate single crystals

    NASA Astrophysics Data System (ADS)

    Thirumurugan, R.; Anitha, K.

    2014-04-01

    8-hydroxyquinolinium succinate (8HQSU), an organic material has been synthesized and single crystals were grown by employing the technique of slow evaporation. The structure of the grown crystal was elucidated by using single crystal X-ray diffraction analysis. 8HQSU crystal belongs to the monoclinic crystallographic system with non-centro symmetric space group of P21. FT-IR spectral investigation has been carried out to identify the various functional groups present in the grown crystal. UV-vis spectral studies reveal that 8HQSU crystals are transparent in the entire visible region and the cut-off wavelength has been found to be 220nm.

  20. Synthesis and Crystal Structure of Gold Nanobelts

    PubMed Central

    2015-01-01

    Gold nanobelts were synthesized by the reduction of tetrachloroauric acid with ascorbic acid in the presence of the surfactants cetyltrimethylammonium bromide and sodium dodecylsulfate. The resulting structures have rectangular cross sectional dimensions that are tens of nanometers and lengths that are tens to hundreds of micrometers. We find that the nanobelt yield and resulting structures are very sensitive to temperature which is likely due to the transition of the surfactant solution from wormlike micelles to spherical micelles. The nanobelt crystal structure contains a mixture of face centered cubic and hexagonally close packed lattice phases that can be isolated and examined individually due to the unique nanobelt size and shape. PMID:24803725

  1. Composite structural materials

    NASA Technical Reports Server (NTRS)

    Ansell, G. S.; Loewy, R. G.; Wiberley, S. E.

    1981-01-01

    The composite aircraft program component (CAPCOMP) is a graduate level project conducted in parallel with a composite structures program. The composite aircraft program glider (CAPGLIDE) is an undergraduate demonstration project which has as its objectives the design, fabrication, and testing of a foot launched ultralight glider using composite structures. The objective of the computer aided design (COMPAD) portion of the composites project is to provide computer tools for the analysis and design of composite structures. The major thrust of COMPAD is in the finite element area with effort directed at implementing finite element analysis capabilities and developing interactive graphics preprocessing and postprocessing capabilities. The criteria for selecting research projects to be conducted under the innovative and supporting research (INSURE) program are described.

  2. Coagulation factor XII protease domain crystal structure

    PubMed Central

    Pathak, M; Wilmann, P; Awford, J; Li, C; Hamad, BK; Fischer, PM; Dreveny, I; Dekker, LV; Emsley, J

    2015-01-01

    Background Coagulation factor XII is a serine protease that is important for kinin generation and blood coagulation, cleaving the substrates plasma kallikrein and FXI. Objective To investigate FXII zymogen activation and substrate recognition by determining the crystal structure of the FXII protease domain. Methods and results A series of recombinant FXII protease constructs were characterized by measurement of cleavage of chromogenic peptide and plasma kallikrein protein substrates. This revealed that the FXII protease construct spanning the light chain has unexpectedly weak proteolytic activity compared to β-FXIIa, which has an additional nine amino acid remnant of the heavy chain present. Consistent with these data, the crystal structure of the light chain protease reveals a zymogen conformation for active site residues Gly193 and Ser195, where the oxyanion hole is absent. The Asp194 side chain salt bridge to Arg73 constitutes an atypical conformation of the 70-loop. In one crystal form, the S1 pocket loops are partially flexible, which is typical of a zymogen. In a second crystal form of the deglycosylated light chain, the S1 pocket loops are ordered, and a short α-helix in the 180-loop of the structure results in an enlarged and distorted S1 pocket with a buried conformation of Asp189, which is critical for P1 Arg substrate recognition. The FXII structures define patches of negative charge surrounding the active site cleft that may be critical for interactions with inhibitors and substrates. Conclusions These data provide the first structural basis for understanding FXII substrate recognition and zymogen activation. PMID:25604127

  3. Confined Crystals of the Smallest Phase-Change Material

    PubMed Central

    2013-01-01

    The demand for high-density memory in tandem with limitations imposed by the minimum feature size of current storage devices has created a need for new materials that can store information in smaller volumes than currently possible. Successfully employed in commercial optical data storage products, phase-change materials, that can reversibly and rapidly change from an amorphous phase to a crystalline phase when subject to heating or cooling have been identified for the development of the next generation electronic memories. There are limitations to the miniaturization of these devices due to current synthesis and theoretical considerations that place a lower limit of 2 nm on the minimum bit size, below which the material does not transform in the structural phase. We show here that by using carbon nanotubes of less than 2 nm diameter as templates phase-change nanowires confined to their smallest conceivable scale are obtained. Contrary to previous experimental evidence and theoretical expectations, the nanowires are found to crystallize at this scale and display amorphous-to-crystalline phase changes, fulfilling an important prerequisite of a memory element. We show evidence for the smallest phase-change material, extending thus the size limit to explore phase-change memory devices at extreme scales. PMID:23984706

  4. Photonic crystal and photonic wire device structures

    NASA Astrophysics Data System (ADS)

    De La Rue, Richard; Sorel, Marc; Johnson, Nigel; Rahman, Faiz; Ironside, Charles; Cronin, Lee; Watson, Ian; Martin, Robert; Jin, Chongjun; Pottier, Pierre; Chong, Harold; Gnan, Marco; Jugessur, Aju; Camargo, Edilson; Erwin, Grant; Md Zain, Ahmad; Ntakis, Iraklis; Hobbs, Lois; Zhang, Hua; Armenise, Mario; Ciminelli, Caterina; Coquillat, Dominique

    2005-09-01

    Photonic devices that exploit photonic crystal (PhC) principles in a planar environment continue to provide a fertile field of research. 2D PhC based channel waveguides can provide both strong confinement and controlled dispersion behaviour. In conjunction with, for instance, various electro-optic, thermo-optic and other effects, a range of device functionality is accessible in very compact PhC channel-guide devices that offer the potential for high-density integration. Low enough propagation losses are now being obtained with photonic crystal channel-guide structures that their use in real applications has become plausible. Photonic wires (PhWs) can also provide strong confinement and low propagation losses. Bragg-gratings imposed on photonic wires can provide dispersion and frequency selection in device structures that are intrinsically simpler than 2D PhC channel guides--and can compete with them under realistic conditions.

  5. Synthesis, crystal growth and characterization of an organic material: 2-Aminopyridinium succinate succinic acid single crystal.

    PubMed

    Magesh, M; Bhagavannarayana, G; Ramasamy, P

    2015-11-01

    The 2-aminopyridinium succinate succinic acid (2APS) single crystal was synthesized and grown by slow evaporation method. The crystal structure has been confirmed by powder X-ray diffraction as well as single crystal X-ray diffraction analysis. The crystal perfection has been evaluated by high resolution X-ray diffraction (HRXRD). The grown crystal is transparent in the visible and near infrared region. The optical absorption edge was found to be 348 nm. The fluorescence study was carried out by spectrofluorophotometer. The thermal stability of grown crystal was analyzed by thermal gravimetric and differential thermal gravimetric (TG-DTA) analysis. Vicker's hardness study carried out at room temperature shows increased hardness while increasing the load. Laser damage threshold value was determined by Nd:YAG laser operating at 1064 nm. The grown 2APS crystal was characterized by etching studies using water as etchant. PMID:26099828

  6. Composite structural materials

    NASA Technical Reports Server (NTRS)

    Ansell, G. S.; Loewy, R. G.; Wiberley, S. E.

    1983-01-01

    Progress and plans are reported for investigations of: (1) the mechanical properties of high performance carbon fibers; (2) fatigue in composite materials; (3) moisture and temperature effects on the mechanical properties of graphite-epoxy laminates; (4) the theory of inhomogeneous swelling in epoxy resin; (5) numerical studies of the micromechanics of composite fracture; (6) free edge failures of composite laminates; (7) analysis of unbalanced laminates; (8) compact lug design; (9) quantification of Saint-Venant's principles for a general prismatic member; (10) variation of resin properties through the thickness of cured samples; and (11) the wing fuselage ensemble of the RP-1 and RP-2 sailplanes.

  7. Composite structural materials

    NASA Technical Reports Server (NTRS)

    Loewy, Robert G.; Wiberley, Stephen E.

    1988-01-01

    A decade long program to develop critical advanced composite technology in the areas of physical properties, structural concept and analysis, manufacturing, reliability, and life predictions is reviewed. Specific goals are discussed. The status of the chemical vapor deposition effects on carbon fiber properties; inelastic deformation of metal matrix laminates; fatigue damage in fibrous MMC laminates; delamination fracture toughness in thermoplastic matrix composites; and numerical analysis of composite micromechanical behavior are presented.

  8. Observations on the crystal structures of lueshite

    NASA Astrophysics Data System (ADS)

    Mitchell, Roger H.; Burns, Peter C.; Knight, Kevin S.; Howard, Christopher J.; Chakhmouradian, Anton R.

    2014-06-01

    Laboratory powder XRD patterns of the perovskite-group mineral lueshite from the type locality (Lueshe, Kivu, DRC) and pure NaNbO3 demonstrate that lueshite does not adopt the same space group ( Pbma; #57) as the synthetic compound. The crystal structures of lueshite (2 samples) from Lueshe, Mont Saint-Hilaire (Quebec, Canada) and Sallanlatvi (Kola, Russia) have been determined by single-crystal CCD X-ray diffraction. These room temperature X-ray data for all single-crystal samples can be satisfactorily refined in the orthorhombic space group Pbnm (#62). Cell dimensions, atomic coordinates of the atoms, bond lengths and octahedron tilt angles are given for four crystals. Conventional neutron diffraction patterns for Lueshe lueshite recorded over the temperature range 11-1,000 K confirm that lueshite does not adopt space group Pbma within these temperatures. Neutron diffraction indicates no phase changes on cooling from room temperature to 11 K. None of these neutron diffraction data give satisfactorily refinements but suggest that this is the space group Pbnm. Time-of-flight neutron diffraction patterns for Lueshe lueshite recorded from room temperature to 700 °C demonstrate phase transitions above 550 °C from Cmcm through P4 /mbm to above 650 °C. Cell dimensions and atomic coordinates of the atoms are given for the three high-temperature phases. The room temperature to 400 °C structures cannot be satisfactorily resolved, and it is suggested that the lueshite at room temperature consists of domains of pinned metastable phases with orthorhombic and/or monoclinic structures. However, the sequence of high-temperature phase transitions observed is similar to those determined for synthetic NaTaO3, suggesting that the equilibrated room temperature structure of lueshite is orthorhombic Pbnm.

  9. Crystal Structures of New Ammonium 5-Aminotetrazolates

    PubMed Central

    Lampl, Martin; Salchner, Robert; Laus, Gerhard; Braun, Doris E.; Kahlenberg, Volker; Wurst, Klaus; Fuhrmann, Gerda; Schottenberger, Herwig; Huppertz, Hubert

    2015-01-01

    The crystal structures of three salts of anionic 5-aminotetrazole are described. The tetramethylammonium salt (P1‒) forms hydrogen-bonded ribbons of anions which accept weak C–H⋯N contacts from the cations. The cystamine salt (C2/c) shows wave-shaped ribbons of anions linked by hydrogen bonds to screw-shaped dications. The tetramethylguanidine salt (P21/c) exhibits layers of anions hydrogen-bonded to the cations. PMID:26753100

  10. Hypersonic Materials and Structures

    NASA Technical Reports Server (NTRS)

    Glass, David E.

    2016-01-01

    Thermal protection systems (TPS) and hot structures are required for a range of hypersonic vehicles ranging from ballistic reentry to hypersonic cruise vehicles, both within Earth's atmosphere and non-Earth atmospheres. The focus of this presentation is on air breathing hypersonic vehicles in the Earth's atmosphere. This includes single-stage to orbit (SSTO), two-stage to orbit (TSTO) accelerators, access to space vehicles, and hypersonic cruise vehicles. This paper will start out with a brief discussion of aerodynamic heating and thermal management techniques to address the high heating, followed by an overview of TPS for rocket-launched and air-breathing vehicles. The argument is presented that as we move from rocket-based vehicles to air-breathing vehicles, we need to move away from the insulated airplane approach used on the Space Shuttle Orbiter to a wide range of TPS and hot structure approaches. The primary portion of the paper will discuss issues and design options for CMC TPS and hot structure components, including leading edges, acreage TPS, and control surfaces. The current state-of-the-art will be briefly discussed for some of the components.

  11. Use of Pom Pons To Illustrate Cubic Crystal Structures

    NASA Astrophysics Data System (ADS)

    Cady, Susan G.

    1997-07-01

    In general chemistry classes, students are introduced to the ways in which atoms are arranged in cubic crystal structures. Transposing the textbook illustrations into three dimensional structures is difficult for some students. This transitions is easier if a three dimensional model is available for examination. Several 3D models are cited. A quick to assemble, inexpensive, colorful, and durable alternative to these models and styrofoam balls is the use of olefin pom pons. Different sized pom pons can be used to demonstrate how the atomic radius will vary when comparing the different types of cubic crystal unit cells. Being made of a coarse material, pom pons can be stacked to illustrate different packing arrangements such as hexagonal close-packed and cubic close-packed structures. Pom pons make great atoms.

  12. Focusing concave lens using photonic crystals with magnetic materials.

    PubMed

    Yang, Shieh-Yueh; Hong, Chin-Yih; Yang, Hong-Chang

    2006-04-01

    The guided modes lying in the upper gap-edge band in the photonic band structure of photonic crystals have negative values of refractive index. This feature generates many interesting optical phenomena, and some spectacular photonic devices such as focusing slabs have been developed. We report the design of a photonic-crystal, planoconcave lens for focusing incident parallel light, and theoretically analyze the chromatic aberrations for TM and TE modes. In addition to dielectric photonic crystals, the chromatic aberration of a magnetic photonic-crystal planoconcave lens was investigated because the magnetic permeability may also contribute to the periodic index contrast in photonic crystals, especially at long wavelengths. A significant difference was found in the chromatic aberration for a TM mode propagating in a dielectric than in a magnetic photonic-crystal planoconcave lens. PMID:16604781

  13. Synthesis, crystal structure, vibrational spectroscopy, optical properties and theoretical studies of a new organic-inorganic hybrid material: [((CH3)2NH2)(+)]6·[(BiBr6)(3-)]2.

    PubMed

    Ben Ahmed, A; Feki, H; Abid, Y

    2014-12-10

    A new organic-inorganic hybrid material, [((CH3)2NH2)(+)]6·[(BiBr6)(3-)]2, has been synthesized and characterized by X-ray diffraction, FT-IR, Raman spectroscopy and UV-Visible absorption. The studied compound crystallizes in the triclinic system, space group P1¯ with the following parameters: a=8.4749(6)(Å), b=17.1392(12)(Å), c=17.1392(12)(Å), α=117.339(0)°, β=99.487(0)°, γ=99.487(0)° and Z=2. The crystal lattice is composed of a two discrete (BiBr6)(3-) anions surrounded by six ((CH3)2NH2)(+) cations. Complex hydrogen bonding interactions between (BiBr6)(3-) and organic cations from a three-dimensional network. Theoretical calculations were performed using density functional theory (DFT) for studying the molecular structure, vibrational spectra and optical properties of the investigated molecule in the ground state. The full geometry optimization of designed system is performed using DFT method at B3LYP/LanL2DZ level of theory using the Gaussian03. The optimized geometrical parameters obtained by DFT calculations are in good agreement with single crystal XRD data. The vibrational spectral data obtained from FT-IR and Raman spectra are assigned based on the results of the theoretical calculations. The energy and oscillator strength calculated by Time-Dependent Density Functional Theory (TD-DFT) results complements with the experimental findings. The simulated spectra satisfactorily coincide with the experimental UV-Visible spectrum. The results show good consistent with the experiment and confirm the contribution of metal orbital to the HOMO-LUMO boundary. PMID:24967541

  14. Manganese oxide minerals: Crystal structures and economic and environmental significance

    PubMed Central

    Post, Jeffrey E.

    1999-01-01

    Manganese oxide minerals have been used for thousands of years—by the ancients for pigments and to clarify glass, and today as ores of Mn metal, catalysts, and battery material. More than 30 Mn oxide minerals occur in a wide variety of geological settings. They are major components of Mn nodules that pave huge areas of the ocean floor and bottoms of many fresh-water lakes. Mn oxide minerals are ubiquitous in soils and sediments and participate in a variety of chemical reactions that affect groundwater and bulk soil composition. Their typical occurrence as fine-grained mixtures makes it difficult to study their atomic structures and crystal chemistries. In recent years, however, investigations using transmission electron microscopy and powder x-ray and neutron diffraction methods have provided important new insights into the structures and properties of these materials. The crystal structures for todorokite and birnessite, two of the more common Mn oxide minerals in terrestrial deposits and ocean nodules, were determined by using powder x-ray diffraction data and the Rietveld refinement method. Because of the large tunnels in todorokite and related structures there is considerable interest in the use of these materials and synthetic analogues as catalysts and cation exchange agents. Birnessite-group minerals have layer structures and readily undergo oxidation reduction and cation-exchange reactions and play a major role in controlling groundwater chemistry. PMID:10097056

  15. Fourier Analysis and Structure Determination--Part III: X-ray Crystal Structure Analysis.

    ERIC Educational Resources Information Center

    Chesick, John P.

    1989-01-01

    Discussed is single crystal X-ray crystal structure analysis. A common link between the NMR imaging and the traditional X-ray crystal structure analysis is reported. Claims that comparisons aid in the understanding of both techniques. (MVL)

  16. Can antimonide-based nanowires form wurtzite crystal structure?

    PubMed

    Gorji Ghalamestani, Sepideh; Lehmann, Sebastian; Dick, Kimberly A

    2016-02-01

    The epitaxial growth of antimonide-based nanowires has become an attractive subject due to their interesting properties required for various applications such as long-wavelength IR detectors. The studies conducted on antimonide-based nanowires indicate that they preferentially crystallize in the zinc blende (ZB) crystal structure rather than wurtzite (WZ), which is common in other III-V nanowire materials. Also, with the addition of small amounts of antimony to arsenide- and phosphide-based nanowires grown under conditions otherwise leading to WZ structure, the crystal structure of the resulting ternary nanowires favors the ZB phase. Therefore, the formation of antimonide-based nanowires with the WZ phase presents fundamental challenges and is yet to be explored, but is particularly interesting for understanding the nanowire crystal phase in general. In this study, we examine the formation of Au-seeded InSb and GaSb nanowires under various growth conditions using metalorganic vapor phase epitaxy. We address the possibility of forming other phases than ZB such as WZ and 4H in binary nanowires and demonstrate the controlled formation of WZ InSb nanowires. We further discuss the fundamental aspects of WZ growth in Au-seeded antimonide-based nanowires. PMID:26763161

  17. Single Crystal Structure Determination of Alumina to 1 Mbar

    NASA Astrophysics Data System (ADS)

    Dong, H.; Zhang, L.; Prakapenka, V.; Mao, H.

    2014-12-01

    Aluminum oxide (Al2O3) is an important ceramic material and a major oxide in the earth. Additionally, alumina is a widely used pressure standard in static high-pressure experiments (Cr3+-bearing corundum, ruby). The changes of its crystal structure with pressure (P) and temperature (T) are important for its applications and understanding its physical properties in the deep Earth. There have been numerous reports on the high P-T polymorphs of alumina. Previous theoretical calculations and experiments suggest that the crystal structure of Al2O3 evolves greatly at high P-T. In this study, we used the newly developed multigrain crystallography method combined with single-crystal x-ray diffraction analysis technique for the structure determination of alumina at high P-T to provide single-crystal structure refinement for high-pressure phases of Al2O3. Alumina powder was mixed with ~10% Pt and Ne was used as both pressure transmitting media and thermal insulating layers during laser-heating. Coarse-grained aggregates of Al2O3 were synthesized in a laser-heated diamond anvil cell. The structure change of Al2O3 was monitored by in situ x-ray diffraction at ~1 Mbar and 2700 K. The results allow us to distinguish the structural differences between the Rh2O3 (II) structure (space group Pbcn) and perovskite structure (space group Pbnm) for the first high-pressure phase of Al2O3. More detailed results will be discussed in the later work.

  18. Structural studies on ferroelectric and ferrodistortive materials

    NASA Astrophysics Data System (ADS)

    Zou, Mingqin

    The structure of the piezoelectric material 0.68PbMg1/3Nb 2/3O3-0.32PbTiO3 have been studied by single crystal, powder x-ray diffraction techniques over the temperature range from 25°C to 200°C. The existence of twinned structures or coexistence of rhombohedral and tetragonal phases has been shown by the peak distortion of Bragg reflections. Superlattice structure was observed for all experimental PMN-PT crystals. Refinement results showed that the 2 x 2 x 2 superlattice resulted from anti-parallel displacement of oxygen in the adjacent conventional perovskite unit cells. No cation displacement in the paraelectric phase and little in the ferroelectric phase were shown by the refinement results. This unique feature associated with the ferroelectric mechanism of the material was explained by comparison with PbMg1/3Nb2/3O3. The crystals were extensively characterized by using powder x-ray diffraction, Laue back-reflection and electron backscatter diffraction (EBSD) techniques. The detailed orientation information such as misorientation of grains, location of grain boundaries and the orientation distribution was obtained from the automatic orientation mapping with the EBSD technique. The uniform orientation was confirmed for crystals with a "cellular-like" structure. A crystal growth model, the two-dimensional layer mechanism, was proposed by orientation analysis. Based on the model, some important comments were made on orientation problems under general growth conditions. The ferrodistortive phase transitions of tertramethylphosphonium tetrabromozincate [P(CH3)4]2ZnBr4 and tertramethylphosphonium tetraiodonzincate [P(CH3)4]2ZnI4 were thoroughly studied by a single crystal x-ray diffraction technique. An order parameter analysis by application of Landau theory showed that the two compounds undergo first-order phase transitions near a tricritical Lifshitz point. Transitions for both compounds appear to be first order, but with the iodo salt the transition is nearly

  19. Crystal Structure of the Protealysin Precursor

    PubMed Central

    Demidyuk, Ilya V.; Gromova, Tania Yu.; Polyakov, Konstantin M.; Melik-Adamyan, William R.; Kuranova, Inna P.; Kostrov, Sergey V.

    2010-01-01

    Protealysin (PLN) belongs to the M4 family of peptidases that are commonly known as thermolysin-like proteases (TLPs). All TLPs are synthesized as precursors containing N-terminal propeptides. According to the primary structure of the N-terminal propeptides, the family is divided into two distinct groups. Representatives of the first group including thermolysin and all TLPs with known three-dimensional structures have long prosequences (∼200 amino acids). Enzymes of the second group, whose prototype is protealysin, have short (∼50 amino acids) propeptides. Here, we present the 1.8 Å crystal structure of PLN precursor (proPLN), which is the first three-dimensional structure of a TLP precursor. Whereas the structure of the catalytic domain of proPLN is similar overall to previously reported structures of mature TLPs, it has specific features, including the absence of calcium-binding sites, and different structures of the N-terminal region and substrate-binding site. PLN propeptide forms a separate domain in the precursor and likely acts as an inhibitor that blocks the substrate-binding site and fixes the “open” conformation of the active site, which is unfavorable for catalysis. Furthermore the conserved PPL motif identified in our previous studies directly interacts with the S′ subsites of the active center being a critical element of the propeptide-catalytic domain interface. Comparison of the primary structures of TLPs with short propeptides suggests that the specific features revealed in the proPLN crystal structure are typical for all protealysin-like enzymes. Thus, such proteins can be considered as a separate subfamily of TLPs. PMID:19915005

  20. Crystal growth of sulfide materials from alkali polysulfide liquids

    NASA Technical Reports Server (NTRS)

    White, W. B.

    1979-01-01

    The fluids experiment system was designed for low temperature solution growth, nominally aqueous solution growth. The alkali polysulfides, compositions in the systems Na2S-S and K2S-S form liquids in the temperature range of 190 C to 400 C. These can be used as solvents for other important classes of materials such as transition metal and other sulfides which are not soluble in aqueous media. Among these materials are luminescent and electroluminescent crystals whose physical properties are sensitive functions of crystal perfection and which could, therefore, serve as test materials for perfection improvement under microgravity conditions.

  1. Analytical ultrasonics for structural materials

    NASA Technical Reports Server (NTRS)

    Kupperman, D. S.

    1986-01-01

    The application of ultrasonic velocity and attenuation measurements to characterize the microstructure of structural materials is discussed. Velocity measurements in cast stainless steel are correlated with microstructural variations ranging from equiaxed (elastically isotropic) to columnar (elastically anisotropic) grain structure. The effect of the anisotropic grain structure on the deviation of ultrasonic waves in cast stainless steel is also reported. Field-implementable techniques for distinguishing equiaxed from columnar grain structures in cast strainless steel structural members are presented. The application of ultrasonic velocity measurements to characterize structural ceramics in the green state is also discussed.

  2. Crystal structure of natural phaeosphaeride A.

    PubMed

    Abzianidze, Victoria V; Poluektova, Ekaterina V; Bolshakova, Ksenia P; Panikorovskii, Taras L; Bogachenkov, Alexander S; Berestetskiy, Alexander O

    2015-08-01

    The asymmetric unit of the title compound, C15H23NO5, contains two independent mol-ecules. Phaeosphaeride A contains two primary sections, an alkyl chain consisting of five C atoms and a cyclic system consisting of fused five- and six-membered rings with attached substituents. In the crystal, the mol-ecules form layered structures. Nearly planar sheets, parallel to the (001) plane, form bilayers of two-dimensional hydrogen-bonded networks with the hy-droxy groups located on the inter-ior of the bilayer sheets. The network is constructed primarily of four O-H⋯O hydrogen bonds, which form a zigzag pattern in the (001) plane. The butyl chains inter-digitate with the butyl chains on adjacent sheets. The crystal was twinned by a twofold rotation about the c axis, with refined major-minor occupancy fractions of 0.718 (6):0.282 (6). PMID:26396831

  3. Crystal structures and freezing of dipolar fluids.

    PubMed

    Groh, B; Dietrich, S

    2001-02-01

    We investigate the crystal structure of classical systems of spherical particles with an embedded point dipole at T=0. The ferroelectric ground state energy is calculated using generalizations of the Ewald summation technique. Due to the reduced symmetry compared to the nonpolar case the crystals are never strictly cubic. For the Stockmayer (i.e., Lennard-Jones plus dipolar) interaction three phases are found upon increasing the dipole moment: hexagonal, body-centered orthorhombic, and body-centered tetragonal. An even richer phase diagram arises for dipolar soft spheres with a purely repulsive inverse power law potential approximately r(-n). A crossover between qualitatively different sequences of phases occurs near the exponent n=12. The results are applicable to electro- and magnetorheological fluids. In addition to the exact ground state analysis we study freezing of the Stockmayer fluid by density-functional theory. PMID:11308482

  4. Layer like porous materials with hierarchical structure.

    PubMed

    Roth, Wieslaw J; Gil, Barbara; Makowski, Wacław; Marszalek, Bartosz; Eliášová, Pavla

    2016-06-13

    Many chemical compositions produce layered solids consisting of extended sheets with thickness not greater than a few nanometers. The layers are weakly bonded together in a crystal and can be modified into various nanoarchitectures including porous hierarchical structures. Several classes of 2-dimensional (2D) materials have been extensively studied and developed because of their potential usefulness as catalysts and sorbents. They are discussed in this review with focus on clays, layered transition metal oxides, silicates, layered double hydroxides, metal(iv) phosphates and phosphonates, especially zirconium, and zeolites. Pillaring and delamination are the primary methods for structural modification and pore tailoring. The reported approaches are described and compared for the different classes of materials. The methods of characterization include identification by X-ray diffraction and microscopy, pore size analysis and activity assessment by IR spectroscopy and catalytic testing. The discovery of layered zeolites was a fundamental breakthrough that created unprecedented opportunities because of (i) inherent strong acid sites that make them very active catalytically, (ii) porosity through the layers and (iii) bridging of 2D and 3D structures. Approximately 16 different types of layered zeolite structures and modifications have been identified as distinct forms. It is also expected that many among the over 200 recognized zeolite frameworks can produce layered precursors. Additional advances enabled by 2D zeolites include synthesis of layered materials by design, hierarchical structures obtained by direct synthesis and top-down preparation of layered materials from 3D frameworks. PMID:26489452

  5. Fire retardancy with structural materials

    NASA Technical Reports Server (NTRS)

    Gardner, R. E.

    1971-01-01

    Impregnating wood with chemicals to reduce or prevent combustion is discussed. Basic types of materials for fireproofing purposes and methods of applications are described. It is concluded that effective fireproofing materials have been developed and their application to wooden structures represents acceptable safety management procedures.

  6. Optimal lattice-structured materials

    DOE PAGESBeta

    Messner, Mark C.

    2016-07-09

    This paper describes a method for optimizing the mesostructure of lattice-structured materials. These materials are periodic arrays of slender members resembling efficient, lightweight macroscale structures like bridges and frame buildings. Current additive manufacturing technologies can assemble lattice structures with length scales ranging from nanometers to millimeters. Previous work demonstrates that lattice materials have excellent stiffness- and strength-to-weight scaling, outperforming natural materials. However, there are currently no methods for producing optimal mesostructures that consider the full space of possible 3D lattice topologies. The inverse homogenization approach for optimizing the periodic structure of lattice materials requires a parameterized, homogenized material model describingmore » the response of an arbitrary structure. This work develops such a model, starting with a method for describing the long-wavelength, macroscale deformation of an arbitrary lattice. The work combines the homogenized model with a parameterized description of the total design space to generate a parameterized model. Finally, the work describes an optimization method capable of producing optimal mesostructures. Several examples demonstrate the optimization method. One of these examples produces an elastically isotropic, maximally stiff structure, here called the isotruss, that arguably outperforms the anisotropic octet truss topology.« less

  7. The First Mammalian Aldehyde Oxidase Crystal Structure

    PubMed Central

    Coelho, Catarina; Mahro, Martin; Trincão, José; Carvalho, Alexandra T. P.; Ramos, Maria João; Terao, Mineko; Garattini, Enrico; Leimkühler, Silke; Romão, Maria João

    2012-01-01

    Aldehyde oxidases (AOXs) are homodimeric proteins belonging to the xanthine oxidase family of molybdenum-containing enzymes. Each 150-kDa monomer contains a FAD redox cofactor, two spectroscopically distinct [2Fe-2S] clusters, and a molybdenum cofactor located within the protein active site. AOXs are characterized by broad range substrate specificity, oxidizing different aldehydes and aromatic N-heterocycles. Despite increasing recognition of its role in the metabolism of drugs and xenobiotics, the physiological function of the protein is still largely unknown. We have crystallized and solved the crystal structure of mouse liver aldehyde oxidase 3 to 2.9 Å. This is the first mammalian AOX whose structure has been solved. The structure provides important insights into the protein active center and further evidence on the catalytic differences characterizing AOX and xanthine oxidoreductase. The mouse liver aldehyde oxidase 3 three-dimensional structure combined with kinetic, mutagenesis data, molecular docking, and molecular dynamics studies make a decisive contribution to understand the molecular basis of its rather broad substrate specificity. PMID:23019336

  8. Crystal structure of MboIIA methyltransferase.

    SciTech Connect

    Osipiuk, J.; Walsh, M. A.; Joachimiak, A.; Biosciences Division; Univ. of Gdansk; Medical Research Council France

    2003-09-15

    DNA methyltransferases (MTases) are sequence-specific enzymes which transfer a methyl group from S-adenosyl-L-methionine (AdoMet) to the amino group of either cytosine or adenine within a recognized DNA sequence. Methylation of a base in a specific DNA sequence protects DNA from nucleolytic cleavage by restriction enzymes recognizing the same DNA sequence. We have determined at 1.74 {angstrom} resolution the crystal structure of a {beta}-class DNA MTase MboIIA (M {center_dot} MboIIA) from the bacterium Moraxella bovis, the smallest DNA MTase determined to date. M {center_dot} MboIIA methylates the 3' adenine of the pentanucleotide sequence 5'-GAAGA-3'. The protein crystallizes with two molecules in the asymmetric unit which we propose to resemble the dimer when M {center_dot} MboIIA is not bound to DNA. The overall structure of the enzyme closely resembles that of M {center_dot} RsrI. However, the cofactor-binding pocket in M {center_dot} MboIIA forms a closed structure which is in contrast to the open-form structures of other known MTases.

  9. The crystal structure of ice under mesospheric conditions

    NASA Astrophysics Data System (ADS)

    Murray, Benjamin J.; Malkin, Tamsin L.; Salzmann, Christoph G.

    2015-05-01

    Ice clouds form in the summer high latitude mesopause region, which is the coldest part of the Earth's atmosphere. At these very low temperatures (<150 K) ice can exist in metastable forms, but the nature of these ices remains poorly understood. In this paper we show that ice which is grown at mesospherically relevant temperatures does not have a structure corresponding to the well-known hexagonal form or the metastable cubic form. Instead, the ice which forms under mesospheric conditions is a material in which cubic and hexagonal sequences of ice are randomly arranged to produce stacking disordered ice (ice Isd). The structure of this ice is in the trigonal crystal system, rather than the cubic or hexagonal systems, and is expected to produce crystals with aspect ratios consistent with lidar observations.

  10. Liquid crystal photoalignment material based on chloromethylated polyimide

    SciTech Connect

    Zhong Zhenxin; Li Xiangdan; Lee, Seung Hee; Lee, Myong-Hoon

    2004-09-27

    We report a liquid crystal photoalignment material with high photosensitivity and excellent thermal stability. The chloromethylated aromatic polyimide exhibited defect-free homogeneous alignment of liquid crystals upon irradiation of polarized deep ultraviolet (UV) for 50 s. The aligning ability of the film was retained up to 210 deg. C, and the cell containing liquid crystals could be stored at 85 deg. C for more than 14 days without any deterioration. FT-IR and UV-vis spectra confirmed that the alignment was induced by photodecomposition of polyimide, drastically accelerated by the introduction of chloromethyl side group.

  11. Constitutive Modeling of Superalloy Single Crystals and Directionally Solidified Materials

    NASA Technical Reports Server (NTRS)

    Walker, K. P.; Jordan, E. H.

    1985-01-01

    A unified viscoplastic constitutive relation based on crystallographic slip theory was developed for the deformation analysis of nickel base face centered cubic superalloy single crystals at elevated temperature. The single crystal theory is embedded in a self consistent method to derive a constitutive relation for a directionally solidified material comprised of a polycrystalline aggregate of columnar cylindrical grains. One of the crystallographic axes of the cylindrical crystals points in the columnar direction while the remaining crystallographic axes are oriented at random in the basal plane perpendicular to the columnar direction. These constitutive formulations are coded in FORTRAN for use in nonlinear finite element and boundary element programs.

  12. Crystal Structure of the 30S Ribosomal Subunit from Thermus Thermophilus. Purification, Crystallization and Structure Determination

    SciTech Connect

    Clemons, William M.; Brodersen, Ditlev E.; McCutcheonn, John P.; May, Joanna L.C.; Carter, Andrew P.; Morgan-Warren, Robert J.; Wimberly, Brian T.; Ramakrishnan, Venki

    2009-10-07

    We describe the crystallization and structure determination of the 30 S ribosomal subunit from Thermus thermophilus. Previous reports of crystals that diffracted to 10 {angstrom} resolution were used as a starting point to improve the quality of the diffraction. Eventually, ideas such as the addition of substrates or factors to eliminate conformational heterogeneity proved less important than attention to detail in yielding crystals that diffracted beyond 3 {angstrom} resolution. Despite improvements in technology and methodology in the last decade, the structure determination of the 30 S subunit presented some very challenging technical problems because of the size of the asymmetric unit, crystal variability and sensitivity to radiation damage. Some steps that were useful for determination of the atomic structure were: the use of anomalous scattering from the LIII edges of osmium and lutetium to obtain the necessary phasing signal; the use of tunable, third-generation synchrotron sources to obtain data of reasonable quality at high resolution; collection of derivative data precisely about a mirror plane to preserve small anomalous differences between Bijvoet mates despite extensive radiation damage and multi-crystal scaling; the pre-screening of crystals to ensure quality, isomorphism and the efficient use of scarce third-generation synchrotron time; pre-incubation of crystals in cobalt hexaammine to ensure isomorphism with other derivatives; and finally, the placement of proteins whose structures had been previously solved in isolation, in conjunction with biochemical data on protein-RNA interactions, to map out the architecture of the 30 S subunit prior to the construction of a detailed atomic-resolution model.

  13. Critical parameters of superconducting materials and structures

    SciTech Connect

    Fluss, M.J.; Howell, R.H.; Sterne, P.A.; Dykes, J.W.; Mosley, W.D.; Chaiken, A.; Ralls, K.; Radousky, H.

    1995-02-01

    We report here the completion of a one year project to investigate the synthesis, electronic structure, defect structure, and physical transport properties of high temperature superconducting oxide materials. During the course of this project we produced some of the finest samples of single crystal detwinned YBa{sub 2}Cu{sub 3}O{sub 7}, and stoichiometrically perfect (Ba,K)BiO{sub 3}. We deduced the Fermi surface of YBa{sub 2}Cu{sub 3}O{sub 7}, (La,Sr){sub 2}CuO{sub 4}, and (Ba,K)BiO{sub 3} through the recording of the electron momentum density in these materials as measured by positron annihilation spectroscopy and angle resolved photoemission. We also performed extensive studies on Pr substituted (Y,Pr)Ba{sub 2}Cu{sub 3}O{sub 7} so as to further understand the origin of the electron pairing leading to superconductivity.

  14. Active photonic crystal devices in self-assembled electro-optic polymeric materials

    NASA Astrophysics Data System (ADS)

    Li, J.; Neyman, P. J.; Vercellino, M.; Heflin, J. R.; Duncan, R.; Evoy, S.

    2004-03-01

    Photonic crystals (PC) offer novel and potent approaches for the control of light compared to traditional technologies. The development of a photonic crystal technology in electro-optic (EO) materials would now provide a novel approach for the development and integration of important "active devices" such as switch, interferometers, etc. We report the development of an active photonic crystal technology that uses ionically self-assembled multilayer (ISAM) as materials platform. Specifically, we concentrate on ISAM film grown from the alternate deposition of individual monolayers of Procion Red MX-5B (PR) and poly(allylamine hydrochloride) (PAH). Films grown with this method show a second harmonic generation (SHG) factor (2) as high as 11 x 10-9 esu, and a r33 coefficient of 3 pm/V. Active photonic crystal are designed and demonstrated in this material using the FEMLAB software. In a first design, a simple switch is implemented by simple shift of the photonic crystal bandgap of a waveguiding structure. A Mach-Zehnder photonic crystal interferometer structure is also demonstrated, in which a 1800 phase shift is obtained between the two arms. We will report on the preliminary realization of active photonic devices using this material self-assembly and nanofabrication platform.

  15. Flowing crystals: nonequilibrium structure of foam.

    PubMed

    Garstecki, Piotr; Whitesides, George M

    2006-07-14

    Bubbles pushed through a quasi-two-dimensional channel self-organize into a variety of periodic lattices. The structures of these lattices correspond to local minima of the interfacial energy. The "flowing crystals" are long-lived metastable states, a small subset of possible local minima of confined quasi-two-dimensional foams [P. Garstecki and G. M. Whitesides, Phys. Rev. E 73, 031603 (2006)10.1103/PhysRevE.73.031603]. Experimental results suggest that the choice of the structures that we observe is dictated by the dynamic stability of the cyclic processes of their formation. Thus, the dynamic system that we report provides a unique example of nonequilibrium self-organization that results in structures that correspond to local minima of the relevant energy functional. PMID:16907453

  16. Crystal structure of plant photosystem I

    NASA Astrophysics Data System (ADS)

    Ben-Shem, Adam; Frolow, Felix; Nelson, Nathan

    2003-12-01

    Oxygenic photosynthesis is the principal producer of both oxygen and organic matter on Earth. The conversion of sunlight into chemical energy is driven by two multisubunit membrane protein complexes named photosystem I and II. We determined the crystal structure of the complete photosystem I (PSI) from a higher plant (Pisum sativum var. alaska) to 4.4Å resolution. Its intricate structure shows 12 core subunits, 4 different light-harvesting membrane proteins (LHCI) assembled in a half-moon shape on one side of the core, 45 transmembrane helices, 167 chlorophylls, 3 Fe-S clusters and 2 phylloquinones. About 20 chlorophylls are positioned in strategic locations in the cleft between LHCI and the core. This structure provides a framework for exploration not only of energy and electron transfer but also of the evolutionary forces that shaped the photosynthetic apparatus of terrestrial plants after the divergence of chloroplasts from marine cyanobacteria one billion years ago.

  17. Crystal Structure Prediction from First Principles: The Crystal Structures of Glycine

    PubMed Central

    Lund, Albert M.; Pagola, Gabriel I.; Orendt, Anita M.; Ferraro, Marta B.; Facelli, Julio C.

    2015-01-01

    Here we present the results of our unbiased searches of glycine polymorphs obtained using the Genetic Algorithms search implemented in Modified Genetic Algorithm for Crystals coupled with the local optimization and energy evaluation provided by Quantum Espresso. We demonstrate that it is possible to predict the crystal structures of a biomedical molecule using solely first principles calculations. We were able to find all the ambient pressure stable glycine polymorphs, which are found in the same energetic ordering as observed experimentally and the agreement between the experimental and predicted structures is of such accuracy that the two are visually almost indistinguishable. PMID:25843964

  18. Crystal structure prediction from first principles: The crystal structures of glycine

    NASA Astrophysics Data System (ADS)

    Lund, Albert M.; Pagola, Gabriel I.; Orendt, Anita M.; Ferraro, Marta B.; Facelli, Julio C.

    2015-04-01

    Here we present the results of our unbiased searches of glycine polymorphs obtained using the genetic algorithms search implemented in MGAC, modified genetic algorithm for crystals, coupled with the local optimization and energy evaluation provided by Quantum Espresso. We demonstrate that it is possible to predict the crystal structures of a biomedical molecule using solely first principles calculations. We were able to find all the ambient pressure stable glycine polymorphs, which are found in the same energetic ordering as observed experimentally and the agreement between the experimental and predicted structures is of such accuracy that the two are visually almost indistinguishable.

  19. Bio-Inspired Approaches to Crystals with Composite Structures

    NASA Astrophysics Data System (ADS)

    Meldrum, Fiona

    2013-03-01

    Advances in technology demand an ever-increasing degree of control over material structure, properties and function. As the properties of monolithic materials are necessary limited, one route to extending them is to create a composite by combining contrasting materials. The potential of this approach is beautifully illustrated by the formation of biominerals where organic macromolecules are combined with brittle minerals such as calcite to create crystals with considerable fracture toughness. This talk will discuss how bio-inspired approaches can be used to generate single crystals with composite crystals through a simple one-pot method. By precipitating calcite crystals in the presence of ``occlusion species'' ranging from latex particles, to organic and inorganic nanoparticles and finally small molecules we demonstrate that high amounts of foreign species can be incorporated through control over the additive surface chemistry, and that this can lead to an enhancement of the mechanical properties of the calcite. Occlusion of 20 nm anionic diblock copolymer micelles was achieved at levels of over 13 wt%, and the properties of the resuktant composite calcite crystals were measured using a range of techniques including IR spectroscopy, high resolution powder XRD and high resolution TEM. Incorporation of these macromolecules leads to crystals with structures and mechanical properties similar to those of biominerals. With sizes in the range of some intracrystalline proteins, the micelles act as ``pseudo-proteins'', thereby providing an excellent model system for investigation of the mechanism of macromolecule insertion within biominerals. Extension of these studies to the incorporation of small molecules (amino acids) again demonstrated high levels of incorporation without any change in the crystal morphology. Further, occlusion of these small molecules within the calcite lattice again resulted in a significant increase in the hardness of the calcite, a result which

  20. Structural investigation of the potassium vanadomolybdate crystal

    SciTech Connect

    Mucha, D.; Olszewski, P.K.; Napruszewska, B.

    1999-08-01

    Potassium vanadomolybdate KVMoO{sub 6} crystallizes in the orthorhombic system (space group Pnma, a = 10.3478(1) {angstrom}, b = 3.6967(1) {angstrom}, c = 13.3769(2) {angstrom}, Z = 4). With an X-ray powder diffraction technique, its structure was solved and refined by direct and Rietveld methods, respectively (R{sub F} = 3.33, R{sub 1} = 4.70, R{sub wp} = 12.44). The crystals are isostructural with PbV{sub 2}O{sub 6}. Octahedra of two types build chains parallel to the b direction; there is disorder in the octahedra described by different occupation numbers of V and Mo atoms: 0.721(4) and 0.279(4), respectively. Potassium atoms occupy the space between the octahedra chains. They play a decisive role, due to the large ionic radius, in generating both KVMoO{sub 6} and pseudobrannerite, K{sub x}V{sub x}Mo{sub 2{minus}x}O{sub 6} (0.76 {le} x {le} 0.82) structures, contrary to other alkali-metal vanadomolybdates of the brannerite structure type. The melting point of KVMoO{sub 6} was detected at 480 C using the DTA method.

  1. Crystal structure of a DNA catalyst.

    PubMed

    Ponce-Salvatierra, Almudena; Wawrzyniak-Turek, Katarzyna; Steuerwald, Ulrich; Höbartner, Claudia; Pena, Vladimir

    2016-01-14

    Catalysis in biology is restricted to RNA (ribozymes) and protein enzymes, but synthetic biomolecular catalysts can also be made of DNA (deoxyribozymes) or synthetic genetic polymers. In vitro selection from synthetic random DNA libraries identified DNA catalysts for various chemical reactions beyond RNA backbone cleavage. DNA-catalysed reactions include RNA and DNA ligation in various topologies, hydrolytic cleavage and photorepair of DNA, as well as reactions of peptides and small molecules. In spite of comprehensive biochemical studies of DNA catalysts for two decades, fundamental mechanistic understanding of their function is lacking in the absence of three-dimensional models at atomic resolution. Early attempts to solve the crystal structure of an RNA-cleaving deoxyribozyme resulted in a catalytically irrelevant nucleic acid fold. Here we report the crystal structure of the RNA-ligating deoxyribozyme 9DB1 (ref. 14) at 2.8 Å resolution. The structure captures the ligation reaction in the post-catalytic state, revealing a compact folding unit stabilized by numerous tertiary interactions, and an unanticipated organization of the catalytic centre. Structure-guided mutagenesis provided insights into the basis for regioselectivity of the ligation reaction and allowed remarkable manipulation of substrate recognition and reaction rate. Moreover, the structure highlights how the specific properties of deoxyribose are reflected in the backbone conformation of the DNA catalyst, in support of its intricate three-dimensional organization. The structural principles underlying the catalytic ability of DNA elucidate differences and similarities in DNA versus RNA catalysts, which is relevant for comprehending the privileged position of folded RNA in the prebiotic world and in current organisms. PMID:26735012

  2. Temperature dependent spin structures in Hexaferrite crystal

    NASA Astrophysics Data System (ADS)

    Chao, Y. C.; Lin, J. G.; Chun, S. H.; Kim, K. H.

    2016-01-01

    In this work, the Hexaferrite Ba0.5Sr1.5Zn2Fe12O22 (BSZFO) is studied due to its interesting characteristics of long-wavelength spin structure. Ferromagnetic resonance (FMR) is used to probe the magnetic states of BSZFO single crystal and its temperature dependence behavior is analyzed by decomposing the multiple lines of FMR spectra into various phases. Distinguished phase transition is observed at 110 K for one line, which is assigned to the ferro(ferri)-magnetic transition from non-collinear to collinear spin state.

  3. Growth of bulk single crystals of organic materials for nonlinear optical devices - An overview

    NASA Technical Reports Server (NTRS)

    Penn, Benjamin G.; Cardelino, Beatriz H.; Moore, Craig E.; Shields, Angela W.; Frazier, D. O.

    1991-01-01

    Highly perfect single crystals of nonlinear optical organic materials are required for use in optical devices. An overview of the bulk crystal growth of these materials by melt, vapor, and solution processes is presented. Additionally, methods that may be used to purify starting materials, detect impurities at low levels, screen materials for crystal growth, and process grown crystals are discussed.

  4. Revisiting the crystal structure of rhombohedral lead metaniobate.

    PubMed

    Olsen, Gerhard Henning; Sørby, Magnus Helgerud; Hauback, Bjørn Christian; Selbach, Sverre Magnus; Grande, Tor

    2014-09-15

    Lead metaniobate (PbNb2O6) can exist both as a stable rhombohedral and a metastable orthorhombic tungsten-bronze-type polymorph. Although the orthorhombic is a well-known ferroelectric material, the rhombohedral polymorph has been far less studied. The crystal structure and energetic stability of the stable rhombohedral polymorph of lead metaniobate is re-examined by powder X-ray diffraction and powder neutron diffraction in combination with ab initio calculations. We show that this structure is described by the polar space group R3, in contradiction to the previously reported space group R3m. The crystal structure is unusual, consisting of edge-sharing dimers of NbO(6/2) octahedra forming layers with 6- and 3-fold rings of octahedra and lead ions in channels formed by these rings. The layers are connected by corner-sharing between octahedra. Finally, the crystal structure is discussed in relation to other AB2O6 compounds with B = Nb, Ta. PMID:25167129

  5. Monoolein lipid phases as incorporation and enrichment materials for membrane protein crystallization.

    SciTech Connect

    Wallace, E.; Dranow, D.; Laible, P. D.; Christensen, J.; Nollert, P.

    2011-01-01

    The crystallization of membrane proteins in amphiphile-rich materials such as lipidic cubic phases is an established methodology in many structural biology laboratories. The standard procedure employed with this methodology requires the generation of a highly viscous lipidic material by mixing lipid, for instance monoolein, with a solution of the detergent solubilized membrane protein. This preparation is often carried out with specialized mixing tools that allow handling of the highly viscous materials while minimizing dead volume to save precious membrane protein sample. The processes that occur during the initial mixing of the lipid with the membrane protein are not well understood. Here we show that the formation of the lipidic phases and the incorporation of the membrane protein into such materials can be separated experimentally. Specifically, we have investigated the effect of different initial monoolein-based lipid phase states on the crystallization behavior of the colored photosynthetic reaction center from Rhodobacter sphaeroides. We find that the detergent solubilized photosynthetic reaction center spontaneously inserts into and concentrates in the lipid matrix without any mixing, and that the initial lipid material phase state is irrelevant for productive crystallization. A substantial in-situ enrichment of the membrane protein to concentration levels that are otherwise unobtainable occurs in a thin layer on the surface of the lipidic material. These results have important practical applications and hence we suggest a simplified protocol for membrane protein crystallization within amphiphile rich materials, eliminating any specialized mixing tools to prepare crystallization experiments within lipidic cubic phases. Furthermore, by virtue of sampling a membrane protein concentration gradient within a single crystallization experiment, this crystallization technique is more robust and increases the efficiency of identifying productive crystallization

  6. Glass Formation of a Coordination Polymer Crystal for Enhanced Proton Conductivity and Material Flexibility.

    PubMed

    Chen, Wenqian; Horike, Satoshi; Umeyama, Daiki; Ogiwara, Naoki; Itakura, Tomoya; Tassel, Cédric; Goto, Yoshihiro; Kageyama, Hiroshi; Kitagawa, Susumu

    2016-04-18

    The glassy state of a two-dimensional (2D) Cd(2+) coordination polymer crystal was prepared by a solvent-free mechanical milling process. The glassy state retains the 2D structure of the crystalline material, albeit with significant distortion, as characterized by synchrotron X-ray analyses and solid-state multinuclear NMR spectroscopy. It transforms to its original crystal structure upon heating. Thus, reversible crystal-to-glass transformation is possible using our new processes. The glass state displays superior properties compared to the crystalline state; specifically, it shows anhydrous proton conductivity and a dielectric constant two orders of magnitude greater than the crystalline material. It also shows material flexibility and transparency. PMID:26990042

  7. Nanoscale Imaging of Mineral Crystals inside Biological Composite Materials Using X-Ray Diffraction Microscopy

    NASA Astrophysics Data System (ADS)

    Jiang, Huaidong; Ramunno-Johnson, Damien; Song, Changyong; Amirbekian, Bagrat; Kohmura, Yoshiki; Nishino, Yoshinori; Takahashi, Yukio; Ishikawa, Tetsuya; Miao, Jianwei

    2008-01-01

    We for the first time applied x-ray diffraction microscopy to the imaging of mineral crystals inside biological composite materials—intramuscular fish bone—at the nanometer scale resolution. We identified mineral crystals in collagen fibrils at different stages of mineralization. Based on the experimental results and biomineralization analyses, we suggested a dynamic model to account for the nucleation and growth of mineral crystals in the collagen matrix. The results obtained from this study not only further our understanding of the complex structure of bone, but also demonstrate that x-ray diffraction microscopy will become an important tool to study biological materials.

  8. Crystal structure of yeast Sco1

    SciTech Connect

    Abajian, Carnie; Rosenzweig, Amy C.

    2010-03-05

    The Sco family of proteins are involved in the assembly of the dinuclear CuA site in cytochrome c oxidase (COX), the terminal enzyme in aerobic respiration. These proteins, which are found in both eukaryotes and prokaryotes, are characterized by a conserved CXXXC sequence motif that binds copper ions and that has also been proposed to perform a thiol:disulfide oxidoreductase function. The crystal structures of Saccharomyces cerevisiae apo Sco1 (apo-ySco1) and Sco1 in the presence of copper ions (Cu-ySco1) were determined to 1.8- and 2.3-{angstrom} resolutions, respectively. Yeast Sco1 exhibits a thioredoxin-like fold, similar to that observed for human Sco1 and a homolog from Bacillus subtilis. The Cu-ySco1 structure, obtained by soaking apo-ySco1 crystals in copper ions, reveals an unexpected copper-binding site involving Cys181 and Cys216, cysteine residues present in ySco1 but not in other homologs. The conserved CXXXC cysteines, Cys148 and Cys152, can undergo redox chemistry in the crystal. An essential histidine residue, His239, is located on a highly flexible loop, denoted the Sco loop, and can adopt positions proximal to both pairs of cysteines. Interactions between ySco1 and its partner proteins yeast Cox17 and yeast COX2 are likely to occur via complementary electrostatic surfaces. This high-resolution model of a eukaryotic Sco protein provides new insight into Sco copper binding and function.

  9. The Crystal Structure of Human Argonaute2

    SciTech Connect

    Schirle, Nicole T.; MacRae, Ian J.

    2012-07-18

    Argonaute proteins form the functional core of the RNA-induced silencing complexes that mediate RNA silencing in eukaryotes. The 2.3 angstrom resolution crystal structure of human Argonaute2 (Ago2) reveals a bilobed molecule with a central cleft for binding guide and target RNAs. Nucleotides 2 to 6 of a heterogeneous mixture of guide RNAs are positioned in an A-form conformation for base pairing with target messenger RNAs. Between nucleotides 6 and 7, there is a kink that may function in microRNA target recognition or release of sliced RNA products. Tandem tryptophan-binding pockets in the PIWI domain define a likely interaction surface for recruitment of glycine-tryptophan-182 (GW182) or other tryptophan-rich cofactors. These results will enable structure-based approaches for harnessing the untapped therapeutic potential of RNA silencing in humans.

  10. Crystal structure of human nicotinamide riboside kinase.

    PubMed

    Khan, Javed A; Xiang, Song; Tong, Liang

    2007-08-01

    Nicotinamide riboside kinase (NRK) has an important role in the biosynthesis of NAD(+) as well as the activation of tiazofurin and other NR analogs for anticancer therapy. NRK belongs to the deoxynucleoside kinase and nucleoside monophosphate (NMP) kinase superfamily, although the degree of sequence conservation is very low. We report here the crystal structures of human NRK1 in a binary complex with the reaction product nicotinamide mononucleotide (NMN) at 1.5 A resolution and in a ternary complex with ADP and tiazofurin at 2.7 A resolution. The active site is located in a groove between the central parallel beta sheet core and the LID and NMP-binding domains. The hydroxyl groups on the ribose of NR are recognized by Asp56 and Arg129, and Asp36 is the general base of the enzyme. Mutation of residues in the active site can abolish the catalytic activity of the enzyme, confirming the structural observations. PMID:17698003

  11. Crystal Structure of Human Nicotinamide Riboside Kinase

    SciTech Connect

    Khan,J.; Xiang, S.; Tong, L.

    2007-01-01

    Nicotinamide riboside kinase (NRK) has an important role in the biosynthesis of NAD{sup +} as well as the activation of tiazofurin and other NR analogs for anticancer therapy. NRK belongs to the deoxynucleoside kinase and nucleoside monophosphate (NMP) kinase superfamily, although the degree of sequence conservation is very low. We report here the crystal structures of human NRK1 in a binary complex with the reaction product nicotinamide mononucleotide (NMN) at 1.5 {angstrom} resolution and in a ternary complex with ADP and tiazofurin at 2.7 {angstrom} resolution. The active site is located in a groove between the central parallel {beta} sheet core and the LID and NMP-binding domains. The hydroxyl groups on the ribose of NR are recognized by Asp56 and Arg129, and Asp36 is the general base of the enzyme. Mutation of residues in the active site can abolish the catalytic activity of the enzyme, confirming the structural observations.

  12. The crystal structure of human Argonaute2.

    PubMed

    Schirle, Nicole T; MacRae, Ian J

    2012-05-25

    Argonaute proteins form the functional core of the RNA-induced silencing complexes that mediate RNA silencing in eukaryotes. The 2.3 angstrom resolution crystal structure of human Argonaute2 (Ago2) reveals a bilobed molecule with a central cleft for binding guide and target RNAs. Nucleotides 2 to 6 of a heterogeneous mixture of guide RNAs are positioned in an A-form conformation for base pairing with target messenger RNAs. Between nucleotides 6 and 7, there is a kink that may function in microRNA target recognition or release of sliced RNA products. Tandem tryptophan-binding pockets in the PIWI domain define a likely interaction surface for recruitment of glycine-tryptophan-182 (GW182) or other tryptophan-rich cofactors. These results will enable structure-based approaches for harnessing the untapped therapeutic potential of RNA silencing in humans. PMID:22539551

  13. Crystal structure of mammalian acid sphingomyelinase.

    PubMed

    Gorelik, Alexei; Illes, Katalin; Heinz, Leonhard X; Superti-Furga, Giulio; Nagar, Bhushan

    2016-01-01

    Acid sphingomyelinase (ASMase, ASM, SMPD1) converts sphingomyelin into ceramide, modulating membrane properties and signal transduction. Inactivating mutations in ASMase cause Niemann-Pick disease, and its inhibition is also beneficial in models of depression and cancer. To gain a better understanding of this critical therapeutic target, we determined crystal structures of mammalian ASMase in various conformations. The catalytic domain adopts a calcineurin-like fold with two zinc ions and a hydrophobic track leading to the active site. Strikingly, the membrane interacting saposin domain assumes either a closed globular conformation independent from the catalytic domain, or an open conformation, which establishes an interface with the catalytic domain essential for activity. Structural mapping of Niemann-Pick mutations reveals that most of them likely destabilize the protein's fold. This study sheds light on the molecular mechanism of ASMase function, and provides a platform for the rational development of ASMase inhibitors and therapeutic use of recombinant ASMase. PMID:27435900

  14. Crystal structure of mammalian acid sphingomyelinase

    PubMed Central

    Gorelik, Alexei; Illes, Katalin; Heinz, Leonhard X.; Superti-Furga, Giulio; Nagar, Bhushan

    2016-01-01

    Acid sphingomyelinase (ASMase, ASM, SMPD1) converts sphingomyelin into ceramide, modulating membrane properties and signal transduction. Inactivating mutations in ASMase cause Niemann–Pick disease, and its inhibition is also beneficial in models of depression and cancer. To gain a better understanding of this critical therapeutic target, we determined crystal structures of mammalian ASMase in various conformations. The catalytic domain adopts a calcineurin-like fold with two zinc ions and a hydrophobic track leading to the active site. Strikingly, the membrane interacting saposin domain assumes either a closed globular conformation independent from the catalytic domain, or an open conformation, which establishes an interface with the catalytic domain essential for activity. Structural mapping of Niemann–Pick mutations reveals that most of them likely destabilize the protein's fold. This study sheds light on the molecular mechanism of ASMase function, and provides a platform for the rational development of ASMase inhibitors and therapeutic use of recombinant ASMase. PMID:27435900

  15. Structure, thermodynamics, and crystallization of amorphous hafnia

    NASA Astrophysics Data System (ADS)

    Luo, Xuhui; Demkov, Alexander A.

    2015-09-01

    We investigate theoretically amorphous hafnia using the first principles melt and quench method. We identify two types of amorphous structures of hafnia. Type I and type II are related to tetragonal and monoclinic hafnia, respectively. We find type II structure to show stronger disorder than type I. Using the phonon density of states, we calculate the specific heat capacity for type II amorphous hafnia. Using the nudged elastic band method, we show that the averaged transition barrier between the type II amorphous hafnia and monoclinic phase is approximately 0.09 eV/HfO2. The crystallization temperature is estimated to be 421 K. The calculations suggest an explanation for the low thermal stability of amorphous hafnia.

  16. Structure, thermodynamics, and crystallization of amorphous hafnia

    SciTech Connect

    Luo, Xuhui; Demkov, Alexander A.

    2015-09-28

    We investigate theoretically amorphous hafnia using the first principles melt and quench method. We identify two types of amorphous structures of hafnia. Type I and type II are related to tetragonal and monoclinic hafnia, respectively. We find type II structure to show stronger disorder than type I. Using the phonon density of states, we calculate the specific heat capacity for type II amorphous hafnia. Using the nudged elastic band method, we show that the averaged transition barrier between the type II amorphous hafnia and monoclinic phase is approximately 0.09 eV/HfO{sub 2}. The crystallization temperature is estimated to be 421 K. The calculations suggest an explanation for the low thermal stability of amorphous hafnia.

  17. Crystal structure and stability of Tl2CO3 at high pressures.

    PubMed

    Grzechnik, A; Friese, K

    2010-03-01

    The crystal structure of dithallium carbonate, Tl(2)CO(3) (C2/m, Z = 4), was investigated at pressures of up to 7.4 GPa using single-crystal X-ray diffraction in a diamond anvil cell. It is stable to at least 5.82 GPa. All atoms except for one of the O atoms lie on crystallographic mirror planes. At higher pressures, the material undergoes a phase transition that destroys the single crystal. PMID:20203393

  18. Crystallization of Stretched Polyimides: A Structure-Property Study

    NASA Technical Reports Server (NTRS)

    Hinkley, Jeffrey A.; Dezern, James F.

    2002-01-01

    A simple rotational isomeric state model was used to detect the degree to which polyimide repeat units might align to give an extended crystal. It was found experimentally that the hallmarks of stretch-crystallization were more likely to occur in materials whose molecules could readily give extended, aligned conformations. A proposed screening criterion was 84% accurate in selecting crystallizing molecules.

  19. Structural studies of tubular discotic liquid crystals

    NASA Astrophysics Data System (ADS)

    Mindyuk, Oksana Yaroslavovna

    1999-11-01

    Discotic liquid crystals based on the rigid ring-shaped phenylacetylene macrocycle molecule (PAM) are of great interest due to their potential organization into supramolecular channels. We have used high resolution X-ray diffraction to study the structure of pure and doped PAM and to demonstrate that PAM forms a tubular columnar liquid crystal with an unexpected distortion and doubling of the underlying hexagonal lattice. We have doped PAM with different percentages of silver ions and determined that doping did not change peak positions on the powder diffraction data but significantly altered the intensity of the peaks. This implies that the silver ions were most likely intercalated within the channels formed by the PAM molecules, thus leaving the lattice parameters unaffected. We have also used grazing incidence X-ray diffraction and X-ray reflectivity to study Langmuir films of PAM. PAM adopts an "edge-on" molecular arrangement at the air-water interface. We will discuss the direct observation of the structural reorganization within macromolecular Langmuir films of disc-shaped ionophoric molecules arising from interactions with potassium and cesium ions in the subphase. The columnar order is disrupted by CsCl in the subphase and strongly enhanced by KCl in the subphase, thus effectively tailoring the structural properties of the Langmuir films for potential applications. We have also used X-ray reflectivity (XR) and grazing incidence x-ray diffraction (GID) to study Langmuir films of another macrocyclic ionophore: torand (tributyldodecahydrohexaazakekulene, "TBDK") molecules. TBDK is a rigid, triangular molecule; it has been investigated as a potential surface-active complexing agent. The system forms a stable monolayer at the air-water interface and exhibits two distinct structural phases at lower and higher pressures.

  20. Structural contribution to the roughness of supersmooth crystal surface

    SciTech Connect

    Butashin, A. V.; Muslimov, A. E. Kanevsky, V. M.; Deryabin, A. N.; Pavlov, V. A.; Asadchikov, V. E.

    2013-05-15

    Technological advances in processing crystals (Si, sapphire {alpha}-Al{sub 2}O{sub 3}, SiC, GaN, LiNbO{sub 3}, SrTiO{sub 3}, etc.) of substrate materials and X-ray optics elements make it possible to obtain supersmooth surfaces with a periodicity characteristic of the crystal structure. These periodic structures are formed by atomically smooth terraces and steps of nano- and subnanometer sizes, respectively. A model surface with such nanostructures is proposed, and the relations between its roughness parameters and the height of atomic steps are determined. The roughness parameters calculated from these relations almost coincide with the experimental atomic force microscopy (AFM) data obtained from 1 Multiplication-Sign 1 and 10 Multiplication-Sign 10 {mu}m areas on the surface of sapphire plates with steps. The minimum roughness parameters for vicinal crystal surfaces, which are due to the structural contribution, are calculated based on the approach proposed. A comparative analysis of the relief and roughness parameters of sapphire plate surfaces with different degrees of polishing is performed. A size effect is established: the relief height distribution changes from stochastic to regular with a decrease in the surface roughness.

  1. Prediction of binary hard-sphere crystal structures.

    PubMed

    Filion, Laura; Dijkstra, Marjolein

    2009-04-01

    We present a method based on a combination of a genetic algorithm and Monte Carlo simulations to predict close-packed crystal structures in hard-core systems. We employ this method to predict the binary crystal structures in a mixture of large and small hard spheres with various stoichiometries and diameter ratios between 0.4 and 0.84. In addition to known binary hard-sphere crystal structures similar to NaCl and AlB2, we predict additional crystal structures with the symmetry of CrB, gammaCuTi, alphaIrV, HgBr2, AuTe2, Ag2Se, and various structures for which an atomic analog was not found. In order to determine the crystal structures at infinite pressures, we calculate the maximum packing density as a function of size ratio for the crystal structures predicted by our GA using a simulated annealing approach. PMID:19518387

  2. Crystal structure of bacterioferritin from Rhodobacter sphaeroides

    SciTech Connect

    Nam, Ki Hyun; Xu, Yongbin; Piao, Shunfu; Priyadarshi, Amit; Lee, Eun Hye; Kim, Hye-Yeon; Jeon, Young Ho; Ha, Nam-Chul; Hwang, Kwang Yeon

    2010-01-01

    Iron is essential for the survival of organisms, but either excess or deficient levels of iron induce oxidative stress, thereby causing cell damage. As a result, iron regulation is essential for proper cell growth and proliferation in most organisms. Bacterioferritin is a ferritin-like family protein that contains a heme molecule and a ferroxidase site at the di-iron center. This protein plays a primary role in intracellular iron storage for iron homeostasis, as well as in the maintenance of iron in a soluble and non-toxic form. Although several bacterioferritin structures have been determined, no structural studies have successfully elucidated the molecular function of the heme molecule and the ferroxidase center. Here, we report the crystal structure of bacterioferritin from Rhodobacter sphaeroides. This protein exists in a roughly spherical configuration via the assembly of 24 subunits. We describe the oligomeric arrangement, ferroxidase center and heme-binding site based on this structure. The protein contains a single iron-binding configuration in the ferroxidase center, which allows for the release of iron by His130 when the protein is in the intermediate state. The heme molecule in RsBfr is stabilized by shifting of the van der Waals interaction center between the porphyrin of the heme and Trp26. We anticipate that further structural analysis will provide a more complete understanding of the molecular mechanisms of members of the ferritin-like family.

  3. Magnetic and Crystal Structure of α-RuCl3

    NASA Astrophysics Data System (ADS)

    Sears, Jennifer

    The layered honeycomb material α-RuCl3 has been proposed as a candidate material to show significant bond-dependent Kitaev type interactions. This has prompted several recent studies of magnetism in this material that have found evidence for multiple magnetic transitions in the temperature range of 8-14 K. We will present elastic neutron scattering measurements collected using a co-aligned array of α-RuCl3 crystals, identifying zigzag magnetic order within the honeycomb planes with an ordering temperature of ~8 K. It has been reported that the ordering temperature depends on the c axis periodicity of the layered structure, with ordering temperatures of 8 and 14 K for three and two-layer periodicity respectively. While the in-plane magnetic order has been identified, it is clear that a complete understanding of magnetic ordering and interactions will depend on the three dimensional structure of the crystal. Evidence of a structural transition at ~150 K has been reported and questions remain about the structural details, in particular the stacking of the honeycomb layers. We will present x-ray diffraction measurements investigating the low and high temperature structures and stacking disorder in α-RuCl3. Finally, we will present inelastic neutron scattering measurements of magnetic excitations in this material. Work done in collaboration with K. W. Plumb (Johns Hopkins University), J. P. Clancy, Young-June Kim (University of Toronto), J. Britten (McMaster University), Yu-Sheng Chen (Argonne National Laboratory), Y. Qiu, Y. Zhao, D. Parshall, and J. W. Lynn (NCNR).

  4. Synthesis, growth, crystal structure and characterization of a new organic NLO crystal: L-Lysine 4-nitrophenolate monohydrate (LLPNP)

    NASA Astrophysics Data System (ADS)

    Mahadevan, M.; Magesh, M.; Ramachandran, K.; Anandan, P.; Arivanandhan, M.; Hayakawa, Y.

    2014-09-01

    L-Lysine 4-nitrophenolate monohydrate (LLPNP) has been synthesized and grown by solution growth method at room temperature using deionised water as a solvent. The crystal structure of the materials was solved by single crystal X-ray diffraction analysis and it was found that the material has orthorhombic system. The crystallinity of the grown crystals was studied by the powder X-ray diffraction analysis. Molecular structure of the grown crystal was investigated by 1H NMR spectroscopy. The various functional groups of the sample were identified by Fourier transform infrared and Fourier transform-Raman spectroscopic analyses. Thermal stability of the grown crystal has been studied by Thermogravimetric and Differential thermal (TG&DTA) analysis. The optical absorption of the grown crystals has been ascertained by UV-Vis-NIR absorption studies. Second harmonic generation (SHG) efficiency of the material has been determined by Kurtz and Perry technique and the efficiency was found to be 4.45 and 1.4 times greater than that of standard KDP and urea samples, respectively.

  5. The crystal and molecular structure of triethanol-ammonium nitrate

    NASA Astrophysics Data System (ADS)

    Bracuti, A. J.

    1992-12-01

    The liquid propellant used in the 155-mm regenerative liquid propellant gun is XM46. XM46 is a solution of 60 percent hydroxyl ammonium nitrate (HAN), 20 percent triethanolammonium nitrate (TEAN), and 20 percent water. This material exhibits rather unusual liquid properties that have been attributed to its being a 'molten eutectic' of fused salts rather than a normal aqueous solution of two different nitrate salts. A hydrogen-bonded liquid structure for eutectic LP1946 was proposed previously based on the known structures of neat HAN and water and a best-guess estimate of the TEAN structure. To verify this estimate, the molecular structure of neat TEAN was recently determined. This investigation revealed TEAN has very unusual and interesting bifurcated intermolecular and trifurcated intramolecular hydrogen bonding configurations within the crystal. If these hydrogen bonding configurations are retained in aqueous solution, they could be responsible in some part to the observed unusual liquid properties of liquid propellant XM46.

  6. Photoresponsive Cyanostilbene Bent-Core Liquid Crystals as New Materials with Light-Driven Modulated Polarization.

    PubMed

    Martínez-Abadía, Marta; Robles-Hernández, Beatriz; de la Fuente, María Rosario; Giménez, Raquel; Ros, Maria Blanca

    2016-08-01

    Two isomeric cyanostilbene photoswitchable bent-core mesogens with polar liquid crystal phases in which macroscopic polarization and luminescence can be light-modulated are introduced. Z/E isomerization or [2+2] cycloaddition photochemical processes occur depending on the chemical structure, which make the compounds very innovative multifunctional advanced materials. PMID:27213889

  7. Crystal structure of strontium dinickel iron orthophosphate

    PubMed Central

    Ouaatta, Said; Assani, Abderrazzak; Saadi, Mohamed; El Ammari, Lahcen

    2015-01-01

    The title compound, SrNi2Fe(PO4)3, synthesized by solid-state reaction, crystallizes in an ordered variant of the α-CrPO4 structure. In the asymmetric unit, two O atoms are in general positions, whereas all others atoms are in special positions of the space group Imma: the Sr cation and one P atom occupy the Wyckoff position 4e (mm2), Fe is on 4b (2/m), Ni and the other P atom are on 8g (2), one O atom is on 8h (m) and the other on 8i (m). The three-dimensional framework of the crystal structure is built up by [PO4] tetra­hedra, [FeO6] octa­hedra and [Ni2O10] dimers of edge-sharing octa­hedra, linked through common corners or edges. This structure comprises two types of layers stacked alternately along the [100] direction. The first layer is formed by edge-sharing octa­hedra ([Ni2O10] dimer) linked to [PO4] tetra­hedra via common edges while the second layer is built up from a strontium row followed by infinite chains of alternating [PO4] tetra­hedra and FeO6 octa­hedra sharing apices. The layers are held together through vertices of [PO4] tetra­hedra and [FeO6] octa­hedra, leading to the appearance of two types of tunnels parallel to the a- and b-axis directions in which the Sr cations are located. Each Sr cation is surrounded by eight O atoms. PMID:26594419

  8. Crystal structures of five 6-mercaptopurine derivatives.

    PubMed

    Gomes, Lígia R; Low, John Nicolson; Magalhães E Silva, Diogo; Cagide, Fernando; Borges, Fernanda

    2016-03-01

    The crystal structures of five 6-mercaptopurine derivatives, viz. 2-[(9-acetyl-9H-purin-6-yl)sulfan-yl]-1-(3-meth-oxy-phen-yl)ethan-1-one (1), C16H14N4O3S, 2-[(9-acetyl-9H-purin-6-yl)sulfan-yl]-1-(4-meth-oxy-phen-yl)ethan-1-one (2), C16H14N4O3S, 2-[(9-acetyl-9H-purin-6-yl)sulfan-yl]-1-(4-chloro-phen-yl)ethan-1-one (3), C15H11ClN4O2S, 2-[(9-acetyl-9H-purin-6-yl)sulfan-yl]-1-(4-bromo-phen-yl)ethan-1-one (4), C15H11BrN4O2S, and 1-(3-meth-oxy-phen-yl)-2-[(9H-purin-6-yl)sulfan-yl]ethan-1-one (5), C14H12N4O2S. Compounds (2), (3) and (4) are isomorphous and accordingly their mol-ecular and supra-molecular structures are similar. An analysis of the dihedral angles between the purine and exocyclic phenyl rings show that the mol-ecules of (1) and (5) are essentially planar but that in the case of the three isomorphous compounds (2), (3) and (4), these rings are twisted by a dihedral angle of approximately 38°. With the exception of (1) all mol-ecules are linked by weak C-H⋯O hydrogen bonds in their crystals. There is π-π stacking in all compounds. A Cambridge Structural Database search revealed the existence of 11 deposited compounds containing the 1-phenyl-2-sulfanyl-ethanone scaffold; of these, only eight have a cyclic ring as substituent, the majority of these being heterocycles. PMID:27006794

  9. Acoustic wave velocities in two-dimensional composite structures based on acousto-optical crystals

    NASA Astrophysics Data System (ADS)

    Mal'neva, P. V.; Trushin, A. S.

    2015-04-01

    Sound velocities in two-dimensional composite structures based on isotropic and anisotropic acousto-optical crystals have been determined by numerical simulations. The isotropic materials are represented by fused quartz (SiO2) and flint glass, while anisotropic materials include tetragonal crystals of paratellurite (TeO2) and rutile (TiO2) and a trigonal crystal of tellurium (Te). It is established that the acoustic anisotropy of periodic composite structures strongly depends on both the chemical composition and geometric parameters of components.

  10. Structural disorder in molecular framework materials.

    PubMed

    Cairns, Andrew B; Goodwin, Andrew L

    2013-06-21

    It is increasingly apparent that many important classes of molecular framework material exhibit a variety of interesting and useful types of structural disorder. This tutorial review summarises a number of recent efforts to understand better both the complex microscopic nature of this disorder and also how it might be implicated in useful functionalities of these materials. We draw on a number of topical examples including topologically-disordered zeolitic imidazolate frameworks (ZIFs), porous aromatic frameworks (PAFs), the phenomena of temperature-, pressure- and desorption-induced amorphisation, partial interpenetration, ferroelectric transition-metal formates, negative thermal expansion in cyanide frameworks, and the mechanics and processing of layered frameworks. We outline the various uses of pair distribution function (PDF) analysis, dielectric spectroscopy, peak-shape analysis of powder diffraction data and single-crystal diffuse scattering measurements as means of characterising disorder in these systems, and we suggest a number of opportunities for future research in the field. PMID:23471316