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1

Solar cell structure incorporating a novel single crystal silicon material  

DOEpatents

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.

Pankove, Jacques I. (Princeton, NJ); Wu, Chung P. (Trenton, NJ)

1983-01-01

2

Materials for Alternative Energies: Computational Materials Discovery and Crystal Structure Prediction  

NASA Astrophysics Data System (ADS)

Many of the key technological problems associated with alternative energies may be traced back to the lack of suitable materials. The materials discovery process may be greatly aided by the use of computational methods, particular those atomistic methods based on density functional theory. In this talk, we present an overview of recent work on energy-related materials from density-functional based approaches. We have developed novel computational tools which enable accurate prediction of crystal structures for new materials (using both Monte Carlo and Genetic Algorithm based approaches), materials discovery via high-throughput, data mining techniques, and automated phase diagram calculations. We highlight applications in the area of Li battery materials and hydrogen storage materials.

Wolverton, Chris

2013-03-01

3

Exploring Materials: Liquid Crystals  

NSDL National Science Digital Library

In this activity, learners discover that the way a material behaves on the macroscale is affected by its structure on the nanoscale. Learners investigate the properties of a heat sensitive liquid crystal and make their own liquid crystal sensor to take home. This is a fun and engaging activity, especially since liquid crystals are used in many consumer products, including cell phone displays, laptop computer screens, strip thermometers, and even "mood" rings! SAFETY: learners must be supervised when doing this activity. They must wear safety glasses to protect their eyes. Before doing this activity, read through the Material Safety Data Sheets.

Network, Nanoscale I.; Sciencenter

2010-01-01

4

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

NASA Technical Reports Server (NTRS)

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.

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

1998-01-01

5

Abinitio determination of crystal structures of the thermoelectric material MgAgSb  

NASA Astrophysics Data System (ADS)

Materials with the half-Heusler structure possess interesting electrical and magnetic properties, including potential for thermoelectric applications. MgAgSb is compositionally and structurally related to many half-Heusler materials but has not been extensively studied. This work presents the high-temperature x-ray diffraction analysis of MgAgSb between 27 and 420 ?C, complemented with thermoelectric property measurements. MgAgSb is found to exist in three different crystal structures in this temperature region, taking the half-Heusler structure at high temperatures, a Cu2Sb-related structure at intermediate temperatures, and a previously unreported tetragonal structure at room temperature. All three structures are related by a distorted Mg-Sb rocksalt-type sublattice, differing primarily in the Ag location among the available tetrahedral sites. Transition temperatures between the three phases correlate well with discontinuities in the Seebeck coefficient and electrical conductivity; the best performance occurs with the novel room temperature phase. For application of MgAgSb as a thermoelectric material, it may be desirable to develop methods to stabilize the room temperature phase at higher temperatures.

Kirkham, Melanie J.; dos Santos, Antonio M.; Rawn, Claudia J.; Lara-Curzio, Edgar; Sharp, Jeff W.; Thompson, Alan J.

2012-04-01

6

Crystal growth, structure and characterizations of a new semiorganic nonlinear optical material?-Alanine zinc chloride  

Microsoft Academic Search

The title compound, ?-alanine zinc chloridea new semiorganic nonlinear optical crystal was grown by slow evaporation technique. Single crystals of ?-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

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

2010-01-01

7

Colloidal crystals as templates for porous materials  

Microsoft Academic Search

Close-packed colloidal crystals are promising precursors for novel materials, but only after appropriate methods are developed to fix their structure. A wide range of advanced materials has recently been synthesized by replicating the structure of colloidal crystals into durable solid matrices. Such materials with structured pores have promise as photonic crystals, catalysts, and membranes, and in a variety of other

Orlin D. Velev; Abraham M. Lenhoff

2000-01-01

8

Photo-tuning of structural color of composite material consisting of inverse opal structure and azo-polymer liquid crystal  

NASA Astrophysics Data System (ADS)

A photochemically tunable structural color material was prepared by infiltration of the polymer liquid crystal (LC) having azo-chromophores in a SiO2 inverse opal structure. The SiO2 inverse opal film infiltrated with the polymer LC reflected a light, which is called a structural color, corresponding to the periodicity as well as the refractive indices of the inverse opal structure. Linearly polarized light irradiation caused the shift of the structural color band to longer wavelength more than 15 nm. This is caused by the formation of uniaxially anistorpic molecular orientation of the polymer LC. The switched state was stable under interior light, and reversible switching of the reflection band can be achieved by the linearly and circularly polarized light irradiation. This photoswitching property will be suitable for various optical materials such as memory, display so on.

Kurihara, S.; Moritsugu, M.; Kubo, Shoichi; Kim, Sun-nam; Ogata, Tomonari; Nonaka, Takamasa; Sato, Osamu

2007-10-01

9

Quasiparticle excitations in valence-fluctuation materials: effects of band structure and crystal fields  

SciTech Connect

Evidence is now quite strong that the elementary hybridization model is the correct way to understand the lattice-coherent Fermi liquid regime at very low temperatures. Many-body theory leads to significant renormalizations of the input parameters, and many of the band-theoretic channels for hybridization are suppressed by the combined effects of Hund's-rule coupling, crystal-field splitting, and the f-f Coulomb repulsion U. Some exploratory calculations based on this picture are described, and some inferences are drawn about the band structures of several heavy-fermion materials. These inferences can and should be tested by suitably modified band-theoretic calculations. We find evidence for a significant Baber-scattering contribution in the very-low-temperature resistivity. A new mechanism is proposed for crossover from the coherent Fermi-liquid regime to the incoherent dense-Kondo regime. 28 refs.

Brandow, B.H.

1985-01-01

10

The influence of material properties on the elastic band structures of one-dimensional functionally graded phononic crystals  

NASA Astrophysics Data System (ADS)

We study the influence of material parameters on elastic band gaps of one-dimensional functionally graded phononic crystals (FGPCs). By using plane-wave expansion, we calculate the first four band structures of FGPCs consisting of functionally graded materials (FGMs). These structures vary exponentially. We systematically study the influence of material parameters for four different FGPC models. Compared with traditional phononic crystals (PCs), the FGPC band gaps are clearly changed by FGMs. We also consider the influence of material composition, material properties and geometrical parameters on band gaps. Results show that different FGM properties can change the band structures remarkably. Our work can facilitate the design of vibration filters and noise insulators and provide more design freedom in engineering.

Su, Xing-liang; Gao, Yuan-wen; Zhou, You-he

2012-12-01

11

Ytterbium-doped apatite-structure crystals: A new class of laser materials  

SciTech Connect

A new class of Yb-lasers is summarized in this article. The apatite family of crystals, based on the hexagonal structure of the mineral fluorapatite, has been found to impose favorable spectroscopic and laser properties on the Yb[sup 3+] activator ion. Crystals of Yb-doped Ca[sub 5](PO[sub 4])[sub 3]F, Sr[sub 5](PO[sub 4])[sub 3]F, Ca[sub [ital x

Payne, S.A.; DeLoach, L.D.; Smith, L.K.; Kway, W.L.; Tassano, J.B.; Krupke, W.F. (Lawrence Livermore National Laboratory, University of California, P. O. Box 5508, Livermore, California 94550 (United States)); Chai, B.H.T.; Loutts, G. (Center for Research and Education in Optics and Lasers, University of Central Florida, Orlando, Florida 32826 (United States))

1994-07-01

12

Interference of electron diffracted beams from crystals and amorphous materials to measure their structure, mean inner potential and coherence properties  

Microsoft Academic Search

This talk presents electron interferograms of crystals and amorphous materials used to measure their structure, mean inner potential and the coherence properties of their quasiparticles such as phonons, plasmons and, hopefully in the future, magnons. Recent methods of k-space interference has revealed that practically all electron intensities on the diffraction plane of a modern TEM have sufficient coherence to produce

Rodney Herring

2010-01-01

13

Structural, thermal and optical characterization of an organic NLO materialBenzaldehyde thiosemicarbazone monohydrate single crystals  

NASA Astrophysics Data System (ADS)

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.

Santhakumari, R.; Ramamurthi, K.

2011-02-01

14

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

NASA Astrophysics Data System (ADS)

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.

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

2011-08-01

15

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

DOEpatents

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.

Yang, Jihui (Lakeshore, CA); Shi, Xun (Troy, MI); Bai, Shengqiang (Shanghai, CN); Zhang, Wenqing (Shanghai, CN); Chen, Lidong (Shanghai, CN); Yang, Jiong (Shanghai, CN)

2012-01-17

16

Olivine Crystal Structure  

NSDL National Science Digital Library

This exercise is based on recent crystallographic research on the olivine crystal structure published by Redfern et al. (2000). The authors of this study synthesized Fa50 olivine olivine (MgFeSiO4) in an experimental apparatus at temperatures ranging from 100 to 1250 °C, quenched the experiments, and used in situ neutron powder diffraction techniques to investigate changes in the synthesized olivines as a function of temperature. While this study reports cutting-edge materials research carried out with the latest crystallographic techniques, the results are educationally instructive and illustrate important concepts normally covered in an undergraduate mineralogy course. In this exercise, students are guided into the American Mineralogist Crystal Structure Database to retrieve and download published crystal structure data for viewing in either the CrystalMaker or XtalDraw visualization software packages. The students are instructed on how to manipulate the structures and are asked to plot some of the crystallographic data from this study on graphs using a spreadsheet program such as Excel.

Ratajeski, Kent

17

Band structure of photonic crystal with dispersive and lossy materials using Dirichlet-to-Neumann wave vector eigen equation method  

NASA Astrophysics Data System (ADS)

We present the Dirichlet-to-Neumann wave vector eigen equation (DtN-WVEE) method to calculate the band structure of photonic crystal (PhC) with dispersive and lossy materials, and then use finite-difference time-domain method to verify the validity of the results of the DtN-WVEE method. Since the material is lossy with a non-zero imaginary part of epsilon, the wave vector of PhC band structure also has a non-zero imaginary part which results in the reduction of the intensity of the mode. We further present the band structure which gives the relationship among the normalized frequency, the real part of the wave vector, and the imaginary part of the wave vector. To our knowledge, the band structure of lossy PhC has not been well studied yet, and our results can be useful in designing the devices using surface plasmon polariton effect.

Jiang, Bin; Zhang, Yejin; Wang, Yufei; Zheng, Wanhua

2012-08-01

18

On the misuse of the crystal structure model of the Ni electrode material  

NASA Astrophysics Data System (ADS)

Ni-Cd pocket plate single cells have been float-charged at 1.40 and 1.42 V at room temperature and 40C for a time period of 2-3 years. Subsequent ex situ X-ray diffraction measurements were performed on the charged positive active Ni electrode material. The appearance of the diffraction pattern of one of the charged electrode materials (conventionally named nickel oxy-hydroxide-?-NiOOH) shows resemblance to the pattern of discharged nickel hydroxide (?-Ni(OH) 2). In situ X-ray diffraction, electrochemical and transmission electron microscopy measurements were used to further investigate this charged phase. Our results clearly show the difficulties to interpret the data from X-ray powder diffraction measurements in order to study and characterise aged positive active material, especially in the charged state. The use of structure models from well crystalline, often synthetically manufactured, powder samples in order to describe amorphous material must be questioned. There are numerous parameters that may affect the charge/discharge transformation and the structural appearance of positive active material. Transmission electron microscopy (TEM) measurements indicate structural differences of the sample subjected to Rietveld refinement on X-ray diffraction data compared to earlier published structure.

Palmqvist, Ulrik; Eriksson, Lars; Garca-Garca, Javier; Simic, Nina; Ahlberg, Elisabet; Sjvall, Rune

19

New insights into the GdBaCo2O5+? material: Crystal structure, electrical and electrochemical properties  

NASA Astrophysics Data System (ADS)

Selected area electron diffraction (SAED) and high resolution transmission electron microscopy (HRTEM) studies reveal that the crystal structure and microstructure of GdBaCo2O5+? are highly influenced by the oxygen stoichiometry. In addition to layered-type ordering of the Ba and Gd atoms along the c-direction of the structure and location of anion vacancies within the (GdO)x planes giving a apנapנ2ap unit cell, two different perovskite related superstructures are observed. A superstructure with apנ3apנ2ap unit cell, probably due to extra ordering of the anion vacancies within the (GdO)x planes is formed for ? values close to 0.33 and a superstructure with ?2apנ?2bpנ2ap unit cell associated to tilting of the CoO6 octahedra appears for the compound with ? values close to 1. Domain formation with perpendicular orientations of the unit cell occurs in crystals with orthorhombic symmetry of the structure. Physical properties of the aforementioned material, which is well known as a potential candidate of cathode for intermediate temperature solid oxide fuel cells, are likely to be strongly affected by its oxygen stoichiometry and therefore by its crystal structure and microstructure.

Muoz-Gil, Daniel; Prez-Coll, Domingo; Pea-Martnez, Juan; Garcia-Martn, Susana

2014-10-01

20

Photonic Crystal Laser Accelerator Structures  

SciTech Connect

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.

Cowan, Benjamin M

2003-05-21

21

Liquid Crystal Materials and Liquid Crystal Displays  

Microsoft Academic Search

Since the early 1970s, three major prerequisites have brought the success of the liquid crystal display (LCD) technology to its key role of today. Namely, the discovery of electro-optical field-effects on which the displays are based, the successful search for liquid crystals (LCs) with material properties that meet the complex requirements of electro-optical effects and render the effects applicable in

Martin Schadt

1997-01-01

22

Photo-response properties of PBG composite material consisting of inverse opal structure and azo-polymer liquid crystal  

NASA Astrophysics Data System (ADS)

Photo-tunable PBG composite material was prepared by infiltration of the polymer liquid crystal (LC) having azo-chromophores in a SiO2 inverse opal structure. The SiO2 inverse opal film infiltrated with the polymer LC reflected a light, which is called Bragg diffraction, corresponding to the periodicity as well as the refractive indices of the inverse opal structure. Linearly polarized light irradiation caused the shift of the the Bragg diffraction band to longer wavelength more than 15 nm. This is caused by the formation of uniaxially anistorpic molecular orientation of the polymer LC. The switched state was stable under interior light, and reversible switching of the reflection band can be achieved by the linearly and circularly polarized light irradiation. This photoswitching property will be suitable for various optical materials such as memory, display so on.

Kurihara, S.; Moritsugu, M.; Kubo, Shoichi; Kim, Sun-nam; Ogata, Tomonari; Nonaka, Takamasa; Sato, Osamu

2007-10-01

23

Two inorganic-organic hybrid materials based on polyoxometalate anions and methylene blue: Preparations, crystal structures and properties  

SciTech Connect

Two novel inorganic-organic hybrid materials based on an organic dye cation methylene blue (MB) and Lindqvist-type POM polyanions, [C{sub 22}H{sub 18}N{sub 3}S]{sub 2}Mo{sub 6}O{sub 19} 2DMF (1) and [C{sub 22}H{sub 18}N{sub 3}S]{sub 2}W{sub 6}O{sub 19} 2DMF (2) were synthesized under ambient conditions and characterized by CV, IR spectroscopy, solid diffuse reflectance spectrum, UV-vis spectra in DMF solution, luminescent spectrum and single crystal X-ray diffraction. Crystallographic data reveal that compounds 1 and 2 are isostructural and both crystallize in the triclinic space group P1-bar . Their crystal structures present that the layers of organic molecules and inorganic anions array alternatively, and there exist strong {pi}...{pi} stacking interactions between dimeric MB cations and near distance interactions among organic dye cations, Lindqvist-type POM polyanions and DMF molecules. The solid diffuse reflectance spectra and UV-vis spectra in DMF solution appear new absorption bands ascribed to the charge-transfer transition between the cationic MB donor and the POM acceptors. Studies of the photoluminescent properties show that the formation of 1 and 2 lead to the fluorescence quenching of starting materials. -- Graphical abstract: Their crystal structures present that the layers of organic molecules and inorganic anions array alternatively, and there exist strong {pi}...{pi} stacking interactions between dimeric MB cations. Display Omitted

Nie Shanshan; Zhang Yaobin; Liu Bin; Li Zuoxi; Hu Huaiming [Key Laboratory of Synthetic and Natural Functional Molecule Chemistry (Ministry of Education), Shaanxi Key Laboratory of Physico-Inorganic Chemistry, Department of Chemistry, Northwest University, Xi'an 710069 (China); Xue Ganglin, E-mail: xglin707@163.co [Key Laboratory of Synthetic and Natural Functional Molecule Chemistry (Ministry of Education), Shaanxi Key Laboratory of Physico-Inorganic Chemistry, Department of Chemistry, Northwest University, Xi'an 710069 (China); Fu Feng; Wang Jiwu [Department of Chemistry, Yanan University, Yan'an 716000 (China)

2010-12-15

24

Materials and structures  

NASA Technical Reports Server (NTRS)

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.

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

25

Crystal Structures as Geobarometers  

NSDL National Science Digital Library

This exercise is based on the recent formulation of a geobarometer based on the crystal structure of clinopyroxene (Nimis, 1995; 1998; 1999). This method relates structural parameters (e.g., the volumes of the unit cell and the M1 polyhedron) to the pressure at which the mineral crystallizes within basic and ultrabasic magmas. students are guided into the American Mineralogist Crystal Structure Database to retrieve and download published crystal structure data for viewing in either the CrystalMaker or Xtaldraw visualization software packages. students are instructed on how to examine the structures to determine pressure-sensitive crystallographic parameters students are then asked a series of questions related to what they learn.

Ratajeski, Kent

26

New lead inorganic-organic hybrid microporous and layered materials: synthesis, properties, and crystal structures.  

PubMed

Two new lead(II) phosphonates, namely, Pb2[PMIDA]*1.5H2O (1) (H4PMIDA = H2O3PCH2N(CH2CO2H)2) and Pb(H2L) (2) (H4L = CH3N(CH2PO3H2)2), have been synthesized by hydrothermal reactions at 150 degrees C. Complex 1 crystallized in tetragonal P42/n with cell dimensions of a = 17.317(7) and c = 7.507(5) A and Z = 8. In complex 1, Pb(1) is 6-coordinated by chelation in a tetradentate fashion by a PMIDA ligand (3 O, 1 N) and two phosphonate oxygen atoms from neighboring Pb(PMIDA) units in a severely distorted octahedral geometry, whereas Pb(2) is 6-coordinated by 4 carboxylate and 2 phosphonate oxygen atoms also with a severely distorted octahedral environment. These two different types of Pb(II) ions are interconnected through bridging carboxylate and phosphonate groups, resulting in a 3D network with micropores, whose cavity is filled by lattice water molecules interlinked via hydrogen bonds. Each PMIDA ligand bridges with 8 Pb(II) ions (3 Pb(1) and 5 Pb(2)). Complex 2 is orthorhombic, P2(1)2(1)2(1), with a = 7.382(5), b = 7.440(6), and c = 30.75(2) A and Z = 8. The structure of 2 features a 2D double lead(II) phosphonate layer along the ab plane. Each lead(II) ion is 5-coordinated by five phosphonate oxygen atoms from four ligands in a distorted trigonal bipyramid geometry. These double layers are further interconnected via hydrogen bonds between the protonated and uncoordinated phosphonate oxygens along the c-axis. PMID:12425639

Mao, Jiang-Gao; Wang, Zhike; Clearfield, Abraham

2002-11-18

27

Derivative Crystal Structures  

Microsoft Academic Search

There exists a class of crystal structures which are derived from others by generalization. These are here designated derivative structures. A special case of derivative structure is the popular ``superstructure.'' The symmetry of a derivative structure is a subgroup of the symmetry of the basic structure. Here the term ``subgroup'' is used in a wider sense than common in mathematical

M. J. Buerger

1947-01-01

28

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

NASA Technical Reports Server (NTRS)

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.

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

2012-01-01

29

Crystal Lattice Structures  

NSDL National Science Digital Library

This site provides an index of common crystal lattice structures--arrangements of atoms in a crystalline substance. The structures are indexed by Strukturbericht designation, Pearson symbol, space group, and prototype. Each structure is illustrated and accompanied by a brief description. The structure graphics can be viewed online, downloaded for external viewing, or manipulated in virtual space using a Java applet.

30

Crystal growth, structural, optical, dielectric and thermal studies of an amino acid based organic NLO material: L-phenylalanine L-phenylalaninium malonate.  

PubMed

Good transparent single crystals of L-phenylalanine L-phenylalaninium malonate (LPPMA) have been grown successfully by slow evaporation technique from aqueous solution. Single crystal X-ray diffractometer was utilized to measure unit cell parameter and to confirm the crystal structure. The chemical structure of compound was established by FT-NMR technique. The vibrational modes of the molecules of elucidated from FTIR spectra. Its optical behaviour has been examined by UV-vis spectral analysis, which shows the absence of absorbance in the visible region. Thermal properties of the LPPMA crystal were carried out by thermo gravimetric analysis (TGA) and differential thermal analysis (DTA) techniques, which indicate that the material does not decompose before melting. The melting point of grown crystal was observed as 180C by melting point apparatus. The NLO property was confirmed by the powder technique of Kurtz and Perry. The dielectric behaviour of the sample was also studied for the first time. PMID:21943710

Prakash, M; Geetha, D; Caroline, M Lydia; Ramesh, P S

2011-12-01

31

Photonic crystals, amorphous materials, and quasicrystals  

NASA Astrophysics Data System (ADS)

Photonic crystals consist of artificial periodic structures of dielectrics, which have attracted much attention because of their wide range of potential applications in the field of optics. We may also fabricate artificial amorphous or quasicrystalline structures of dielectrics, i.e. photonic amorphous materials or photonic quasicrystals. So far, both theoretical and experimental studies have been conducted to reveal the characteristic features of their optical properties, as compared with those of conventional photonic crystals. In this article, we review these studies and discuss various aspects of photonic amorphous materials and photonic quasicrystals, including photonic band gap formation, light propagation properties, and characteristic photonic states.

Edagawa, Keiichi

2014-06-01

32

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.  

PubMed

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 623 mm(3)) 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 (1)H 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). PMID:23624038

Dinakaran, Paul M; Kalainathan, S

2013-07-01

33

Simulations of Photonic Crystal and Dielectric Structures  

SciTech Connect

Dielectric materials and photonic crystal structures have electromagnetic properties that could potentially offer great benefits for accelerators. Computer simulation plays a critical role in designing, understanding, and optimizing these structures, especially the non-intuitive photonic crystal structures for which there is no relevant zeroth-order analytic model.

Werner, G. R. [Center for Integrated Plasma Studies, University of Colorado, Boulder, CO 80309 (United States)

2010-11-04

34

Syntheses, crystal structures, thermal stabilities and luminescence of six M(II)-hydroxyphosphonoacetate materials  

NASA Astrophysics Data System (ADS)

Hydrothermal reactions of Zn II, Ba II or Co II ion with 2-hydroxyphosphonoacetic acid (H 3L) afforded six metal phosphonates, namely, [Zn 5(O 3PCH(OH)CO 2) 4(C 6H 9N 2) 2] ( 1), [(C 4H 12N 2)Zn 5(O 3PCH(OH)CO 2) 4(H 2O) 2] ( 2), [(C 3H 12N 2) 0.5Zn 5(HO 3PCH(OH)CO 2)(O 3PCH(OH)CO 2) 3(H 2O) 2]0.75H 2O ( 3), [BaZn 2(O 3P CH(OH)CO 2) 2] ( 4), [Ba(HO 3PCH(OH)CO 2)] ( 5) and [(NH 4) 2Co 7(HO 3PCH(OH) CO 2) 6(HPO 4) 2(H 2O) 6]4H 2O ( 6). In 1, zinc tetrahedra ([ZnO 4]) and octahedra ([ZnO 5N], [ZnO 6]) are bridged by 2-hydroxyphosphonoacetate with penta- and hexadendate modes into a hybrid layer, which is further pillared by the 3-picolylamines to form a 3D structure through Zn-N bonds and hydrogen bondings. Both 2 and 3 are 3D framework encapsulating piperazine and 1,2-propanediamine cations, respectively. In solids 4- 6, the cross-linkages of [ZnO 4], [BaO 10] and [CoO 6] polyhedral with 2-hydroxyphosphonoacetate form 3D frameworks. Solids 3 and 4 behave thermally stable up to 250 and 300 C under air atmosphere, respectively. It is interesting that the peak emission of solid 3 displays a 10 nm red-shift after simple heat-treatment.

Fu, Ruibiao; Hu, Shengmin; Wu, Xintao

2011-04-01

35

Syntheses, crystal structures, thermal stabilities and luminescence of six M(II)-hydroxyphosphonoacetate materials  

SciTech Connect

Hydrothermal reactions of Zn{sup II}, Ba{sup II} or Co{sup II} ion with 2-hydroxyphosphonoacetic acid (H{sub 3}L) afforded six metal phosphonates, namely, [Zn{sub 5}(O{sub 3}PCH(OH)CO{sub 2}){sub 4}(C{sub 6}H{sub 9}N{sub 2}){sub 2}] (1), [(C{sub 4}H{sub 12}N{sub 2})Zn{sub 5}(O{sub 3}PCH(OH)CO{sub 2}){sub 4}(H{sub 2}O){sub 2}] (2), [(C{sub 3}H{sub 12}N{sub 2}){sub 0.5}Zn{sub 5}(HO{sub 3}PCH(OH)CO{sub 2})(O{sub 3}PCH(OH)CO{sub 2}){sub 3}(H{sub 2}O){sub 2}].0.75H{sub 2}O (3), [BaZn{sub 2}(O{sub 3}P CH(OH)CO{sub 2}){sub 2}] (4), [Ba(HO{sub 3}PCH(OH)CO{sub 2})] (5) and [(NH{sub 4}){sub 2}Co{sub 7}(HO{sub 3}PCH(OH) CO{sub 2}){sub 6}(HPO{sub 4}){sub 2}(H{sub 2}O){sub 6}].4H{sub 2}O (6). In 1, zinc tetrahedra ([ZnO{sub 4}]) and octahedra ([ZnO{sub 5}N], [ZnO{sub 6}]) are bridged by 2-hydroxyphosphonoacetate with penta- and hexadendate modes into a hybrid layer, which is further pillared by the 3-picolylamines to form a 3D structure through Zn-N bonds and hydrogen bondings. Both 2 and 3 are 3D framework encapsulating piperazine and 1,2-propanediamine cations, respectively. In solids 4-6, the cross-linkages of [ZnO{sub 4}], [BaO{sub 10}] and [CoO{sub 6}] polyhedral with 2-hydroxyphosphonoacetate form 3D frameworks. Solids 3 and 4 behave thermally stable up to 250 and 300 {sup o}C under air atmosphere, respectively. It is interesting that the peak emission of solid 3 displays a 10 nm red-shift after simple heat-treatment. -- Graphical abstract: Six new metal phosphonates exhibit layered or 3D frameworks based on 2-hydroxyphosphonoacetate with five new coordination modes. Display Omitted Research highlights: {yields} Metal phosphonates are layered or 3D frameworks. {yields} Metal phosphonates are stable up to 250-300 {sup o}C under air atmosphere. {yields} 2-Hydroxyphosphonoacetate displays five new coordination modes.

Fu, Ruibiao; Hu, Shengmin [State Key Laboratory of Structural Chemistry, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Science, Fuzhou, Fujian 350002 (China); Wu, Xintao, E-mail: wxt@fjirsm.ac.c [State Key Laboratory of Structural Chemistry, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Science, Fuzhou, Fujian 350002 (China)

2011-04-15

36

A 3.90 V iron-based fluorosulphate material for lithium-ion batteries crystallizing in the triplite structure  

SciTech Connect

Li-ion batteries have empowered consumer electronics and are now seen as the best choice to propel forward the development of eco-friendly (hybrid) electric vehicles. To enhance the energy density, an intensive search has been made for new polyanionic compounds that have a higher potential for the Fe{sup 2+}/Fe{sup 3+} redox couple. Herein we push this potential to 3.90 V in a new polyanionic material that crystallizes in the triplite structure by substituting as little as 5 atomic per cent of Mn for Fe in Li(Fe{sub 1-{delta}}Mn{delta})SO{sub 4}F. Not only is this the highest voltage reported so far for the Fe{sup 2+}/Fe{sup 3+} redox couple, exceeding that of LiFePO{sub 4} by 450 mV, but this new triplite phase is capable of reversibly releasing and reinserting 0.7-0.8 Li ions with a volume change of 0.6% (compared with 7 and 10% for LiFePO{sub 4} and LiFeSO{sub 4}F respectively), to give a capacity of {approx}125 mA h g{sup -1}.

Barpanda, P.; Ati, M.; Melot, B.C.; Rousse, G.; Chotard, J-N.; Doublet, M-L.; Sougrati, M.T.; Corr, S.A.; Jumas, J-C.; Tarascon, J-M. (CNRS-UMR); (U. Kent)

2011-11-17

37

Crystal structure of daqingshanite  

Microsoft Academic Search

Daqinshanite, a new mineral recently discovered in China, is a kind of strontium-rare earth-bearing phosphate-carbonate. The\\u000a ideal formula is: (Sr, Ca, Ba), RF(PO4)(CO3)3. The mineral belongs to the trigonal system. The intensity data were collected with a single-crystal four-circle diffractometer.\\u000a The lattice parameters are given as:a=10.058(0.002) ;c=9.225(0.003) . Space group=R3m,Z=3. The crystal structure was solved by Patterson and electron density

Lulu Ximen; Zhizhong Peng

1985-01-01

38

Crystal structure, optical and thermal studies of a new organic nonlinear optical material: L-Histidinium maleate 1.5-hydrate  

SciTech Connect

Highlights: ? L-Histidinium maleate 1.5-hydrate, a new organic crystal has been grown for the first time. ? The crystal structure is reported for the first time (CCDC 845975). ? The crystal belongs to monoclinic system with space group P2{sub 1}, Z = 4, a = 11.4656(7) ?, b = 8.0530(5) ?, c = 14.9705(9) ? and ? = 101.657(2). ? The optical absorption study substantiates the complete transparency of the crystal. ? Kurtz powder SHG test confirms the nonlinear property of the crystal. -- Abstract: A new organic nonlinear optical material L-histidinium maleate 1.5-hydrate (LHM) with the molecular formula C{sub 10}H{sub 16}N{sub 3}O{sub 7.5} has been successfully synthesized from aqueous solution by slow solvent evaporation method. The structural characterization of the grown crystal was carried out by single crystal X-ray diffraction at 293(2) K. In the crystal, molecules are linked through inter and intramolecular N-H?O and O-H?O hydrogen bonds, generate edge fused ring motif. The hydrogen bonded motifs are linked to each other to form a three dimensional network. The FT-IR spectroscopy was used to identify the functional groups of the synthesized compound. The optical behavior of the grown crystal was examined by UVvisible spectral analysis, which shows that the optical absorption is almost negligible in the wavelength range 2801300 nm. The nonlinear optical property was confirmed by the powder technique of Kurtz and Perry. The thermal behavior of the grown crystal was analyzed by thermogravimetric analysis.

Gonsago, C. Alosious [Department of Physics, A. J. College of Engineering, Chennai 603103 (India)] [Department of Physics, A. J. College of Engineering, Chennai 603103 (India); Albert, Helen Merina [Department of Physics, Sathyabama University, Chennai 600119 (India)] [Department of Physics, Sathyabama University, Chennai 600119 (India); Karthikeyan, J. [Department of Chemistry, Sathyabama University, Chennai 600119 (India)] [Department of Chemistry, Sathyabama University, Chennai 600119 (India); Sagayaraj, P. [Department of Physics, Loyola College, Chennai 600034 (India)] [Department of Physics, Loyola College, Chennai 600034 (India); Pragasam, A. Joseph Arul, E-mail: drjosephsu@gmail.com [Department of Physics, Sathyabama University, Chennai 600119 (India)] [Department of Physics, Sathyabama University, Chennai 600119 (India)

2012-07-15

39

Crystal Lattice Structures  

NSDL National Science Digital Library

The US Naval Research Laboratories (NRL) maintains this Website containing 2-D images (HTML) of 78 crystal lattice structures (e.g., body-centered-cubic, hexagonal-close packed, carbon, silicon). The index of structures can be searched by Pearson Symbol, Space Group, or Strukturbericht Designation. On each page, the structure can be viewed from different perspectives, and information about atomic number, vector diagrams, and atom coordinates is available. The site also contains a bibliography and a programming information page, both with hyperlinks.

40

Optical materials: gold binary-structured arrays based on monolayer colloidal crystals and their optical properties (small 12/2014).  

PubMed

Gold binary-structured ordered arrays, built of the hexagonally arranged nanoshells and nanorings, are fabricated based on non-shadow deposition on dualistic monolayer colloidal crystal. On page 2374 W. Cai and colleagues show how such arrays exhibit tunable surface plasmon resonance properties of gold nanoshells and the strong electromagnetic field enhancement effects of gold nanorings, as well as a promising potential for the substrate of surface enhanced Raman scattering-based devices. PMID:24942763

Liu, Guangqiang; Li, Xinhua; Wang, Wenbo; Zhou, Fei; Duan, Guotao; Li, Yue; Xu, Zongke; Cai, Weiping

2014-06-01

41

Crystal Structure of Ettringite  

Microsoft Academic Search

ETTRINGITE (Ca6[Al(OH)6]2(SO4)3.26H2O) occurs as a natural mineral, and is technically important as a hydration product of Portland and supersulphated cements and in its use, as satin white, for coating paper. It forms hexagonal, prismatic crystals which in synthetic material are often highly elongated. Bannister, Hey and Bernal1 obtained unit-cell data (hexagonal: a 11.26, c 21.48 , space group P63\\/mmc, Z

A. Moore; H. F. W. TAYLOR

1968-01-01

42

Physicomechanical model of the elastoplastic properties of materials taking account of the structural levels of deformation and the kinetic properties of real crystals  

NASA Astrophysics Data System (ADS)

On the basis of an earlier-proposed translational-rotational model of a continuous medium, reflecting a hierarchy of structural levels of deformation and destruction, the influence of diverse temperature-velocity conditions of loading on the properties of materials is investigated. The applicability of the theory for the description of unified equations of the mechanical properties of crystals in nonsteady conditions of deformation is established. Analysis and comparison of the calculations results with experiment is undertaken for uniaxial loading.

Likhachev, V. A.; Malinin, V. G.

1984-09-01

43

PSSP, a Computer Program for the Crystal Structure Solution of Molecular Materials from X-ray Powder Diffraction Data  

SciTech Connect

This work describes the computer program PSSP (powder structure solution program) for the crystal structure solution of molecular solids from X-ray powder diffraction data. This direct-space structure solution program uses the simulated annealing global optimization algorithm to minimize the difference between integrated intensities calculated from trial models and those extracted in a Le Bail fit of the experimental pattern, using a cost function for dealing with peak overlap through defined intensity correlation coefficients, computationally faster to calculate than R{sub wp}. The methodology outlined is applicable to organic solids composed of moderately complex rigid and flexible molecules, using diffraction data up to relatively low resolution. PSSP performance tests using 11 molecular solids with six to 20 degrees of freedom are analyzed.

Pagola, S.; Stephens, P

2010-01-01

44

Frustrated polymer crystal structures  

NASA Astrophysics Data System (ADS)

Several crystal structures or polymorphs of chiral or achiral polymers and biopolymers with three fold conformation of the helix have been found to conform to a common and -with one exception(Puterman, M. et al, J. Pol. Sci., Pol. Phys. Ed., 15, 805 (1977))- hitherto unsuspected packing scheme. The trigonal unit-cell contains three isochiral helices; the azimuthal setting of one helix differs significantly from that of the other two, leading to a so-called frustrated packing scheme, in which the environment of conformationally identical helices differs. Two variants of the frustrated scheme are analyzed. Similarities with frustrated two dimensional magnetic systems are underlined. Various examples of frustration in polymer crystallography are illustrated via the elucidation or reinterpretation of crystal phases or polymorphs of polyolefins, polyesters, cellulose derivatives and polypeptides. Structural manifestations (including AFM evidence) and morphological consequences of frustration are presented, which help diagnose the existence of this original packing of polymers.(Work done with L. Cartier, D. Dorset, S. Kopp, T. Okihara, M. Schumacher, W. Stocker.)

Lotz, B.; Strasbourg, 67083

1997-03-01

45

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.

46

Transition metal complexes with oligopeptides: single crystals and crystal structures.  

PubMed

The coordination chemistry of short chain peptides with transition metals is described in terms of the available crystal structures. Despite their high interest as synthetic models for metalloproteins and as building blocks for molecular materials based on the tuneable properties of oligopeptides, single crystal X-ray diffraction studies are scarce. A perusal of the most relevant results in this field allows us to define the main characteristics of oligopeptide-metal interactions, the fundamental problems for the crystallization of these complexes, and some hints to identify future promising approaches to advance the development of metallopeptide chemistry. PMID:24874062

Lillo, Vanesa; Galn-Mascars, Jos Ramn

2014-07-14

47

From the molecular structure to spectroscopic and material properties: computational investigation of a bent-core nematic liquid crystal.  

PubMed

We present a computational investigation of the nematic phase of the bent-core liquid crystal A131. We use an integrated approach that bridges density functional theory calculations of molecular geometry and torsional potentials to elastic properties through the molecular conformational and orientational distribution function. This unique capability to simultaneously access different length scales enables us to consistently describe molecular and material properties. We can reassign (13)C NMR chemical shifts and analyze the dependence of phase properties on molecular shape. Focusing on the elastic constants we can draw some general conclusions on the unconventional behavior of bent-core nematics and highlight the crucial role of a properly-bent shape. PMID:24470302

Greco, Cristina; Marini, Alberto; Frezza, Elisa; Ferrarini, Alberta

2014-05-19

48

Research on space structure materials  

NASA Astrophysics Data System (ADS)

An overview of the research conducted on space structure materials is presented. Major characteristics required for materials used for spacecraft structures operated in space for a long time were studied in the following aspects: (1) large specific strength and specific elasticity; (2) excellent characteristics stability; (3) excellent size stability; (4) large damping factor; and (5) excellent space environment resistance. Plastic-Metal Composite (PMC) and Metal-Metal Composite (MMC), most prosperous materials for space structures, were studied. Additionally hardened polyimide to withstand 300 C was under development as the main structural material for the H-2 Orbiting Plane (HOPE), and thermoplastic resin and liquid crystal composite were studied. MMC was deemed to be more prosperous material than PMC because of the superiority in physical properties. Joint research on radiation resistance of space structure materials was being conducted in cooperation with Takasaki Establishment of the Japan Atomic Energy Research Institute.

Yudate, Kouzou; Shibuta, Shigeto; Morino, Yoshiki

1992-08-01

49

Single-Crystal Scintillation Materials  

Microsoft Academic Search

\\u000a \\u000a Scintillation materials are \\u000a \\u000a employed to detect x-ray and ?-ray photons or accelerated particles. Wide-bandgap semiconductor or insulator materials with ahigh degree of structural\\u000a perfection are suitable for this purpose. They must accomplish fast and efficient transformation of incoming high-energy photon\\/particles\\u000a to anumber of electronhole pairs collected in the conduction and valence bands, respectively, and their radiative recombination\\u000a at suitable luminescence

Martin Nikl; Anna Vedda; Valentin V. Laguta

2010-01-01

50

Structural materials and components  

NASA Technical Reports Server (NTRS)

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.

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

1982-01-01

51

Prototype electrostatic ground state approach to predicting crystal structures of ionic compounds: Application to hydrogen storage materials  

NASA Astrophysics Data System (ADS)

We have developed a procedure for crystal structure generation and prediction for ionic compounds consisting of a collection of cations and rigid complex anions. Our approach is based on global optimization of an energy functional consisting of the electrostatic and soft-sphere repulsive energies using Metropolis Monte Carlo (MMC) simulated annealing in conjunction with smoothing of the potential energy landscape via the distance scaling method. The resulting structures, or prototype electrostatic ground states (PEGS), are subsequently relaxed using first-principles density-functional theory (DFT) calculations to obtain accurate structural parameters and thermodynamic properties. This method is shown to produce the ground state structures of NaAlH4 and Mg(AlH4)2 , as well as the mixed cation alanate K2LiAlH6 . For LiAlH4 , the PEGS search produces a structure with a static DFT total energy equal to that of the experimentally observed structure; the latter is stabilized by vibrational contributions to the free energy. For mixed-valence hexa-alanates, XY AlH6 , where X=(Li,Na,K) , and Y=(Mg,Ca) , the PEGS method predicts six unsuspected structure types, which are not found in the existing structure databases. The PEGS search yields energies that are, on the average, better than the best database structures with the same number of atoms per unit cell, demonstrating the predictive power and usefulness of the PEGS structures. In addition to the recently synthesized LiMgAlH6 compound, we predict that LiCaAlH6 , NaCaAlH6 , and KCaAlH6 are also thermodynamically stable with respect to phase separation into other alanates and metal hydrides. In contrast, NaMgAlH6 and KMgAlH6 are slightly unstable (by less than 3kJ/mol ) relative to the phase separation into NaAlH4 , KAlH4 , and MgH2 . We suggest that solid-state ion-exchange reactions between X3AlH6 (X=Li,Na,K) and YCl2 (Y=Mg,Ca) could be used to synthesize the predicted mixed-valence hexa-alanates.

Majzoub, E. H.; Ozoli?, V.

2008-03-01

52

Crystal Structure Lab  

NSDL National Science Digital Library

This activity is concerned with crystals, the basic building units that make up rocks and minerals. Students construct a model of the silicon-oxygen tetrahedron and discover that the smallest whole unit that could form a unique crystal is called a unit cell. They learn that a unit cell would have all the properties of a large crystal such as a diamond, but would be only molecular size (submicroscopic). If a crystal starts to form from a slowly cooling magma or from a drying up pool of salty sea water, unit cells add themselves one on top of another in order to develop the large crystals we can see and handle.

Fetcho, Ray

53

Crystal structure of ZnWO(4) scintillator material in the range of 3-1423K.  

PubMed

The behaviour of the crystal structure of ZnWO(4) was investigated by means of synchrotron and neutron powder diffraction in the range of 3-300K. Thermal analysis showed the sample's melting around 1486K upon heating and subsequent solidification at 1442K upon cooling. Therefore, the structure was also investigated at 1423K by means of neutron diffraction. It is found that the compound adopts the wolframite structure type over the whole temperature range investigated. The lattice parameters and volume of ZnWO(4) at low temperatures were parametrized on the basis of the first order Grneisen approximation and a Debye model for an internal energy. The expansivities along the a-and b-axes adopt similar values and saturate close to 8 10(-6)K(-1), whereas the expansion along the c-axis is much smaller and shows no saturation up to 300K. The minimum expansivity corresponds to the direction close to the c-axis where edge-sharing linkages of octahedra occur. PMID:21693966

Trots, D M; Senyshyn, A; Vasylechko, L; Niewa, R; Vad, T; Mikhailik, V B; Kraus, H

2009-08-12

54

Crystal structure of ZnWO4 scintillator material in the range of 3-1423 K  

NASA Astrophysics Data System (ADS)

The behaviour of the crystal structure of ZnWO4 was investigated by means of synchrotron and neutron powder diffraction in the range of 3-300 K. Thermal analysis showed the sample's melting around 1486 K upon heating and subsequent solidification at 1442 K upon cooling. Therefore, the structure was also investigated at 1423 K by means of neutron diffraction. It is found that the compound adopts the wolframite structure type over the whole temperature range investigated. The lattice parameters and volume of ZnWO4 at low temperatures were parametrized on the basis of the first order Grneisen approximation and a Debye model for an internal energy. The expansivities along the a- and b-axes adopt similar values and saturate close to 8 10-6 K-1, whereas the expansion along the c-axis is much smaller and shows no saturation up to 300 K. The minimum expansivity corresponds to the direction close to the c-axis where edge-sharing linkages of octahedra occur.

Trots, D. M.; Senyshyn, A.; Vasylechko, L.; Niewa, R.; Vad, T.; Mikhailik, V. B.; Kraus, H.

2009-08-01

55

Directed Discovery of Crystal Structures  

NSDL National Science Digital Library

This contribution is modified from a published exercise "Directed Discovery of Crystal Structures Using Ball-and-Stick Models" [Mogk, 1997] . While the published exercise is based on student exploration of traditional ball-and-stick models of crystal structures, this modified version uses a similar "discovery-based" approach and the latest online crystallographic information and visualization software to teach the spatial relationships and crystal-chemical rules that govern the crystal structures of common minerals and crystalline solids. A few changes in the content have been made from the published exercise, mainly to accommodate the new digital media.

Mogk, Dave; Ratajeski, Kent

56

Crystallization and functionality of inorganic materials  

SciTech Connect

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.

Xue, Dongfeng, E-mail: dongfeng@ciac.jl.cn [State Key Laboratory of Rare Earth Resource Utilization, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022 (China) [State Key Laboratory of Rare Earth Resource Utilization, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022 (China); School of Chemical Engineering, Dalian University of Technology, Dalian 116024 (China); Li, Keyan [School of Chemical Engineering, Dalian University of Technology, Dalian 116024 (China)] [School of Chemical Engineering, Dalian University of Technology, Dalian 116024 (China); Liu, Jun [Key Laboratory of Low Dimensional Materials and Application Technology, Ministry of Education, Faculty of Materials, Optoelectronics and Physics, Xiangtan University, 411105 (China)] [Key Laboratory of Low Dimensional Materials and Application Technology, Ministry of Education, Faculty of Materials, Optoelectronics and Physics, Xiangtan University, 411105 (China); Sun, Congting; Chen, Kunfeng [State Key Laboratory of Rare Earth Resource Utilization, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022 (China) [State Key Laboratory of Rare Earth Resource Utilization, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022 (China); School of Chemical Engineering, Dalian University of Technology, Dalian 116024 (China)

2012-10-15

57

Crystal structure and chemistry of a complex indium phosphate framework material, (ethylenediammonium)In3P3O12(OH)2  

NASA Astrophysics Data System (ADS)

The chemistry and structure of a novel indium phosphate material (RIPS-4), (H3NCH2CH2NH3)In3-P3O12(OH)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 121242 ?m3 crystal in space group C2/m with a=18.662(4) , b=6.600(2) , c=12.573(3) and ?=120.92(1). The structure consists of a complex edge- and vertex-shared open framework of InO6 octahedra and PO4 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 (TiO2). This rutile edge-shared chain has its projecting oxygen atoms shared with the vertexes of either a PO4 tetrahedron or a second type of InO6 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.

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

2012-12-01

58

What can polymer crystal structure tell about polymer crystallization processes?  

NASA Astrophysics Data System (ADS)

Contrary to most or all other materials, crystallization of chiral but racemic polymers such as isotactic polypropylene is accompanied by a conformational rearrangement which leads to helical geometries: the building units of the crystal are helical stems, ? 10-20nm long, which can be either right-handed or left-handed. Helical hand cannot be reversed within the crystal structure: it is therefore a permanent marker and an indicator of molecular processes (in particular segregation/selection of helical hands) which take place during crystal growth, and more precisely during the crucial step of "efficient"helical stem deposition. The issue of proper helical hand selection during polymer crystal growth is mainly illustrated with isotactic polypropylene. Its various crystalline polymorphs (?, ?, ? and smectic) display virtually all possible combinations of helical hands, azimuthal settings and even non-parallel orientation of helix axes in space. Furthermore, a specific homoepitaxy which generates a lamellar branching in the ? phase "quadrites"and ?/? composite structures makes it possible a) to determine the helical hand and associated azimuthal setting of every stem in the crystalline entities and b) to determine the impact on the crystal structure and morphology of "mistakes"in helical hand of the depositing stem. Analysis of these morphologies demonstrates that the crystallization of isotactic polypropylene (and by implication of other achiral, helical polymers) is a highly sequential and "substrate-determined"process, i.e. that the depositing stem probes the topography of the growth face prior to attachment. These observations appear difficult to reconcile with crystallization schemes in which molecules (helical segments) are prearranged in a kind of pseudo-crystalline bundle (and as such, are not subjected to the high constraints of crystal symmetry) before deposition as a preassembled entity on the substrate.

Lotz, B.

2000-10-01

59

Structural materials and components  

NASA Technical Reports Server (NTRS)

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.

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

1983-01-01

60

Structural materials and components  

NASA Technical Reports Server (NTRS)

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.

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

1982-01-01

61

Crystals, Part II: Lattices and Structure.  

National Technical Information Service (NTIS)

Lists 715 domestic and foreign references added to the CFSTI collection during the period January 1959 through April 1965. Covers research on crystal lattices and lattice defects, crystal structure, crystal properties, optical properties, crystal processi...

1965-01-01

62

Thermal Expansion and Crystal Structure  

Microsoft Academic Search

In this investigation, the coefficients of thermal expansion of a number of crystals belonging to two structure types rutile and calcite have been studied by the x-ray method with a view to correlating thermal expansion with crystal structure. The crystals studied are MgF2, ZnF2, NiF2, MnF2, CoF2, FeF2, SnO2, PbO2, TiO2 (rutile), CrO2 and RuO2 belonging to the rutile type

K. V. Krishna Rao

1974-01-01

63

Synthetic thermoelectric materials comprising phononic crystals  

DOEpatents

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.

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

2013-08-13

64

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

NASA Astrophysics Data System (ADS)

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) , b=17.0104(18) , c=6.8528(7) , ?=100.6969(2), V=1345.1(2) 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) , c=4.6291(6) , V=564.34(10) 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).

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

2004-03-01

65

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

NASA Astrophysics Data System (ADS)

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) , b=6.2689(2) , and c=5.0042(2) 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.

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

2013-05-01

66

Fundamental Studies of Crystal Growth of Microporous Materials  

NASA Technical Reports Server (NTRS)

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.

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

2002-01-01

67

Interpreting intensities from white beam single-crystal Laue diffraction: A tool for structural characterization of Earth materials at extreme conditions.  

NASA Astrophysics Data System (ADS)

Monochromatic X-ray powder diffraction is the traditional method of choice for structural characterization of Earth material at extreme conditions of pressure and temperature. This method is intrinsically limited for such conditions due to the requirement for small sample volumes in order to attain very high pressure on the one hand and recrystallization at high temperature on the other hand, both of which are detrimental to powder statistics. The use of well established monochromatic single crystal diffraction as an alternative in such cases is often hampered by the lack of mobility and/or access of crystals within pressure devices. White beam Laue diffraction on static samples may offer a solution to this problem. This technique has already been exploited by the protein community mostly for time resolved measurements. It's application to small unit-cell inorganic materials is however complicated by the lack of data redundancy. The combination of white beam Laue diffraction with a micro-focused beam allows selectively probing individual crystallites within a diamond anvil cell (DAC) without the need to move the sample in the beam. However, to make this method a valid tool, a number of specific problems inherent to Laue diffraction have to be addressed. 1) Experimental geometry: Due to the nature of Laue diffraction, reciprocal space is covered mostly at high diffraction angles. This requires either a DAC with very wide opening or a set-up involving X-ray transparent gaskets. 2) energy specific absorption and Lorentz corrections: These can be done analytically and do not pose any serious problems. 3) harmonic overlap: Independent of symmetry and unit cell size, a significant fraction of observed reflections consist of two or more harmonic reflections, whose intensities need to be deconvoluted. This can be in principle solved using a lower energy threshold as offered by the Pilatus detector. Alternatives are deconvolution during refinement starting from non overlapped peaks, analogous to the Rietveld method in powder diffraction or - in the future - fully energy discriminating area detectors. A third alternative currently explored on the high-pressure beamline of the Advanced Light Source is step-scanning the monochromator across the available energy spectrum. 4) incident spectrum normalization: This is not straight forward since it is usually convoluted with detector response and cannot be easily measured. We found that comparing the measured intensities of a structurally well characterized crystal (e.g. calcite) with the calculated structure factor allows to establish a very satisfactory correction curve that includes both the variation in the flux and in the detector response. We will present details of procedures developed, together with examples of first structure solutions and refinements.

Kunz, M.; Tamura, N.; Dejoie, C.; Baerlocher, C.; McCusker, L.

2012-12-01

68

Fundamental Studies of Crystal Growth of Microporous Materials  

NASA Technical Reports Server (NTRS)

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.

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

2003-01-01

69

Nanoscale structure intercrystalline interactions in fat crystal networks  

Microsoft Academic Search

The functional attributes of fat-structured food products such as butter, margarine, chocolate, and ice cream are strongly influenced by the structure and physical properties of an underlying fat crystal network present in the material. Fat crystal networks are arranged in a hierarchical manner with characteristic and quantifiable nano and mesoscale structures. Recent studies carried out by our group have demonstrated

Nuria C. Acevedo; Fernanda Peyronel; Alejandro G. Marangoni

2011-01-01

70

Photonic Crystal HIDE Materials Engineering.  

National Technical Information Service (NTIS)

Milestone results have been achieved in the design, processing and testing of dielectric and metallodielectric composite materials for the control of IR emissivity. Our theoretical analyses have shown that an omnidirectional reflectivity band can be produ...

L. C. Kimerling

2001-01-01

71

Composite structural materials  

NASA Technical Reports Server (NTRS)

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.

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

1985-01-01

72

Composite structural materials  

SciTech Connect

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.

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

1985-08-01

73

Computational prediction of organic crystal structures and polymorphism  

NASA Astrophysics Data System (ADS)

The development of a robust manufacturing process for solid organic materials, such as pharmaceuticals, can be complicated when the molecules crystallize in different solid forms, including polymorphs. The diverse challenges to computational chemistry in computing the relative thermodynamic stability of different potential crystal structures for a range of organic molecules are outlined. Once the crystal structures which are thermodynamically feasible have been obtained, then comparison with the experimentally known polymorphs can provide interesting insights into crystallization behaviour. Although the computational prediction of polymorphism requires modelling the kinetic factors that can influence crystallization, the computational prediction of the crystal energy landscape is already a valuable complement to experimental searches for polymorphs.

Price, S. L.

74

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

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.

Broach, Robert W., E-mail: robert.broach@uop.com [UOP, a Honeywell Co., 50 E. Algonquin Rd., Des Plaines, IL 60017 (United States); Bedard, Robert L. [UOP, a Honeywell Co., 50 E. Algonquin Rd., Des Plaines, IL 60017 (United States)] [UOP, a Honeywell Co., 50 E. Algonquin Rd., Des Plaines, IL 60017 (United States); King, Lisa M., E-mail: lisa.king@uop.com [UOP, a Honeywell Co., 50 E. Algonquin Rd., Des Plaines, IL 60017 (United States); Pluth, Joseph J., E-mail: pluth@cars.uchicago.edu [The University of Chicago, Department of the Geophysical Sciences, Consortium for Advanced Radiation Sources, Chicago, IL 60637 (United States); The University of Chicago, The Materials Research Science and Engineering Center, Chicago, IL 60637 (United States); Smith, Joseph V. [The University of Chicago, Department of the Geophysical Sciences, Consortium for Advanced Radiation Sources, Chicago, IL 60637 (United States)] [The University of Chicago, Department of the Geophysical Sciences, Consortium for Advanced Radiation Sources, Chicago, IL 60637 (United States); Kirchner, Richard M., E-mail: richard.kirchner@manhattan.edu [Manhattan College, Chemistry Department, Bronx, NY 10471 (United States)

2012-12-15

75

Making Matter: The Atomic Structure of Materials  

NSDL National Science Digital Library

The Institut Laue Langevin provides the Making Matter: The Atomic Structure of Materials Website. This site offers information as well as 3D structures of inorganic materials (such as salt) in the Inorganic Crystal Structure Database. Sections included at the site are Close Packing, Compounds, Bonding, and Gems & Minerals, among others. This site provides spectacular 3D images (.gif and VRML format) of inorganic materials and is well worth the visit.

76

Manipulating the Crystal Growth of Organic Energetic Materials on Substrates  

NASA Astrophysics Data System (ADS)

Organic energetic materials (OMEs) have been attracted a lot of attention due to its wide application in military weapon. One of the most compelling researches is manipulating the crystal structure of OEMs due to their performances, such as ignition and burning rate, which depend strongly on the crystalline structure. The crystalline structure of OEMs on substrates has strong dependence on the experimental parameters, such as the deposition rate and external factors. This report demonstrates a new technique for manipulating the crystal growth of OEMs on substrates by micro-contact printing. The methodology depends on coating a polymer stamp with a surfactant, which has a strong affinity for the OEMs deposited on the substrate. The coated stamp selectively removes OEMs in contact areas when the stamp was lifted. And then the OEMs that were left on the substrates grew to the crystals. By careful choice facile film preparation method and optimal stamp pattern, this technique provides a new methodology for fabricating OEMs crystals from hexagon single crystals, dendrite crystals to micro-rod crystals and manipulating the size and distribution of these crystals.

Zhang, Xin; Zhang, Gengxin; Weeks, Brandon

2012-10-01

77

Composite structural materials. [aircraft structures  

NASA Technical Reports Server (NTRS)

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.

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

1980-01-01

78

Composite structural materials  

NASA Technical Reports Server (NTRS)

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.

Loewy, R.; Wiberley, S. E.

1986-01-01

79

Photonic Crystal Laser-Driven Accelerator Structures  

SciTech Connect

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.

Cowan, Benjamin M.

2007-08-22

80

Crystal Structure of Bi  

SciTech Connect

The room temperature structures of the two-layer Aurivillius phases Bi{sub 2.5}Me{sub 0.5}Nb{sub 2}O{sub 9} (Me=Na, K) have been refined with the Rietveld method from powder neutron diffraction data ({lambda}=1.470 {angstrom}). They consist of (Bi{sub 2}O{sub 2}){sup 2+} layers interleaved with perovskite (Bi{sub 0.5}Me{sub 0.5}Nb{sub 2}O{sub 7}){sup 2-} (Me=Na, K) slabs. The structures were refined in the orthorhombic space group A2{sub 1}am, Z=4, and the unit cell parameters of the two oxides are a= 5.4937(3), b=5.4571(4), c=24.9169(14) {angstrom} and a=5.5005(8), b=5.4958(8), c=25.2524(16) {angstrom}, respectively. The orthorhombic distortion increases with decreasing Me+ cation size in the perovskite layer (Bi/Me){sup 2+} site and the lone pair electrons from the Bi{sup 3+} cation are influencing the site distortion. This is in agreement with other two-layer Aurivillius phases and originates from bonding requirements depending on size and electronic environment.

Borg, Stefan; Svensson, Goeran

2001-02-15

81

Structure of NiCrAlY coatings deposited on single-crystal alloy turbine blade material by laser cladding  

Microsoft Academic Search

In the present work single and multiple layer NiCrAlY coatings were produced by laser cladding on (100) single-crystalline substrates of SRR99 Ni-based superalloy. Detailed structural characterisation and texture analysis by optical microscopy, scanning electron microscopy, X-ray diffraction and Rutherford backscattering showed that the NiCrAlY coatings consisted essentially of ? phase with yttrium oxide (Y2O3) and a small proportion of yttriumaluminum

R. Vilar; E. C. Santos; P. N. Ferreira; N. Franco; R. C. da Silva

2009-01-01

82

Composite structural materials  

NASA Technical Reports Server (NTRS)

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.

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

1978-01-01

83

The crystal structure and crystal chemistry of fernandinite and corvusite  

USGS Publications Warehouse

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

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

1994-01-01

84

Materials of construction for silicon crystal growth  

NASA Technical Reports Server (NTRS)

The performance of materials for construction and in contact with molten silicon for crystal growth is presented. The basis for selection considers physical compatibility, such as thermal expansion and strength, as well as chemical compatibility as indicated by contamination of the silicon. A number of new high technology materials are included as well as data on those previously used. Emphasis is placed on the sources and processing of such materials in that results are frequently dependent on the way a material is prepared as well as its intrinsic constituents.

Leipold, M. H.; Odonnell, T. P.; Hagan, M. A.

1980-01-01

85

The Surface Structure of Ground Metal Crystals  

NASA Technical Reports Server (NTRS)

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).

Boas, W.; Schmid, E.

1944-01-01

86

Crystal structure and multicomponent effects in Li1+xMn2-x-yAlyO4 cathode materials for Li-ion batteries  

NASA Astrophysics Data System (ADS)

Li, Al co-doped LiMn2O4 (Li1+xMn2-x-yAlyO4, 0?x?0.12, 0?y?0.1) cathode has been synthesized via a solid-state reaction designedly using industrial raw materials in bulk scale (>20kg). The multicomponent substitution effects on the crystal structures are examined systematically by Rietveld refinement of X-ray diffraction, and the resultant electrochemical properties for Li-ion batteries are also evaluated by galvanostatic charge-discharge and electrochemical impedance spectroscopy measurements. As a result, Li, Al co-doping significantly changes the unit cell parameter and atomic arrangement. With the increasing of doping levels, a cell dimension contracts with concomitant changes in bond length, whereby the MO6 octahedron (M=Mn/Li/Al) shrinks to provide structural integrity and the LiO4 tetrahedron expands to facilitate a fast electrochemical process. The strong spinel-framework contributes to a better structure-stabilization, resulting in a superior capacity retention ratio of 90% after 200 cycles at 0.5C at 55C for the optimized composition (Li1.06Mn1.86Al0.08O4), which possesses an initial value of 102mAhg-1. Meanwhile, the expansion of LiO4 tetrahedron leads to better high-rate performance, bringing about a capacity of 88mAhg-1 upon cycling at 10C at 55C. Further, Li1.06Mn1.86Al0.08O4 displays lower impedance than that of the pristine LiMn2O4.

Yu, Fu-Da; Wang, Zhen-Bo; Chen, Fei; Wu, Jin; Zhang, Xiao-Gang; Gu, Da-Ming

87

American Mineralogist Crystal Structure Database  

NSDL National Science Digital Library

This database provides access to information on every crystal structure published in the American Mineralogist, the Canadian Mineralogist, European Journal of Mineralogy, and Physics and Chemistry of Minerals, as well as selected datasets from other journals. The data are searchable by mineral name, author, chemistry, cell parameters and symmetry, diffraction pattern, and a general search. There are also lists of minerals represented in the database and authors of publications cited.

Downs, R. T.; Hall-Wallace, M.

88

Structural Materials: 95. Concrete  

SciTech Connect

Nuclear power plant concrete structures and their materials of construction are described, and their operating experience noted. Aging and environmental factors that can affect the durability of the concrete structures are identified. Basic components of a program to manage aging of these structures are identified and described. Application of structural reliability theory to devise uniform risk-based criteria by which existing facilities can be evaluated to achieve a desired performance level when subjected to uncertain demands and to quantify the effects of degradation is outlined. Finally, several areas are identified where additional research is desired.

Naus, Dan J [ORNL

2012-01-01

89

Composite structural materials  

NASA Technical Reports Server (NTRS)

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.

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

1984-01-01

90

American Mineralogist Crystal Structure Database  

NSDL National Science Digital Library

The American Mineralogist Crystal Structure Database website, maintained by the Mineralogical Society of America and the Mineralogical Association of Canada and sponsored by the National Science Foundation, "includes every structure published in the American Mineralogist, The Canadian Mineralogist, and the European Journal of Mineralogy." The authors are also currently adding data from Physics and Chemistry of Minerals. Users can search the data by minerals, authors, chemistry, cell parameter and symmetry, or by a simple general search. This no frills website allows users to easily find and download data.

91

Computational studies of crystal structure and bonding.  

PubMed

The analysis, prediction, and control of crystal structures are frontier topics in present-day research in view of their importance for materials science, pharmaceutical sciences, and many other chemical processes. Computational crystallography is nowadays a branch of the chemical and physicals sciences dealing with the study of inner structure, intermolecular bonding, and cohesive energies in crystals. This chapter, mainly focused on organic compounds, first reviews the current methods for X-ray diffraction data treatment, and the new tools available both for quantitative statistical analysis of geometries of intermolecular contacts using crystallographic databases and for the comparison of crystal structures to detect similarities or differences. Quantum chemical methods for the evaluation of intermolecular energies are then reviewed in detail: atoms-in-molecules and other density-based methods, ab initio MO theory, perturbation theory methods, dispersion-supplemented DFT, semiempirical methods and, finally, entirely empirical atom-atom force fields. The superiority of analyses based on energy over analyses based on geometry is highlighted, with caveats on improvised definitions of some intermolecular chemical bonds that are in fact no more than fluxional approach preferences. A perspective is also given on the present status of computational methods for the prediction of crystal structures: in spite of great steps forward, some fundamental obstacles related to the kinetic-thermodynamic dilemma persist. Molecular dynamics and Monte Carlo methods for the simulation of crystal structures and of phase transitions are reviewed. These methods are still at a very speculative stage, but hold promise for substantial future developments. PMID:21506002

Gavezzotti, Angelo

2012-01-01

92

Composite structural materials  

NASA Technical Reports Server (NTRS)

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.

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

1979-01-01

93

Composite structural materials  

NASA Technical Reports Server (NTRS)

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.

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

1984-01-01

94

Crystal structure, superconductivity and magnetism of the quasi-2D heavy fermion materials CeTIn[sub 5] (T = Co, Rh, Ir).  

SciTech Connect

The crystal structure of the recently discovered heavy-fermion (HF) superconductor CeCoIn{sub 5} (T{sub c} = 2.3 K) has been determined by high-resolution neutron powder diffraction. It is tetragonal (space group P4/mmm), with lattice parameters a = 4.61292(9) {angstrom} and c = 7.5513(2) {angstrom} at ambient conditions. Whereas CeCoIn{sub 5} is isostructural with the HF aniferromagnet CeRhIn{sub 5} and the HF superconductor CeIrIn{sub 5}, its cell constants and its only variable positional parameter, zIn2, differ significantly from the corresponding ones of CeRhIn{sub 5} and CeIrIn{sub 5}. As a result, the distortions of the cuboctahedron [CeIn{sub 3}], which is the key structural unit in all three materials, are different in CeCoIn{sub 5} from the ones in CeRhIn{sub 5} and CeIrIn{sub 5}. The compounds CeCoIn{sub 5} and CeIrIn{sub 5}, which contain the most distorted (in one or another way) [CeIn{sub 3}] cuboctahedra exhibit superconductivity at ambient pressure below 2.3 K and 0.4 K, respectively. On the other hand, CeRhIn{sub 5}, in which [CeIn{sub 3}] cuboctahedra are the less distorted, and the cubic HF CeIn{sub 3} are antiferromagnets at ambient pressure with T{sub N} = 3.8 K and 10 K respectively; they become superconductors under pressure of 16 kbar and 25 kbar with T{sub c} = 2.1 and 0.2 K respectively.

Sarrao, John L.,; Pagliuso, P. J. (Pascoal J.); Moreno, N. O.; Thompson, J. D. (Joe David); Fisk, Zachary; Moshopoulou, E. G.

2001-01-01

95

The crystal structure of dynamin  

PubMed Central

Dynamin-related proteins (DRPs) are multi-domain GTPases that function via oligomerization and GTP-dependent conformational changes to play central roles in regulating membrane structure across phylogenetic kingdoms. How DRPs harness self-assembly and GTP-dependent conformational changes to remodel membranes is not understood. Here we present the crystal structure of an assembly-deficient mammalian endocytic DRP, dynamin 1, lacking the proline-rich domain, in its nucleotide-free state. The dynamin 1 monomer is an extended structure with the GTPase domain and bundle signalling element positioned on top of a long helical stalk with the pleckstrin homology domain flexibly attached on its opposing end. Dynamin 1 dimer and higher order dimer multimers form via interfaces located in the stalk. Analysis of these interfaces provides insight into DRP family member specificity and regulation and provides a framework for understanding the biogenesis of higher order DRP structures and the mechanism of DRP-mediated membrane scission events.

Ford, Marijn G. J.; Jenni, Simon; Nunnari, Jodi

2014-01-01

96

Shear induced structures in crystallizing cocoa butter  

Microsoft Academic Search

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

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

2004-01-01

97

Making Matter: The atomic structure of materials  

NSDL National Science Digital Library

This site offers information as well as 3D images (gif and vrml) of the structures of inorganic materials (such as salt) in the Inorganic Crystal Structure Database. Sections included at the site are Close Packing, Compounds, Bonding, and Gems & Minerals, among others.

Hewat, Alan

2003-10-10

98

Three-Dimensional Photonic Crystal Laser-Driven Accelerator Structures  

SciTech Connect

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.

Cowan, B.; /SLAC

2006-09-07

99

Composite structural materials  

NASA Technical Reports Server (NTRS)

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.

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

1982-01-01

100

Materials and structures technology  

NASA Technical Reports Server (NTRS)

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.

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

1979-01-01

101

Crystal Structure of Human ?-Galactosidase  

PubMed Central

GM1 gangliosidosis and Morquio B are autosomal recessive lysosomal storage diseases associated with a neurodegenerative disorder or dwarfism and skeletal abnormalities, respectively. These diseases are caused by deficiencies in the lysosomal enzyme ?-d-galactosidase (?-Gal), which lead to accumulations of the ?-Gal substrates, GM1 ganglioside, and keratan sulfate. ?-Gal is an exoglycosidase that catalyzes the hydrolysis of terminal ?-linked galactose residues. This study shows the crystal structures of human ?-Gal in complex with its catalytic product galactose or with its inhibitor 1-deoxygalactonojirimycin. Human ?-Gal is composed of a catalytic TIM barrel domain followed by ?-domain 1 and ?-domain 2. To gain structural insight into the molecular defects of ?-Gal in the above diseases, the disease-causing mutations were mapped onto the three-dimensional structure. Finally, the possible causes of the diseases are discussed.

Ohto, Umeharu; Usui, Kimihito; Ochi, Toshinari; Yuki, Kenjiro; Satow, Yoshinori; Shimizu, Toshiyuki

2012-01-01

102

Open-Structured Materials: Skutterudites and Clathrates  

NASA Astrophysics Data System (ADS)

There are a large number of inorganic compounds with open-framework structures that entrap atoms or molecules within the lattice. Of these, the skutterudites and type I clathrates have gained the greatest attention from the perspective of thermoelectric applications. The crystal structure of these materials can be considered as being open in the sense that they possess voids whereby interstitially placed atoms are bounded loosely, thereby creating localized disorder in an otherwise well-ordered, covalently bonded lattice. The optimum situation occurs if the intrinsic mobility is relatively high due to the well-ordered, periodic structure of the crystal framework while the phonons are scattered by localized disorder. Substantial experimental and theoretical research has been devoted to these two material systems over the past decade. This effort has shown that the physical properties are directly related to their unique crystal structures, as well as the different compositions that can be synthesized in order to modify these physical properties.

Nolas, G. S.; Lin, X.; Martin, J.; Beekman, M.; Wang, H.

2009-07-01

103

American Mineralogist Crystal Structure Database  

NSDL National Science Digital Library

This database includes the crystal structure for every mineral published in the American Mineralogist, The Canadian Mineralogist, European Journal of Mineralogy and Physics, and Chemistry of Minerals. Data is now being imported from Acta Crystallographica as well. The database is maintained under the care of the Mineralogical Society of America and the Mineralogical Association of Canada. The data can be displayed or downloaded and are searchable by mineral, author, mineral chemistry, unit cell parameters and symmetry, diffraction pattern, or a general search. Links are provided to additional information and to crystallographic software.

104

The crystal structure of levyne  

Microsoft Academic Search

Summary Levyne, Ca27Na07K02[Al63Si117O36] 16.7 H2O, is rhombohedral, space group\\u000a$$R\\\\bar 3m$$\\u000a,ahex=13.338 andchex=23.014 . Its crystal structure is built up of layers of single and double six-membered rings of (Si, Al) O4 tetrahedra stacked according the model suggested fifteen years ago byBarrer andKerr. Cations are all disposed along the symmetry axis inside the levyne cage. One particular site is

S. Merlino; E. Galli; A. Alberti

1975-01-01

105

Novel Microstructures for Polymer-Liquid Crystal Composite Materials  

NASA Technical Reports Server (NTRS)

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.

Magda, Jules J.

2004-01-01

106

Nonlinear Phononic Periodic Structures and Granular Crystals.  

National Technical Information Service (NTIS)

In this chapter we describe the dynamic response of nonlinear phononic structures, focusing on granular crystals as the most prominent example. The chapter begins with a brief history of nonlinear lattices and with an introduction to granular crystals. It...

C. Daraio G. Theocharis N. Boechler

2012-01-01

107

The structural consequences of calcium crystal deposition.  

PubMed

Calcium pyrophosphate dihydrate and basic calcium phosphate (BCP) crystals are the most common calcium-containing crystals associated with rheumatic disease. Clinical manifestations of calcium crystal deposition include acute or chronic inflammatory and degenerative arthritides and certain forms of periarthritis. The intra-articular presence of BCP crystals correlates with the degree of radiographic degeneration. Calcium crystal deposition contributes directly to joint degeneration. Vascular calcification is caused by the deposition of calcium hydroxyapatite crystals in the arterial intima. These deposits may contribute to local inflammation and promote further calcification, thus aggravating the atherosclerotic process. Calcium crystal deposition results in substantial structural consequence in humans. PMID:24703349

Durcan, Laura; Bolster, Ferdia; Kavanagh, Eoin C; McCarthy, Geraldine M

2014-05-01

108

Spectroscopic, thermal and structural studies on manganous malate crystals  

NASA Astrophysics Data System (ADS)

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.

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

2013-01-01

109

Materials/structures testing  

NASA Astrophysics Data System (ADS)

An overview of the materials/structures test methodology used in the development of hypersonic vehicle components is presented. Focus is on aerothermal methodology and weather/erosion testing. For the latter, testing techniques which evaluate particle impact effects on vehicles operating at supersonic through hypersonic speeds in particle laden environments are described. Such facilities for increasing velocities are: wind tunnels/sleds; arc facilities; aeroballistic ranges. It is noted that it is of particular importance to demonstrate that flight components such as leading edges, cowl lips, and structural panels will survive the aerothermal flight environment. Specific components can experience very high heating rates and surface temperatures from 1100 to 1950 C.

Matthews, R. K.

110

Crystal orientation of non-magnetic materials by imposition of a high magnetic field  

Microsoft Academic Search

From the view point of learning from the nature, the controlling of crystal orientation is accounted to be a major subject for materials processing. This paper reviews the researches on the crystal orientation by use of a high magnetic field and belongs to the category of researches for mimicking structures, namely the crystal orientation, which nature or living bodies are

Shigeo Asai; Ken-suke Sassa; Masahiro Tahashi

2003-01-01

111

Negative refraction and focusing analysis in a left-handed material slab and realization with a 3D photonic crystal structure  

Microsoft Academic Search

The increasing interest in metamaterials and structures with negative refraction index requires a formulation capable of a full analysis of wave propagation in such materials and structures. Since two-dimensional (2D) problems have been largely explored in the literature, the natural step is a three-dimensional (3D) formulation of these structures. In this paper, (3D) formulation and simulation of a left-handed metamaterial

Majid Ahmadlou; Mahmoud Kamarei; Mohammad Hossein Sheikhi

2006-01-01

112

Composite structural materials  

NASA Technical Reports Server (NTRS)

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.

Loewy, Robert G.; Wiberley, Stephen E.

1987-01-01

113

Artificially structured magnetic materials  

SciTech Connect

This document reports the progress made during the first six months of the current three-year DOE grant on Artificially Structured Magnetic Materials.'' However, because some of the results of our previous three-year DOE grant on Artificially Structured Superconductors'' continue to emerge, both topics are addressed in this Progress Report. This report describes progress with DOE funding during the current calendar year; description of the research to be conducted during the remaining six months of the current grant year; a description of the status of the graduate students working on this research; lists of the invited talks, seminars and colloquia, of other recognition of our research, and of the publications crediting DOE sponsorship; and a summary of current and pending federal support. Since the research proposed to be conducted during the next 2 1/2 years is described in detail in our DOE proposal, it is only briefly reviewed here.

Falco, C.M.

1990-09-28

114

Beyond crystals: the dialectic of materials and information  

PubMed Central

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.

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

2012-01-01

115

Beyond crystals: the dialectic of materials and information.  

PubMed

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

Cartwright, Julyan H E; Mackay, Alan L

2012-06-28

116

Ultra-small footprint photonic crystal lasers with organic gain material  

NASA Astrophysics Data System (ADS)

We present the design of an optimized mixed-order photonic crystal laser structure. The lasing properties of this two-dimensional photonic crystal structure with an organic gain material are investigated theoretically and experimentally. A feedback structure fabricated in a thin film of Ta2O5 increases both the index contrast from the gain material as well as the optical confinement. Furthermore, by combining first order photonic crystal structures with second order ones losses occurring at the edge of the second order structure are dramatically reduced leading to a lower laser threshold and / or to a much smaller footprint of the laser.

Baumann, Kristian; Moll, Nikolaj; Stferle, Thilo; Wahlbrink, Thorsten; Bolten, Jens; Mollenhauer, Thomas; Moormann, Christian; Wang, Baoling; Scherf, Ulli; Mahrt, Rainer F.

2008-05-01

117

Phase-Field Crystal Modeling of Polycrystalline Materials  

NASA Astrophysics Data System (ADS)

In this thesis, we use and further develop the phase-field crystal (PFC) method derived from classical density functional theory to investigate polycyrstalline materials. The PFC method resolves atomistic scale processes by tracking the evolution of the local time averaged crystal density field, thereby naturally describing dislocations and grian boundaries (GBs), but with a phenomenological incorporation of vacancy diffusion that accesses long diffusive time scales beyond the reach of MD simulations. We use the PFC method to investigate two technologically important classes of polycrystalline materials whose properties are strongly influenced by GB equilibrium and non-equilibrium properties. The first are structural polycyrstalline materials such as nickel based superalloys used for turbine blades. Those alloys can develop large defects known as "hot tears'' due to the lack of complete crystal cohesion and strain localization during the late stages of solidification. We investigate the equilibrium structure of symmetric tilt GBs at high homologous temperatures and identify a wide range of misorientation that leads to the formation of nanometer-thick intergranular films with liquid like properties. The phase transition character of this "GB premelting'' phenomenon is investigated through the quantitative computation of a disjoining thermodynamic potential in both pure materials and alloys, using body-centered-cubic Fe as a model system. The analysis of this potential sheds light on the physical origin of attractive and repulsive forces that promote and suppress crystal cohesion, respectively, and are found to be strongly affected by solute addition. Our equilibrium studies also reveal the existence of novel structural transitions of low angle GBs driven by the pairing of dislocations with both screw and edge character. Non-equilibrium PFC simulations in turn characterize the response of GBs to an applied shear stress, showing that intergranular liquid-like films promote GB sliding and strain localization underlying hot tearing. The second class of polycrystalline materials investigated are nanocrystalline materials with a grain size less than a few hundred nanometers. Those materials exhibit desirable properties that include high strength and corrosion resistance. In order to understand basic mechanisms that control the thermal and mechanical stability of nanocrystalline materials, we investigate the stress-driven motion of GBs over a complete range of GB bicrystallography, which includes asymmetrical tilt boundaries with non-vanishing misorientation and inclination angles. We show that asymmetrical GBs exhibit coupled motion to a shear stress parallel to the GB plane and identify a wealth of different dislocation mechanisms mediated by glide, climb, and dislocation reactions, which underlie this coupled motion. We also show that asymmetrical GBs exhibit sliding due to the existence of discontinuous transitions between different coupling modes. Importantly, unlike sliding of symmetrical GBs promoted by GB premelting, sliding of asymmetrical GBs can exist at low temperature, thereby providing an important mechanism for the stress-driven evolution of nanocrystalline structures. In addition to the above studies of polycrystalline materials, we also use the PFC method as a theoretical framework for investigating the grain coarsening dynamics of polycrystalline structures in a broad class of systems that form crystal lattices through self-organization or self-assembly, including driven non-equilibrium systems, modulated phases of macromolecular systems such as diblock copolymers, and colloidal crystals. Our studies reveal that grain growth in those systems is governed by an entirely different dissipation mechanism than in polycrystalline materials. While the rate of curvature-driven grain growth in polycrystalline materials is well-known to be limited by interface dissipation, we find that bulk dissipation associated with lattice translation dramatically slows down grain coarsening in self- organized or assembled la

Adland, Ari Joel

118

The Materials in Your New TV: The Liquid Crystal Display  

NSDL National Science Digital Library

This module introduces the liquid crystal display, including glass substrates, electronics and liquid crystals. Learning objectives include explaining the components of the LCD system, describing the process of making LCD glass, illustrating a typical glassy structure, defining a liquid crystal, and discussing the applications of liquid crystal displays. The lesson requires one class period.

Stoebe, Thomas G.; Weeks, Margaret D.

2011-09-20

119

Crystal structure analysis of intermetallic compounds  

NASA Technical Reports Server (NTRS)

Study concerns crystal structures and lattice parameters for a number of new intermetallic compounds. Crystal structure data have been collected on equiatomic compounds, formed between an element of the Sc, Ti, V, or Cr group and an element of the Co or Ni group. The data, obtained by conventional methods, are presented in an easily usable tabular form.

Conner, R. A., Jr.; Downey, J. W.; Dwight, A. E.

1968-01-01

120

Photonic Crystal Laser-Driven Accelerator Structures  

SciTech Connect

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.

Cowan, B.; /SLAC

2005-09-19

121

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

NASA Astrophysics Data System (ADS)

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.

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

2012-09-01

122

Crystallization media inhibit protein structural dynamics  

NASA Astrophysics Data System (ADS)

The first role of any crystallization solution is to reduce the solubility of proteins, so that it induces protein precipitation. Most times, protein precipitation does not lead to protein crystallization. Do crystallization solutions play any other roles that are crucial for protein crystallization? Here we report our studies that crystallization solutions suppress or inhibit protein structural dynamics. Photoactive yellow protein (PYP), a bacterial blue light photoreceptor protein, is employed as a model system in our study. We use time-resolved FTIR spectroscopic technique to probe the structural dynamics of proteins, including the proton transfer process and global conformational motions. We found that high concentration crystallization solutions (NH4)2SO4 strongly inhibit the structural dynamics of PYP upon blue light excitation. We will examine and discuss the mechanism in which crystallization solutions inhibit protein structural dynamics. The results are expected to provide insights to fundamental understanding of protein crystallization of water-soluble proteins. In addition, the data clearly demonstrates that the structural dynamics observed in crystalline conditions may be far from their natural structural dynamics for studies of protein structure-function relations.

Thubagere, Anupama; Kelemen, Lorand; Kaledhonkar, Sandip; Xie, Aihua

2007-03-01

123

Crystal Structure of Chabazite K  

SciTech Connect

The crystal structure of the chabazite K with the formula (K{sub 1.33}Na{sub 1.02}Ca{sub 0.84})[Al{sub 4}Si{sub 8}O{sub 24}] {center_dot} 12.17H{sub 2}O from late hydrothermalites in the Khibiny alkaline massif (Kola Peninsula) is established by X-ray diffraction analysis (CAD4 four-circle diffractometer, {lambda}MoK{sub {alpha}} radiation, graphite monochromator, T = 193 K, 2{theta}{sub max} = 70 deg., R{sub 1} = 0.047 for 4745 reflections) on the basis of experimental data (6265 reflections) obtained from a twin (twinning parameter 0.535(1)): a = 13.831(3) A, c = 15.023(5) A, sp. gr. R3-barm, Z = 3, {rho}{sub calcd} = 2.016 g/cm{sup 3} . It is shown that cations occupy five independent positions in large cavities of the tetrahedral Al,Si,O anionic framework in potassium-rich chabazite. A comparative crystallochemical analysis of chabazites of different composition and origin is performed.

Yakubovich, O.V.; Gavrilenko, P.G.; Pekov, I.V. [Moscow State University, Vorob'evy gory, Moscow, 119992 (Russian Federation); Massa, W. [Philipps University, Marburg (Germany)

2005-07-15

124

Crystal structure of a perfect carbyne  

NASA Astrophysics Data System (ADS)

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, ? = ? = ? = 118.5, and space group P3 m1. The perfect carbyne single crystals have a stable structure at room temperature if the length of their constituent chains is larger than 500 nm.

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

2008-01-01

125

Crystal structure of a perfect carbyne  

SciTech Connect

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.

Belenkov, E. A., E-mail: belenkov@csu.ru; Mavrinsky, V. V. [Chelyabinsk State University (Russian Federation)

2008-01-15

126

Novel Liquid Crystal Grating with a Relief Structure by a Simple UV Irradiation Process  

Microsoft Academic Search

A novel method of fabricating a liquid crystal grating is proposed. The liquid crystal grating, which has a periodic groove structure, can be fabricated by a simple single-step process with UV irradiation through a grating photomask using a mixture of liquid crystal and prepolymer materials. Phase separation in the UV curing process leads to completely separated layers of liquid crystal

Wen-Tao He; Toshiaki Nose; Susumu Sato

1998-01-01

127

A promising nonlinear optical material in the Mid-IR region: new results on synthesis, crystal structure and properties of noncentrosymmetric ?-HgBrCl.  

PubMed

This paper reports, for the first time, the nonlinear optical property of ?-HgBrCl, which was synthesized by a reaction of Hg2Cl2 and Br2 in EtOH. This reaction also gave ?-HgBrCl. And the single crystal structures of both ?- and ?-HgBrCl are presented and compared. ?-HgBrCl shows phase-matchable powder second harmonic generation (SHG) effect of about 2 times that of KH2PO4 (KDP). Its absorption edge in UV-vis spectrum locates at 366 nm, implying a wide band gap and therefore higher laser damage threshold. It also exhibits a relatively wide transparent window (from 0.4 to 20 ?m) and relatively good thermal stability. PMID:23695292

Dang, Yangyang; Meng, Xianggao; Jiang, Kui; Zhong, Cheng; Chen, Xingguo; Qin, Jingui

2013-07-21

128

Intelligent materials and structures revisited  

NASA Astrophysics Data System (ADS)

Presented are new definitions and interpretations for smartness and intelligence associated with materials, structures, and material systems (MS & MS). These newly proposed definitions complement and augment the present notion of smart and/or intelligent materials, structures and material systems, as accepted by our scientific community. These new definitions numerically quantify the concepts of smartness and intelligence for materials, structures and material systems. In this context amino acid sequences and structures such as proteins are proposed to be the smartest material family and are given an MSQ of 1000. Correspondingly, ribonucleic acid sequences such as RNA and DNA macromolecular assemblies and structures are proposed to be the most intelligent material family and are given an MIQ of 1000. In the same category the proteins are given an MIQ of about 700. Ionic polymeric gels, shape memory alloys, electromagnetic (electrostrictive, piezoelectric, ferroelectric, ferromagnetic) materials, electrorheological fluids and magnetorheological fluids are then categorized under this hierarchy of smart/intelligent materials with MSQs and MIQs of smaller values. A similar classification is also applied to smart/intelligent structures with reference to simple cells such as bacteria and viruses such as T4 Bacteriophages. A number of examples are presented and the corresponding MSQs and MIQs are estimated to show that materials, structure and material systems can truly be numerically categorized in connection with their smartness and intelligence and thus be compared with biological and botanical structures and material systems.

Shahinpoor, Mohsen

1996-02-01

129

Defect structures in metallic photonic crystals  

SciTech Connect

We have investigated metallic photonic crystals built around a layer-by-layer geometry. Two different crystal structures (face-centered-tetragonal and tetragonal) were built and their properties were compared. We obtained rejection rates of 7{endash}8 dB per layer from both metallic crystals. Defect modes created by removing rods resulted in high peak transmission (80{percent}), and high quality factors (1740). Our measurements were in good agreement with theoretical simulations. {copyright} {ital 1996 American Institute of Physics.}

Oezbay, E.; Temelkuran, B. [Department of Physics, Bilkent University, Bilkent, Ankara 06533 (Turkey)] [Department of Physics, Bilkent University, Bilkent, Ankara 06533 (Turkey); Sigalas, M.; Tuttle, G.; Soukoulis, C.M.; Ho, K.M. [Ames Laboratory and Microelectronics Research Center, Iowa State University, Ames, Iowa 50011 (United States)] [Ames Laboratory and Microelectronics Research Center, Iowa State University, Ames, Iowa 50011 (United States)

1996-12-01

130

Synthesis, crystal structure and thermal properties of Ca6(C12H14O4)4(CO3)(OH)2(H2O)x--a 3D inorganic hybrid material.  

PubMed

The inorganic-organic compound Ca(6)(1,3-adamantanedicarboxylate)(4)(CO(3))(OH)(2)(H(2)O)(x) with 0 < x < 15.2 was synthesized by hydrothermal methods. The crystal structure was determined on the basis of high resolution synchrotron powder diffraction data and poly-crystal measurements. The crystal structure of Ca(6)(C(12)H(14)O(4))(4)(CO(3))(OH)(2)(H(2)O)(14) is tetragonal, space group I4(1)/amd (141) with a = 29.12 , c = 15.85 , V = 13,440 (3) and Z = 8. The compound is classified as a 3D inorganic hybrid material with a 3-dimensional inorganic framework consisting of Ca and O, connected to 1,3-adamantanedicarboxylate anions. The structure shows hydrophilic channels in a diamond-like network. In between the channels there exist hydrophobic pores with surfaces defined by adamantane cages. The shortest distance between hydrogen atoms from different molecules in these pores is 3.6 . The largest hydrophilic cavity has a diameter of 10 and the pores connecting the channels have a diameter of 5 . In the as-synthesised state these channels are filled with water molecules. Reversible dehydration-rehydration occurs. The dehydrated compound easily takes up water from ambient air. PMID:22914759

Nielsen, Renie Birkedal; Norby, Poul; Kongshaug, Kjell Ove; Fjellvg, Helmer

2012-10-21

131

Isotropic behavior of an anisotropic material: single crystal silicon  

NASA Astrophysics Data System (ADS)

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 components and will provide subsecond thermal equilibrium and sub-micron creep.

McCarter, Douglas R.; Paquin, Roger A.

2013-09-01

132

Introduction to Crystal Structure: Bond Strength  

NSDL National Science Digital Library

This exercise is designed to familiarize students with some basic crystal structures The exercise helps students fully understand the nature and significance of ionic bonds and Pauling's second rule It also builds a bit on Pauling's first rule (radius ratio principle) It is one of several related activities, all of which are intended to help students understand the nature of ionic crystals

Perkins, Dexter

133

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

NASA Astrophysics Data System (ADS)

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.

Sankari, R. Siva; Perumal, Rajesh Narayana

2014-04-01

134

Method of making macrocrystalline or single crystal semiconductor material  

NASA Technical Reports Server (NTRS)

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.

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

1986-01-01

135

Crystal structure of ScB/sub 12/  

SciTech Connect

The crystal structure of scandium dodecaboride was determined. The research material was a single crystal derived from an ingot obtained by fusion of metallic Sc and finely crystalline boron in an electric-arc furnace (Ar atmosphere). We used Laue, rotation, and inverse-lattice photography methods. The data confirmed that ScB/sub 12/ has a face-centered cubic structure. The investigation showed that with regard to the composition and structure of the resulting borides Sc exhibits complete analogy with Zr and is less similar to yttrium-group rare earth metals, for which the formation of tetraborides and hexaborides is characteristic.

Bruskov, V.A.; Zavalii, L.V.; Kuz'ma, Yu.B.

1988-08-01

136

Self-monitoring structural materials  

Microsoft Academic Search

Self-monitoring (or intrinsically smart) structural materials, including concrete containing short carbon fibers, and polymer-matrix and carbon-matrix composites containing continuous carbon fibers, were reviewed. Each material is capable of monitoring its own reversible strain and damage through the effects of these on the electrical resistance of the material. This capability is valuable for structural control and structural health monitoring. Among these

D. D. L. Chung

1998-01-01

137

ICSD Web: the Inorganic Crystal Structure Database  

NSDL National Science Digital Library

This site contains a free demonstration version of the Inorganic Crystal Structure Database. This database contains a 3325 structure subset of the 76,480 inorganic structures as of 2004. The demo version can be queried and accessed by a web-interface which allows multiple methods of searching, and the resulting crystal structures can then be viewed online (with the CHIME plug-in) or downloaded for viewing with other visualization software. Also included on the site are updates of bug fixes, conditions of use and prices, tips for displaying the structures, a gallery of images, a flash movie, and instructions for installing a ICSD server.

Alan, Hewat

138

FBR Structural Material Test Program.  

National Technical Information Service (NTIS)

In parallel with development of FBR, Power Reactor and Nuclear Fuel Development Corporation (PNC) has planned and carried out a series of structural material tests in order to establish the rational temperature designs for structural components. These mat...

1977-01-01

139

Composite structural materials  

NASA Technical Reports Server (NTRS)

Technology utilization of fiber reinforced composite materials is discussed in the areas of physical properties, and life prediction. Programs related to the Composite Aircraft Program are described in detail.

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

1979-01-01

140

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

DOEpatents

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.

Rollins, Harry W. (Idaho Falls, ID); Petkovic, Lucia M. (Idaho Falls, ID); Ginosar, Daniel M. (Idaho Falls, ID)

2011-02-01

141

Salt transport and crystallization in non-isothermal, partially saturated porous materials considering ions interaction model  

Microsoft Academic Search

Crystallizing salt changes the inner pore structure of materials. MIP tests of cement mortar and brick saturated with NaCl, Ca2Cl, Na2SO4 solutions were performed. The changes of porosity, pore size distribution and pore shape (ink-bottle type pores) were investigated by performing two intrusionextrusion cycles. The crystallization pressure bursts the mezopores. During salt crystallization the additional heat is released, which must

Marcin Koniorczyk

142

Structures of cyano-biphenyl liquid crystals  

NASA Technical Reports Server (NTRS)

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.

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

1989-01-01

143

Liquid Crystals and Spatial Light Modulator Materials,  

National Technical Information Service (NTIS)

Ferroelectric liquid crystal (FLC) compounds are investigated for use in optical parallel processing. Spatial light modulators using the smectic C phase FLC's show better contrast ratio, faster switching speeds, and lower cost than twisted nematic liquid ...

L. A. Pagano-Stauffer K. M. Johnson N. Clark M. Handschy

1986-01-01

144

Liquid Crystal Materials for Laser Beam Steering.  

National Technical Information Service (NTIS)

Several new liquid crystal compounds have been developed for laser beam steering application. The asymmetric diakyl diphenyl-diacetylenes exhibit a low melting temperature, wide nematic range, high birefringence, low viscosity and small heat fusion enthal...

J. D. Margerum S. T. Wu

1994-01-01

145

Optical and physical properties of ceramic crystal laser materials  

NASA Astrophysics Data System (ADS)

Historically ceramic crystal laser material has had disadvantages compared to single crystal laser material. However, progress has been made in the last decade and a half to overcome the disadvantages associated with ceramic crystal. Today, because of the promise of ceramic crystal as a high power laser material, investigation into its properties, both physical and optical, is warranted and important. Thermal expansion was measured in this thesis for Nd:YAG (yttrium aluminum garnet) ceramic crystal using an interferometric method. The interferometer employed a spatially filtered HeNe at 633 nm wavelength. Thermal expansion coefficients measured for the ceramic crystal samples were near the reported values for single crystal Nd:YAG. With a similar experimental setup as that for the thermal expansion measurements, dn/dT for ceramic crystal Nd:YAG was measured and found to be slightly higher than the reported value for single crystal. Depolarization loss due to thermal gradient induced stresses can limit laser performance. As a result this phenomenon was modeled for ceramic crystal materials and compared to single crystals for slab and rod shaped gain media. This was accomplished using COMSOL Multiphysics, and MATLAB. Results indicate a dependence of the depolarization loss on the grain size where the loss decreases with decreased grain size even to the point where lower loss may be expected in ceramic crystals than in single crystal samples when the grain sizes in the ceramic crystal are sufficiently small. Deformation-induced thermal lensing was modeled for a single crystal slab and its relevance to ceramic crystal is discussed. Data indicates the most notable cause of deformation-induced thermal lensing is a consequence of the deformation of the top and bottom surfaces. Also, the strength of the lensing along the thickness is greater than the width and greater than that due to other causes of lensing along the thickness of the slab. Emission spectra, absorption spectra, and fluorescence lifetime were measured for Nd:YAG ceramic crystal and Yb:Lu2O3 ceramic crystal. No apparent inhomogeneous broadening appears to exist in the Nd:YAG ceramic at low concentrations. Concentration and temperature dependence effects on emission spectra were measured and are presented. Laser action in a thin disk of Yb:Y2O3 ceramic crystal was achieved. Pumping was accomplished with a fiber coupled diode laser stack at 938 nm. A slope efficiency of 34% was achieved with maximum output energy of 28.8 mJ/pulse.

Simmons, Jed A.

146

Crystal engineering: From design of crystal structures to fabrication of composite crystals  

NASA Astrophysics Data System (ADS)

This thesis reports how to design and control co-crystal structures from a kinetic point of view, and demonstrates the control of crystal morphology through understanding the kinetics and crystal structures. In chapter one, the in-situ atomic force microscope (AFM) was utilized to investigate how side chain on a glycine 2,5-diketopiperazine (GLYDKP) backbone can affect the assembly of GLYDKP, and showed that methyl groups cause larger energy barrier for crystallization. Because the introduction of functional group on the side chain could inevitably slow down the assembly process, a different approach should be considered. Chapter two shows that formic acid at low concentration can accelerate the assembly process without incorporating into the crystal structure. Because formic acid only crystallizes with GLYDKP in concentrated solution, these results prove that co-crystallization is a better method for incorporating functionalized molecules into a solid than direct modification of molecule itself. Chapter three focuses on the rational design of GLYDKP cocrystals by utilizing the observation found in chapter two. Structure of GLYDKP and formic acid crystal was analyzed to search possible guest molecules for cocrystal studies. This method successfully identified eleven molecules that crystallize with GLYDKP, and proved that crystal structure can be controlled through weak interactions such as C-HO=C and C-HCl interactions. Chapter four and chapter five explore the possibility of using self-assembled process to control morphology of crystals and surface epitaxy. Metal(II) bis(imidazolium 2,b-pyridinedicarboxylate) complexes were chosen and two morphologies associated with different metal ions were found: rhombohedral (Type I) and rectangular (Type II) crystals. In this study, an additive was found to change the morphology of crystal from type I to type II, and then methods of producing various shapes of composite crystals were also established. These self-assembled procedures of making composite crystals at micron scale are very promising, because the fabrication will only relies on solvent, additives, or combination of them without using sophisticated crystallizers.

Luo, Tzy-Jiun Mark

147

Synthesis, X-ray crystal structures, and gas sorption properties of pillared square grid nets based on paddle-wheel motifs: implications for hydrogen storage in porous materials.  

PubMed

A systematic modulation of organic ligands connecting dinuclear paddle-wheel motifs leads to a series of isomorphous metal-organic porous materials that have a three-dimensional connectivity and interconnected pores. Aromatic dicarboxylates such as 1,4-benzenedicarboxylate (1,4-bdc), tetramethylterephthalate (tmbdc), 1,4-naphthalenedicarboxylate (1,4-ndc), tetrafluoroterephthalate (tfbdc), or 2,6-naphthalenedicarboxylate (2,6-ndc) are linear linkers that form two-dimensional layers, and diamine ligands, 4-diazabicyclo[2.2.2]octane (dabco) or 4,4'-dipyridyl (bpy), coordinate at both sides of Zn(2) paddle-wheel units to bridge the layers vertically. The resulting open frameworks [Zn(2)(1,4-bdc)(2)(dabco)] (1), [Zn(2)(1,4-bdc)(tmbdc)(dabco)] (2), [Zn(2)(tmbdc)(2)(dabco)] (3), [Zn(2)(1,4-ndc)(2)(dabco)] (4), [Zn(2)(tfbdc)(2)(dabco)] (5), and [Zn(2)(tmbdc)(2)(bpy)] (8) possess varying size of pores and free apertures originating from the side groups of the 1,4-bdc derivatives. [Zn(2)(1,4-bdc)(2)(bpy)] (6) and [Zn(2)(2,6-ndc)(2)(bpy)] (7) have two- and threefold interpenetrating structures, respectively. The non-interpenetrating frameworks (1-5 and 8) possess surface areas in the range of 1450-2090 m(2)g(-1) and hydrogen sorption capacities of 1.7-2.1 wt % at 78 K and 1 atm. A detailed analysis of the sorption data in conjunction with structural similarities and differences concludes that porous materials with straight channels and large openings do not perform better than those with wavy channels and small openings in terms of hydrogen storage through physisorption. PMID:15761853

Chun, Hyungphil; Dybtsev, Danil N; Kim, Hyunuk; Kim, Kimoon

2005-06-01

148

Thermoelectric Materials With the Skutterudite Structure: New Results  

NASA Technical Reports Server (NTRS)

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.

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

1995-01-01

149

Structural properties of a C120 crystal  

NASA Astrophysics Data System (ADS)

With well-know models used for the study of orientational ordering transition in C60 crystal and with the crystallographic data from G-W. Wang and al.[Nature 387,583(1997)], this work aimed at characterizing a possible orientational ordering transition in C120 crystal. The C120 molecular structure used is based on MNDO optimization. With the same model, we have investigated the effect of the crystal surface on the ordering phase temperature. An orientational ordering phase transition was predicted to take place at 220K in the bulk and 175K at the surface.

Laforge, Christophe; Senet, Patrick; Lambin, Philippe

1998-08-01

150

Composite structural materials  

NASA Technical Reports Server (NTRS)

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.

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

1983-01-01

151

Microscopic characterization of defect structure in RDX crystals.  

PubMed

Three batches of the commercial energetic material RDX, as received from various production locations and differing in sensitivity towards shock initiation, have been characterized with different microscopic techniques in order to visualize the defect content in these crystals. The RDX crystals are embedded in an epoxy matrix and cross-sectioned. By a treatment of grinding and polishing of the crystals, the internal defect structure of a multitude of energetic crystals can be visualized using optical microscopy, scanning electron microscopy and confocal scanning laser microscopy. Earlier optical micrographs of the same crystals immersed in a refractive index matched liquid could visualize internal defects, only not in the required detail. The combination of different microscopic techniques allows for a better characterization of the internal defects, down to inclusions of approximately 0.5 ?m in size. The defect structure can be correlated to the sensitivity towards a high-amplitude shock wave of the RDX crystals embedded in a polymer bonded explosive. The obtained experimental results comprise details on the size, type and quantity of the defects. These details should provide modellers with relevant and realistic information for modelling defects in energetic materials and their effect on the initiation and propagation of shock waves in PBX formulations. PMID:24117989

Bouma, R H B; Duvalois, W; Van der Heijden, A E D M

2013-12-01

152

Design considerations for a Space Shuttle Main Engine turbine blade made of single crystal material  

NASA Technical Reports Server (NTRS)

Nonlinear finite-element structural analyses were performed on the first stage high-pressure fuel turbopump blade of the Space Shuttle Main Engine. The analyses examined the structural response and the dynamic characteristics at typical operating conditions. Single crystal material PWA-1480 was considered for the analyses. Structural response and the blade natural frequencies with respect to the crystal orientation were investigated. The analyses were conducted based on typical test stand engine cycle. Influence of combined thermal, aerodynamic, and centrifugal loadings was considered. Results obtained showed that the single crystal secondary orientation effects on the maximum principal stresses are not highly significant.

Abdul-Aziz, A.; August, R.; Nagpal, V.

1993-01-01

153

Optics of magnetic photonic crystals with mu-negative materials  

NASA Astrophysics Data System (ADS)

In this paper, we have made an analysis of the optics of magnetic photonic crystals having mu-negative materials. We consider the magnetic photonic crystal with different values of the magnetic permeability of the materials (PIM). Such materials will be affected by the applied magnetic field and can also exhibit the properties of superconducting materials. We infer that PhC with MNM and PIM materials can be used as tunable devices by choosing proper thickness, damping factor, and mu-value of the PIM.

Kumar, N.; Thapa, K. B.; Janma, Ram; Pandey, G. N.; Reena

2013-06-01

154

Crystal growth, thermal and optical studies of semiorganic nonlinear optical material: L-lysine hydrochloride dihydrate  

SciTech Connect

Single crystals of L-lysine hydrochloride dihydrate (LLHCD), a nonlinear optical material, have been grown by slow cooling technique from its aqueous solution. LLHCD was found to be highly soluble in water. The grown crystals have been subjected to single crystal X-ray diffraction to confirm the structure and to estimate the lattice parameters. The vibrational structure of the molecule is elucidated from FTIR spectra. Thermal analysis revealed the thermal stability of the grown crystals. The optical transmittance spectrum shows that the material possesses good optical transparency in the entire visible region with a UV cut-off wavelength at 228 nm. The mechanical properties of the grown crystal have been studied using Vicker's microhardness test. The laser damage threshold of 52.25 MW/cm{sup 2} has been measured by irradiating Q-switched Nd:YAG laser (1064 nm)

Kalaiselvi, D.; Mohan Kumar, R. [Crystal Growth Centre, Anna University, Chennai 600025 (India); Jayavel, R. [Crystal Growth Centre, Anna University, Chennai 600025 (India)], E-mail: rjvel@yahoo.com

2008-07-01

155

Electrooptical Switching of Ferroelectric Liquid Crystals in Electrically Distorted Chevron Structure  

Microsoft Academic Search

X-ray diffraction studies on the field induced distortion of the layer structure in ferroelectric liquid crystals are reported. Depending on the liquid crystal materials and alignment layers, electric fields produced reversible or irreversible distortions. Bistable electrooptical switching was observed only in the samples with the irreversibly distorted layer structure. Experimental results on the light transmissions indicated that a bookshelf-like structure

M. Isogai; M. Oh-e; T. Kitamura; A. Mukoh

1991-01-01

156

Preparation Techniques for Growth of Single Crystals of Nonmetallic Materials.  

National Technical Information Service (NTIS)

The report describes two techniques for growth of highpurity single crystals of nonmetallic materials using r-f induction-heating equipment in a frequency range of 5 to 100 Mc. One technique used for single-crystal growth was the Verneuil method using an ...

E. M. Clausen J. W. Rutter

1964-01-01

157

Doping and Defect Structure of Tetradymite-Type Crystals  

NASA Astrophysics Data System (ADS)

Nonstoichiometry of tetradymite-type crystals A{2/V}B{3/VI} that are grown from stoichiometric melts leads to the formation of native defects in the crystal lattice (predominantly antisite defects, A{B/-1} and vacancies V{B/+2} in the anion sublattice). This paper summarizes the basic ideas concerning a point defect model in A{2/V}B{3/VI} crystals. It turns out that a variety of doping elements interact with the native defects. Such interactions alter the concentration of free charge carriers, affect the doping efficiency, and modify the transport properties. Detailed understanding of the defect structure in tetradymite-type crystals is very important as it impacts on the efficiency of these materials when used as active elements in thermoelectric coolers.

Drasar, C.; Lostak, P.; Uher, C.

2010-09-01

158

Solvothermal synthesis, crystal structure, and second-order nonlinear optical properties of a new noncentrosymmetric gallium-organic framework material, [N(C3H7)4]3Ga3[C6H3(CO2)3]4  

NASA Astrophysics Data System (ADS)

A novel noncentrosymmetric (NCS) gallium-organic framework material, [N(C3H7)4]3Ga3[C6H3(CO2)3]4 (CAUMOF-11) has been synthesized by a solvothermal reaction using Ga(NO3)3xH2O, 1,3,5-C6H3(CO2H)3, N(C3H7)4Cl, HNO3, and HCON(CH3)2 at 180 C. The structure of the reported material has been determined by single-crystal X-ray diffraction. CAUMOF-11 has an anionic three-dimensional framework with aligned four-coordinate GaO4 tetrahedra and 1,3,5-benzenetricarboxylate groups. Tetrapropylammonim cations reside within the channel and maintain the charge balance. Detailed structural analyses with full characterization including infrared spectroscopy, thermogravimetric analysis, elemental analysis, ion-exchange reactions, topotactic decomposition, and gas adsorption experiments are reported. Powder second-harmonic generating (SHG) measurements on CAUMOF-11, using 1064 nm radiation, exhibit SHG efficiency of 15 times that of ?-SiO2 and the material is phase-matchable (type-1).

Lee, Dong Woo; Jo, Vinna; Ok, Kang Min

2012-10-01

159

Synthesis and crystal structure of maleopimaric acid.  

PubMed

The title compound maleopimaric acid was synthesized by a Diels-Alder reaction between maleic anhydride and Pinus elliottii engelm oleoresin at room temperature and it was characterized by single crystal X-ray diffraction. The white crystals crystallized in the orthorhombic system, space group P2(12121) with cell dimensions: a = 7.6960 (15) A, b = 11.851 (2) A, c = 24.577 (5) A, alpha = 90 degrees, beta = 90 degrees, gamma = 90 degrees, V = 2241.6(8) A(3), and R(1) = 0.0716, wR(2) = 0.1975. The two fused and unbridged cyclohexane rings form a trans ring junction with chair conformation with two methyl groups in axis positions, the anhydride ring is planar. Crystal water existed in the molecular and stabilized the structure through intermolecular hydrogen bonds. PMID:18626819

Rao, Xiaoping; Song, Zhanqian; Yao, Xujie; Han, Chunrui; Shang, Shibin

2008-01-01

160

Confined Crystals of the Smallest Phase-Change Material  

PubMed Central

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.

2013-01-01

161

Building Crystal Structure Ball Models Using Pre-Drilled Templates: Sheet Structures, Tridymite, and Cristobalite  

NSDL National Science Digital Library

This activity involves building crystal structure ball models in order to strengthen students' understanding of crystalline order, relative atomic size, atomic coordination, crystal chemistry, and crystal symmetry.

Hollocher, Kurt

162

New Energetic Materials - Structural Characterization.  

National Technical Information Service (NTIS)

The molecular structures of five new materials developed in ONR-sponsored explosive/propellant research are reported. The material 3,3-bis-azidomethyl oxetane (BAMO) was studied in three different forms. Using gas electron diffraction analysis, the molecu...

R. Gilardi C. F. George J. Karle

1981-01-01

163

Application of Relaxation Methods in Materials Science: From the Macroscopic Response of Elastomers to Crystal Plasticity  

Microsoft Academic Search

\\u000a In this contribution we review some aspects of the mathematical analysis of fine structures in materials in three distinct\\u000a systems: small deformations within the range of pseudoelasticity in shape memory materials, soft elasticity for nematic and\\u000a smectic elastomers, and relaxation via formation of microstructures in single crystal plasticity.

Georg Dolzmann

164

Structural and optical properties of a new chalcone single crystal  

NASA Astrophysics Data System (ADS)

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 2622 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) , b=15.3022(6) , c=16.0385(7) , ?=?=?=90, volume=1463.37(10) 3 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.

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

2012-09-01

165

Crystal structure of Arabidopsis thaliana cytokinin dehydrogenase  

SciTech Connect

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).

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

2008-08-13

166

Crystal structure and density of helium to 232 kbar  

NASA Technical Reports Server (NTRS)

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.

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

1988-01-01

167

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

NASA Astrophysics Data System (ADS)

We for the first time applied x-ray diffraction microscopy to the imaging of mineral crystals inside biological composite materialsintramuscular fish boneat 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.

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

2008-01-01

168

High-pressure structural studies of energetic materials  

Microsoft Academic Search

This article reviews how the advances in the techniques for the collection and analysis of high-pressure X-ray and neutron diffraction data, augmented by spectroscopic data, now permit the accurate determination of the full crystal structure of energetic materials under extreme conditions. Using these methods, the crystal structure of the high-pressure ?-form of RDX (1,3,5-trinitrohexahydro-s-triazine) has been determinedthe first case of

David I. A. Millar; William G. Marshall; Iain D. H. Oswald; Colin R. Pulham

2010-01-01

169

Novel polymer as liquid crystal alignment material for plastic substrates  

NASA Astrophysics Data System (ADS)

Implementation of the roll-to-roll (R2R) process and printable organic electronics realizes the cost reduction potential of liquid crystal displays (LCDs) on plastic substrates. These innovative technologies put a strong limitation on the chemistry and temperature treatment of the LC alignment material applied at the solid-liquid interface inside the LCD. Alignment material is the last uniform layer deposited on each of the substrates before assembling and sealing of the whole display sandwich. Deposition from an aggressive solvent, vacuum deposition or a high baking temperature can not only destroy the complex composite structure of the electronics but can also affect the material properties of the substrate. We developed a new type of polymer alignment material, B-15, which can be deposited from a non-aggressive solvent (ethyl/butyl acetate) on top of the wide range of organic layers (including UV-curable materials and TAC films of plastic polarizer) without barrier layers for chemical protection. B-15 is suitable for the R2R process for only short-time treatment operations: 5 min baking at 90 C is sufficient to remove the residual solvent and hard baking is not required. First, the rubbing process produces an alignment direction on the surface with the azimuthal anchoring energy over 10-4 J m-2. Next, non-polarized light exposure with a 254 nm Hg line induces photopolymerization, which also shifts the absorption peak far below the 300 nm wavelength. Thus B-15 is a highly photostable alignment material possessing null absorption in both the UV-A and the VIS ranges.

Mahilny, U. V.; Stankevich, A. I.; Muravsky, A. A.; Murauski, A. A.

2009-04-01

170

Nanowire-Photonic Crystal Waveguide Hybrid Structure  

Microsoft Academic Search

We propose a class of nanocavities by combining nanowires and photonic crystal waveguides. Three-dimensional finite-difference time-domain techniques have been used to study the structures, and the simulation results show it is easy to achieve nanocavities with mode volumes less than 2(lambda\\/n)3 and Q values over 106 .

Chu-Cai Guo; Myung-Ki Kim; Se-Heon Kim; Yong-Hee Lee

2007-01-01

171

Crystal structure of a plectonemic RNA supercoil  

SciTech Connect

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.

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

2012-12-14

172

Structure analysis on synthetic emerald crystals  

NASA Astrophysics Data System (ADS)

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.

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

2013-05-01

173

Critical parameters of superconducting materials and structures  

SciTech Connect

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.

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

1995-02-01

174

Crystal Structure of Human Enterovirus 71  

SciTech Connect

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.

Plevka, Pavel; Perera, Rushika; Cardosa, Jane; Kuhn, Richard J.; Rossmann, Michael G. (Purdue); (Sentinext)

2013-04-08

175

The crystal structures of DNA Holliday junctions  

Microsoft Academic Search

Nearly 40 years ago, Holliday proposed a four-stranded complex or junction as the central intermediate in the general mechanism of genetic recombination. During the past two years, six single-crystal structures of such DNA junctions have been determined by three different research groups. These structures all essentially adopt the antiparallel stacked-X conformation, but can be classified into three distinct categories: RNADNA

P. Shing Ho; Brandt F Eichman

2001-01-01

176

Crystal and electronic structure of copper sulfides  

Microsoft Academic Search

Copper sulfides with different copper concentration exist in mineral form ranging from CuS to Cu2S. Among these, chalcosite Cu 2S, and digenite Cu1.8S were the subject of extensive research for decades mainly because of their use as the absorber in photovoltaic cells. Yet; their electronic structure is poorly understood because their crystal structure is complex. Most of the results published

Pavel Lukashev

2007-01-01

177

Crystal structure of a nonsymbiotic plant hemoglobin  

Microsoft Academic Search

Background: Nonsymbiotic hemoglobins (nsHbs) form a new class of plant proteins that is distinct genetically and structurally from leghemoglobins. They are found ubiquitously in plants and are expressed in low concentrations in a variety of tissues including roots and leaves. Their function involves a biochemical response to growth under limited O2 conditions.Results: The first X-ray crystal structure of a member

Mark S Hargrove; Eric Allen Brucker; Boguslaw Stec; Gautam Sarath; Ral Arredondo-Peter; Robert V Klucas; John S Olson; George N Phillips

2000-01-01

178

Structural characterisation of advanced optical materials  

NASA Astrophysics Data System (ADS)

The rare earth systems discussed in this thesis belong to a class of new, advanced optical materials. Two different nanostuctured materials are studied: nanocrystalline oxide phosphors and glass ceramics containing luminescent nanocrystals. In both cases, the optical activity is based on the luminescence properties of rare earth dopants incorporated into the crystal structure of the insulator nanocrystals themselves. The structure, morphology and composition of these luminescent composite materials are investigated and used to demonstrate the benefits as well as the drawbacks of the synthesis and the processing techniques used, aiming to their improvement for possible industrial production. An investigation of the microstructure was done by XRD, TEM and HREM, while EDX, EELS and EFTEM spectroscopy techniques were used for the chemical identification. Our research clearly demonstrated that these techniques can be successfully applied, and in combination with optical spectroscopy can provide the complete characterization of nanostructured luminescent materials. Three different oxide phosphors in the form of nanocrystalline powders are obtained with the solution combustion technique: yttrium aluminum garnet (YAG), gadolinium gallium garnet (GGG) and scandium oxide, Sc2O 3. We found out that GGG and Sc2O3 samples have "perfect" nanocrystals, without defects or amorphous surface layer, and with uniform distribution of rare earth activators. Good crystal quality results in a long-lived phosphor and much stronger emission, which makes them promising candidate for display industry. Moreover, these luminescent nanocrystals are biocompatible and when functionalized with some molecules or biocompatible polymers can be used for bio-applications like "in vivo" markers in cell biology. For luminescence glass ceramics samples the ternary glass system Li 2O-Al2O3-SiO2 (LAS) is used as host matrix, and ZrO2 as nucleating agent for luminescent ions introduced as Eu2O3 or Er2O3. We wanted to obtain a composite with crystal-like optical properties, keeping the transparency and the processibility of the glass host. The spatial distribution of the precipitates throughout the material, their morphology, structure and composition are investigated with various TEM modes to check if we succeed in draining all rare earth dopant ions from the matrix into ZrO2 crystals. The best results are obtained for the samples containing Er as dopant.

Krsmanovic, Radenka

179

Materials for Freeform Fabrication of GHz Tunable Dielectric Photonic Crystals.  

National Technical Information Service (NTIS)

Photonic crystals are of interest for GHz transmission applications, including rapid switching, GHz filters, and phased-array technology. 3D fabrication by Robocasting enables moldless printing of high solid loading slurries into structures such as the 'w...

J. Cesarano J. E. Smay J. F. Carroll M. K. Niehaus P. G. Clem

2003-01-01

180

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

PubMed

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

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

2014-01-24

181

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

PubMed

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)(?), b=17.1392(12)(?), c=17.1392(12)(?), ?=117.339(0), ?=99.487(0), ?=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

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

2014-12-10

182

First-principles materials applications and design of nonlinear optical crystals  

NASA Astrophysics Data System (ADS)

With the development of laser technology and related scientific fields, understanding of the structureproperty relationships in nonlinear optical (NLO) crystals is becoming more and more important. In this article, first-principles studies based on density functional theory, and their applications to elucidate the microscopic origins of the linear and NLO properties in NLO crystals, are reviewed. The ab initio approaches have the ability to accurately predict the optical properties in NLO crystals, and the developed analysis tools are vital to investigating their intrinsic mechanism. This microscopic understanding has further guided molecular engineering design for NLO crystals with novel structures and properties. It is anticipated that first-principle material approaches will greatly improve the search efficiency and greatly help experiments to save resources in the exploration of new NLO crystals with good performance.

Lin, Zheshuai; Jiang, Xingxing; Kang, Lei; Gong, Pifu; Luo, Siyang; Lee, Ming-Hsien

2014-06-01

183

Evolution of crystal structures in metallic elements  

NASA Astrophysics Data System (ADS)

Crystal structures of metals are often treated as dense packing of atomic spheres. Face-centered cubic and hexagonal close-packed structures are favored in many metals. Long-period-stacking structures such as 9R are sometimes formed. However, nonclose packed structures such as body centered cubic and ? are formed depending upon chemistry and process conditions. Even in metallic elements, it is a priori unknown how such close/nonclose packed structures are formed and what are their interrelationships. In the present study we show a simple algorithm for automated searching of the phase-transition pathway based upon first-principles calculations, which is applied to systematically pursue the evolution of crystal structures. Following the present algorithm, dynamical stability and interrelationships of different structures generated from a simple cubic structure are revealed for seven metallic elements. Effects of pressure are examined as well. The powerfulness of the automated method to investigate the nature of the phase transition and to predict as-yet-unknown metastable structures is demonstrated.

Togo, Atsushi; Tanaka, Isao

2013-05-01

184

Crystal structure of columbite under high pressure  

NASA Astrophysics Data System (ADS)

The structural evolution of two columbites under pressure, one ferrocolumbite from Raode (Africa) and one manganocolumbite from Kragero (Norway), has been determined by single-crystal X-ray diffraction. Structural investigations at high pressure have been carried out on samples which were preliminarily annealed to attain the complete cation-ordered state. For each crystal, five complete datasets have been collected from room pressure up to ca. 7 GPa. Structure refinements converged to final discrepancy factors R ranging between 5.2 and 5.8% for both the crystals. Structure refinements of X-ray diffraction data at different pressures allowed characterisation of the mechanisms by which the columbite structure accommodates variations in pressure. A and B octahedral volumes in both samples decrease linearly as pressure increases, with a larger compression of the larger A site. The difference in polyhedral bulk moduli of the A sites for the two samples does not appear to relate directly to the octahedral sizes, the A site being more compressible in the Fe-rich sample than in the Mn-rich one. By far the most compressible direction in both the analysed samples is along b. The cations are in fact free to move along this direction, thus allowing the octahedral chains to slide over each other; this effect is particularly evident in the manganocolumbite sample which shows a steep shortening of interchain A-B distances along b.

Tarantino, Serena C.; Zema, Michele; Boffa Ballaran, Tiziana

2010-12-01

185

Crystal structure of low-symmetry rondorfite  

SciTech Connect

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.

Rastsvetaeva, R. K. [Russian Academy of Sciences, Shubnikov Institute of Crystallography (Russian Federation)], E-mail: rast@ns.crys.ras.ru; Zadov, A. E. [NPO Neokhim (Russian Federation); Chukanov, N. V. [Russian Academy of Sciences, Institute of Problems of Chemical Physics (Russian Federation)

2008-03-15

186

Crystal structure of low-symmetry rondorfite  

SciTech Connect

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.

Rastsvetaeva, R. K., E-mail: rast@ns.crys.ras.ru [Russian Academy of Sciences, Shubnikov Institute of Crystallography (Russian Federation); Zadov, A. E. [NPO Neokhim (Russian Federation); Chukanov, N. V. [Russian Academy of Sciences, Institute of Problems of Chemical Physics (Russian Federation)

2008-03-15

187

Crystal Structure of Toxoplasma gondii Porphobilinogen Synthase  

PubMed Central

Porphobilinogen synthase (PBGS) is essential for heme biosynthesis, but the enzyme of the protozoan parasite Toxoplasma gondii (TgPBGS) differs from that of its human host in several important respects, including subcellular localization, metal ion dependence, and quaternary structural dynamics. We have solved the crystal structure of TgPBGS, which contains an octamer in the crystallographic asymmetric unit. Crystallized in the presence of substrate, each active site contains one molecule of the product porphobilinogen. Unlike prior structures containing a substrate-derived heterocycle directly bound to an active site zinc ion, the product-bound TgPBGS active site contains neither zinc nor magnesium, placing in question the common notion that all PBGS enzymes require an active site metal ion. Unlike human PBGS, the TgPBGS octamer contains magnesium ions at the intersections between pro-octamer dimers, which are presumed to function in allosteric regulation. TgPBGS includes N- and C-terminal regions that differ considerably from previously solved crystal structures. In particular, the C-terminal extension found in all apicomplexan PBGS enzymes forms an intersubunit ?-sheet, stabilizing a pro-octamer dimer and preventing formation of hexamers that can form in human PBGS. The TgPBGS structure suggests strategies for the development of parasite-selective PBGS inhibitors.

Jaffe, Eileen K.; Shanmugam, Dhanasekaran; Gardberg, Anna; Dieterich, Shellie; Sankaran, Banumathi; Stewart, Lance J.; Myler, Peter J.; Roos, David S.

2011-01-01

188

Crystal structure of riboflavin synthase  

SciTech Connect

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.

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

2010-03-05

189

The crystal structure of SmPtSi  

Microsoft Academic Search

The ternary compound SmPtSi was found in studying the phase diagram of Sm-Pt-Si system (870 K). This work is concerned with the determination of the SmPtSi crystal structure. The X-ray diffraction study (using an RKD-57.3 camera and CrK radiation) of alloys obtained by fusion of the starting materials (Sm content is 0.9998, Pt and Si contents are 0.9999 mass fractions)

Zh. M. Barakatova; Yu. D. Seropegin; O. I. Bodak

1995-01-01

190

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

NASA Astrophysics Data System (ADS)

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.

Thirumurugan, R.; Anitha, K.

2014-04-01

191

Comment on the paper "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" by P.M. Dinakaran, S. Kalainathan [Spectrochim. Acta A 111 (2013) 123-130].  

PubMed

We argue that (trans)-4-chloro-4'-nitrostilbene is not a new organic nonlinear optical material as claimed by Dinakaran and Kalainathan [P.M. Dinakaran, S. Kalainathan, 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, Spectrochim. Acta A 111 (2013) 123-130], but instead a well-known compound whose synthesis, spectral data, single crystal structure and second harmonic generation (SHG) efficiency are well documented in the literature. The title paper is completely erroneous. PMID:24152596

Srinivasan, Bikshandarkoil R; Dhuri, Sunder N; Nadkarni, V S

2014-01-01

192

The crystal structures of DNA Holliday junctions.  

PubMed

Nearly 40 years ago, Holliday proposed a four-stranded complex or junction as the central intermediate in the general mechanism of genetic recombination. During the past two years, six single-crystal structures of such DNA junctions have been determined by three different research groups. These structures all essentially adopt the antiparallel stacked-X conformation, but can be classified into three distinct categories: RNA-DNA junctions; ACC trinucleotide junctions; and drug-induced junctions. Together, these structures provide insight into how local and distant interactions help to define the detailed and general physical features of Holliday junctions at the atomic level. PMID:11406378

Ho, P S; Eichman, B F

2001-06-01

193

Liquid crystal photoalignment material based on chloromethylated polyimide  

SciTech Connect

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.

Zhong Zhenxin; Li Xiangdan; Lee, Seung Hee; Lee, Myong-Hoon [Department of Polymer Science and Technology, Chonbuk National University, 664-I Dukjin, Chonju, Chonbuk 561-756 (Korea, Republic of)

2004-09-27

194

"SiAION" Materials for Advanced Structural Applications  

NASA Technical Reports Server (NTRS)

New ceramics for gas turbines and other applications are strong, oxidation resistant, and chemically stable. Recently prepared state-of-the-art report on SiAION materials includes work on phase relations, crystal structure, synthesis, fabrication, micro-structure, and properties of various SiAION's.

Dutta, S.

1982-01-01

195

Crystal structure of ultrathin lamellar precipitates  

NASA Astrophysics Data System (ADS)

The crystal structure of lamellar precipitates formed in alloys 1213 (Al-Cu-Ag), V-1461 (Al-Cu-Li) and V-1469 (Al-Cu-Li-Ag) has been studied during age hardening. The experimental studies have been performed using transmission electron microscopy. The precipitates have {111} habits and thicknesses of several atomic planes. In diffraction patterns, these plates give a system of diffuse streaks. These ultrathin plates scatter electrons similar to two-dimensional crystal lattices. It is shown that thin plates of precipitates in alloys 1213, V-1461, and V-1469 give identical systems of diffuse streaks. The two-dimensional crystal lattices that give the system of these streaks have a hexagonal symmetry with the following orientation relationship: {ie481-1} and the lattice parameter a f = 0.495 nm (there is no lattice parameter c f for two-dimensional lattices). A sequence of the steps of reconstruction of the spatial structure of plane precipitates is proposed in terms of their thickness, structures of two-dimensional lattices, and type of precipitates (extrinsic or intrinsic). The influence of Ag on the structure of lamellar precipitates in the V-1469 alloy is discussed.

Alekseev, A. A.; Lukina, E. A.; Klochkova, Yu. Yu.

2013-06-01

196

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

NASA Astrophysics Data System (ADS)

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.

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

2004-03-01

197

Use of Pom Pons To Illustrate Cubic Crystal Structures  

NASA Astrophysics Data System (ADS)

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.

Cady, Susan G.

1997-07-01

198

Crystal structure of ammonia monohydrate phase II.  

PubMed

We have determined the crystal structure of ammonia monohydrate phase II (AMH II) employing a combination of ab initio computational structure prediction and structure solution from neutron powder diffraction data using direct space methods. Neutron powder diffraction data were collected from perdeuterated AMH II using the D2B high-resolution diffractometer at the Institut Laue-Langevin. AMH II crystallizes in space-group Pbca with 16 formula units in a unit-cell of dimensions a = 18.8285(4) A, b = 6.9415(2) A, c = 6.8449(2) A, and V = 894.61(3) A3 [rho(calc)(deuterated) = 1187.56(4) kg m(-3)] at 502 MPa, 180 K. The structure is characterized by sheets of tessellated pentagons formed by orientationally ordered O-D...O, O-D...N, and N-D...O hydrogen-bonds; these sheets are stacked along the a-axis and connected by N-D...O hydrogen bonds alone. With the exception of the simple body-centered-cubic high-pressure phases of ammonia monohydrate and ammonia dihydrate, this is the first complex molecular structure of any of the high-pressure stoichiometric ammonia hydrates to be determined. The powder structure solution is complemented by an ab initio structure prediction using density functional theory which gives an almost identical hydrogen bonding network. PMID:19754191

Fortes, A Dominic; Suard, Emmanuelle; Leme-Cailleau, Marie-Hlne; Pickard, Christopher J; Needs, Richard J

2009-09-23

199

Method of Binding Structural Material.  

National Technical Information Service (NTIS)

A structural material of a polystyrene base and the reaction product of the polystyrene base and a solid phosphate ceramic. The ceramic is applied as a slurry which includes one or more of a metal oxide or a metal hydroxide with a source of phosphate to p...

A. L. Antink A. S. Wagh

2005-01-01

200

Crystal growth and third order NLO properties of a photonic material  

NASA Astrophysics Data System (ADS)

Organic compound 1-(4-bromophenyl)-3-(4-N, N dimethylaminophenyl) prop-2-en-1-one [BDPP] was synthesized using Claisen-Schmidt condensation reaction method. Single crystals were grown using slow evaporation solution growth technique. The FTIR study was carried out for structural confirmation. The UV-Visible spectrum reveals that the crystal is transparent in the entire visible region and absorption takes place in the UV-region. Third order non-linearity has been explored using Z-scan technique. The material exhibits non-linear absorption which can be attributed to reverse saturable absorption. This study also exploits the optical limiting behavior of the material. The theoretical study using Mopac confirms the non-linearity of the compound at the molecular level. The structural parameters were determined by using single crystal XRD. The thermal study confirms the good thermal stability of the material.

Rajesh Kumar, P. C.; Janardhana, K.; Crasta, Vincent

2014-02-01

201

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

SciTech Connect

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 parameters. Finally, we provide a model that explains the incorporation of the membrane protein from solution into the lipid phase via a portal lamellar phase.

Wallace, E.; Dranow, D.; Laible, P. D.; Christensen, J.; Nollert, P. (Biosciences Division); (Emerald BioStructures)

2011-01-01

202

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

NASA Technical Reports Server (NTRS)

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.

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

1991-01-01

203

High temperature structural insulating material  

DOEpatents

A high temperature structural insulating material useful as a liner for cylinders of high temperature engines through the favorable combination of high service temperature (above about 800/sup 0/C), low thermal conductivity (below about 0.2 W/m/sup 0/C), and high compressive strength (above about 250 psi). The insulating material is produced by selecting hollow ceramic beads with a softening temperature above about 800/sup 0/C, a diameter within the range of 20-200 ..mu..m, and a wall thickness in the range of about 2 to 4 ..mu..m; compacting the beads and a compatible silicate binder composition under pressure and sintering conditions to provide the desired structural form with the structure having a closed-cell, compact array of bonded beads.

Chen, W.Y.

1984-07-27

204

High temperature structural insulating material  

DOEpatents

A high temperature structural insulating material useful as a liner for cylinders of high temperature engines through the favorable combination of high service temperature (above about 800.degree. C.), low thermal conductivity (below about 0.2 W/m.degree. C.), and high compressive strength (above about 250 psi). The insulating material is produced by selecting hollow ceramic beads with a softening temperature above about 800.degree. C., a diameter within the range of 20-200 .mu.m, and a wall thickness in the range of about 2-4 .mu.m; compacting the beads and a compatible silicate binder composition under pressure and sintering conditions to provide the desired structural form with the structure having a closed-cell, compact array of bonded beads.

Chen, Wayne Y. (Munster, IN)

1987-01-01

205

Crystal Structure of Uronate Dehydrogenase from Agrobacterium tumefaciens*  

PubMed Central

Uronate dehydrogenase from Agrobacterium tumefaciens (AtUdh) belongs to the short-chain dehydrogenase/reductase superfamily and catalyzes the oxidation of d-galacturonic acid and d-glucuronic acid with NAD+ as a cofactor. We have determined the crystal structures of an apo-form of AtUdh, a ternary form in complex with NADH and product (substrate-soaked structure), and an inactive Y136A mutant in complex with NAD+. The crystal structures suggest AtUdh to be a homohexamer, which has also been observed to be the major form in solution. The monomer contains a Rossmann fold, essential for nucleotide binding and a common feature of the short-chain dehydrogenase/reductase family enzymes. The ternary complex structure reveals a product, d-galactaro-1,5-lactone, which is bound above the nicotinamide ring. This product rearranges in solution to d-galactaro-1,4-lactone as verified by mass spectrometry analysis, which agrees with our previous NMR study. The crystal structure of the mutant with the catalytic residue Tyr-136 substituted with alanine shows changes in the position of Ile-74 and Ser-75. This probably altered the binding of the nicotinamide end of NAD+, which was not visible in the electron density map. The structures presented provide novel insights into cofactor and substrate binding and the reaction mechanism of AtUdh. This information can be applied to the design of efficient microbial conversion of d-galacturonic acid-based waste materials.

Parkkinen, Tarja; Boer, Harry; Janis, Janne; Andberg, Martina; Penttila, Merja; Koivula, Anu; Rouvinen, Juha

2011-01-01

206

Observations on the crystal structures of lueshite  

NASA Astrophysics Data System (ADS)

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.

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

2014-06-01

207

The crystal structure of diphtheria toxin  

Microsoft Academic Search

The crystal structure of the diphtheria toxin dimer at 2.5 resolution reveals a Y-shaped molecule of three domains. The catalytic domain, called fragment A, is of the alpha + beta type. Fragment B actually consists of two domains. The transmembrane domain consists of nine alpha-helices, two pairs of which are unusually apolar and may participate in pH-triggered membrane insertion

Seunghyon Choe; Melanie J. Bennett; Gary Fujii; Paul M. G. Curmi; Katherine A. Kantardjieff; R. John Collier; David Eisenberg

1992-01-01

208

Crystal Structures of the ?2-Adrenergic Receptor  

NASA Astrophysics Data System (ADS)

G protein coupled receptors (GPCRs) constitute the largest family of membrane proteins in the human genome, and are responsible for the majority of signal transduction events involving hormones and neuro-transmitters across the cell membrane. GPCRs that bind to diffusible ligands have low natural abundance, are relatively unstable in detergents, and display basal G protein activation even in the absence of ligands. To overcome these problems two approaches were taken to obtain crystal structures of the ?2-adrenergic receptor (?2AR), a well-characterized GPCR that binds cate-cholamine hormones. The receptor was bound to the partial inverse agonist carazolol and co-crystallized with a Fab made to a three-dimensional epitope formed by the third intracellular loop (ICL3), or by replacement of ICL3 with T4 lysozyme. Small crystals were obtained in lipid bicelles (?2AR-Fab) or lipidic cubic phase (?2AR-T4 lysozyme), and diffraction data were obtained using microfocus technology. The structures provide insights into the basal activity of the receptor, the structural features that enable binding of diffusible ligands, and the coupling between ligand binding and G-protein activation.

Weis, William I.; Rosenbaum, Daniel M.; Rasmussen, Sren G. F.; Choi, Hee-Jung; Thian, Foon Sun; Kobilka, Tong Sun; Yao, Xiao-Jie; Day, Peter W.; Parnot, Charles; Fung, Juan J.; Ratnala, Venkata R. P.; Kobilka, Brian K.; Cherezov, Vadim; Hanson, Michael A.; Kuhn, Peter; Stevens, Raymond C.; Edwards, Patricia C.; Schertler, Gebhard F. X.; Burghammer, Manfred; Sanishvili, Ruslan; Fischetti, Robert F.; Masood, Asna; Rohrer, Daniel K.

209

The crystal structure of Hiortdahlite II  

Microsoft Academic Search

Summary The crystal structure of Hiortdahlite II [triclinic P1,a = 11.012(6),b = 10.342(3),c = 7.359 (3) ,a = 89.92(2), = 109.21(5),y = 90.06(3)], was determined and refined using 1793 reflections toR1 = 0.069 and R2 = 0.066. The results of the structural study indicated that hiortdahlite II presents the modules which characterize the whole family of minerals related to

S. Merlino; N. Perchiazzi

1987-01-01

210

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

ERIC Educational Resources Information Center

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)

Chesick, John P.

1989-01-01

211

Crystal Structure, Chemical Binding, and Lattice Properties  

NASA Astrophysics Data System (ADS)

This chapter starts with an overview of the ZnO crystal structure and its conjunction to the chemical binding. ZnO commonly occurs in the wurtzite structure. This fact is closely related to its tetrahedral bond symmetry and its prominent bond polarity. The main part of the first section deals with the ZnO wurtzite crystal lattice, its symmetry properties, and its geometrical parameters. Besides wurtzite ZnO, the other polytypes, zinc-blende and rocksalt ZnO are also briefly discussed. Subsequently, lattice constant variations and crystal lattice deformations are treated. This discussion starts with static lattice constant variations, induced by temperature or by pressure, as well as strain-induced static lattice deformation, which reduces the crystal symmetry. The impact of this symmetry reduction on the electrical polarization is the piezo effect, which is very much pronounced in ZnO and is exploited in many applications. See also Chap. 13. Dynamic lattice deformations manifest themselves as phonons and, in case of doping, as phonon-plasmon mixed states. The section devoted to phonons starts with a consideration of the vibration eigenmodes and their dispersion curves. Special attention is paid to the investigation of phonons by optical spectroscopy. The methods applied for this purpose are infrared spectroscopy and, more often, Raman spectroscopy. The latter method is very common for the structural quality assessment of ZnO bulk crystals and layers; it is also frequently used for the study of the incorporation of dopant and alloying atoms in the ZnO crystal lattice. Thus, it plays an important role with regard to possible optoelectronics and spintronics applications of ZnO. The final section of this chapter focuses on phonon-plasmon mixed states. These eigenstates occur in doped ZnO due to the strong coupling between collective free-carrier oscillations and lattice vibrations, which occurs due to the high bond polarity. Owing to the direct correlation of the plasmon-phonon modes to the electronic doping, they are an inherent property of ZnO samples, when applied in (opto-) electronics and spintronics. See also Chap. 12.

Geurts, J.

212

Crystallization and Characterization of Galdieria sulphuraria RUBISCO in Two Crystal Forms: Structural Phase Transition Observed in P21 Crystal Form  

Microsoft Academic Search

We have isolated ribulose-1,5-bisphosphate-carboxylase\\/oxygenase (RUBISCO) from the red algae Galdieria Sulphuraria . The protein crystallized in two different crystal forms, the I422 crystal form being obtained from hi gh salt and the P2 1 crystal form being obtained from lower concentration of salt and PEG. We report here the crystallization, preliminary stages of structure determination and t he detection of

Michael Baranowski; Boguslaw Stec

2007-01-01

213

Crystal structure and electrochemical properties of rare earth non-stoichiometric AB5-type alloy as negative electrode material in Ni-MH battery  

NASA Astrophysics Data System (ADS)

The La 0.85Mg xNi 4.5Co 0.35Al 0.15 (0.05? x?0.35) system compounds have been prepared by arc melting method under Ar atmosphere. X-ray diffraction (XRD) analysis reveals that the as-prepared alloys have different lattice parameters and cell volumes. The electrochemical properties of these alloys have been studied through the charge-discharge recycle testing at different temperatures and discharge currents. It is found that the La 0.85Mg 0.25Ni 4.5Co 0.35Al 0.15 alloy electrode is capable of performing high-rate discharge. Moreover, it has very excellent electrochemical properties as negative electrode materials in Ni-MH battery at low temperature, even at -40C.

Zhang, Xinbo; Chai, Yujun; Yin, Wenya; Zhao, Minshou

2004-07-01

214

Syntheses and crystal structures of several novel alkylammonium iodobismuthate materials containing the 1,3-bis-(4-piperidinium)propane cation  

SciTech Connect

The inorganic-organic salts (H{sub 2}TMDP){sub 3}(Bi{sub 2}I{sub 9}){sub 2} (1), (H{sub 2}TMDP){sub 2}(Bi{sub 4}I{sub 16}).2EtOH (2), (H{sub 2}TMDP){sub 2}(Bi{sub 6}I{sub 22}).2EtOH (3), and (H{sub 2}TMDP){sub 2}(Bi{sub 6}I{sub 22}) (4) were synthesized and structurally characterized from the solvothermal reaction of 1,3-bis-(4-piperidyl)propane (TMDP) and BiI{sub 3} by adjusting the relative ratio of the reactants. The anions of the compounds consist of 2 (1), 4 (2), or 6 (3 and 4) BiI{sub 6} polyhedra, which are joined by face- (1) or edge-sharing (2-4) to form discrete anions. The size of the discrete anion, in terms of the number of connected polyhedra, is observed to increase as the ratio of BiI{sub 3} to TMDP is increased. A related compound (H{sub 2}TMDP)(Bi{sub 3}I{sub 11}).(H{sub 2}O) (5) was synthesized and structurally characterized using the same two reactants in the presence of HF. The anion of 5 is polymeric rather than discrete, with a trioctahedral repeat unit.

Goforth, Andrea M. [Department of Chemistry and Biochemistry, Graduate Sciences Research Center, University of South Carolina, 631 Sumter Street, Columbia, SC 29208 (United States); Peterson, LeRoy [Department of Chemistry, Francis Marion University, Florence, SC 29501 (United States); Smith, Mark D. [Department of Chemistry and Biochemistry, Graduate Sciences Research Center, The University of South Carolina, 631 Sumter Street, Columbia, SC 29208 (United States); Loye, Hans-Conrad zur [Department of Chemistry and Biochemistry, Graduate Sciences Research Center, University of South Carolina, 631 Sumter Street, Columbia, SC 29208 (United States)]. E-mail: zurloye@mail.chem.sc.edu

2005-11-15

215

[Band electronic structures and crystal packing forces  

SciTech Connect

We investigated the electronic and structural properties of low-dimensional materials and explored the structure-property correlations governing their physical properties. Progress was made on how to interpret the scanning tunneling microscopy and atomic force microscopy images of layered materials and on how to account for charge density wave instabilities in 2-D metals. Materials studied included transition metal chalcogenides, transition metal halides, organic conducting salts, Mo bronzes, A[sub 2]PdH[sub 2], fullerenes, squarate tetrahydrate polymers Fe, Cu(C[sub 4]O[sub 4])4[center dot]H[sub 2]O, BEDT salts, etc.

Not Available

1993-01-01

216

Crystal structures of carbonates up to Mbar pressures determined by single crystal synchrotron radiation diffraction  

NASA Astrophysics Data System (ADS)

The recent improvements at synchrotron beamlines, currently allow single crystal diffraction experiments at extreme pressures and temperatures [1,2] on very small single crystal domains. We successfully applied such technique to determine the crystal structure adopted by carbonates at mantle pressures. The knowledge of carbon-bearing phases is in fact fundamental for any quantitative modelling of global carbon cycle. The major technical difficulty arises after first order transitions or decomposition reactions, since original crystal (apx. 10x10x5 ?m3) is transformed in much smaller crystalline domains often with random orientation. The use of 3D reciprocal space visualization software and the improved resolution of new generation flat panel detectors, however, allow both identification and integration of each single crystal domain, with suitable accuracy for ab-initio structure solution, performed with direct and charge-flipping methods and successive structure refinements. The results obtained on carbonates, indicate two major crystal-chemistry trends established at high pressures. The CO32- units, planar and parallel in ambient pressure calcite and dolomite structures, becomes non parallel in calcite- and dolomite-II and III phases, allowing more flexibility in the structures with possibility to accommodate strain arising from different cation sizes (Ca and Mg in particular). Dolomite-III is therefore also observed to be thermodynamically stable at lower mantle pressures and temperatures, differently from dolomite, which undergoes decomposition into pure end-members in upper mantle. At higher pressure, towards Mbar (lowermost mantle and D'' region) in agreement with theoretical calculations [3,4] and other experimental results [5], carbon coordination transform into 4-fold CO4 units, with different polymerisation in the structure depending on carbonate composition. The second important crystal chemistry feature detected is related to Fe2+ in Fe-bearing magnesite, which spontaneously oxidises at HP/HT, forming Fe3+ carbonates, Fe3+ oxides and reduced carbon (diamonds). Single crystal diffraction approach allowed full structure determination of these phases, yielding to the discovery of few unpredicted structures, such as Mg2Fe2C4O13 and Fe13O19, which can be well reproduced in different experiments. Mg2Fe2C4O13 carbonate present truncated chain C4O13 groups, and Fe13O19 oxide, whose stoichiometry is intermediate between magnetite and hematite, is a one-layer structure, with features encountered in superconducting materials. The results fully support the ideas of unexpected complexities in the mineralogy of the lowermost mantle, and single crystal technique, once properly optimized in ad-hoc synchrotron beamlines, is fundamental for extracting accurate structural information, otherwise rarely accessible with other experimental techniques. References: [1] Merlini M., Hanfland M. (2013). Single crystal diffraction at Mbar conditions by synchrotron radiation. High Pressure Research, in press. [2] Dubrovinsky et al., (2010). High Pressure Research, 30, 620-633. [3] Arapan et al. (1997). Phys. Rev. Lett., 98, 268501. [4] Oganov et al. (2008) EPSL, 273, 38-47. [5] Boulard et al. (2011) PNAS, 108, 5184-5187.

Merlini, M.

2013-12-01

217

Polymerized lyotropic liquid crystals as contact lens materials  

Microsoft Academic Search

When an aqueous solution of a hydrophilic monomer such as 2-hydroxyethylmetharylate (HEMA) is mixed with a surfactant at the correct proportions, the components self-assemble into a lytropic liquid crystal comprising a highly ordered periodic microstructure, and polymerization of the monomer and removal of the surfactant results in a macroporous hydrogel of potential importance as a material for contact lenses and

David M. Anderson; Pelle Strm

1991-01-01

218

Geometry of Crystal Structure with Defects. I. Euclidean Picture  

NASA Astrophysics Data System (ADS)

Continuously distributed defects of crystal structure are considered. The starting point is the Euclidean geometry of the ideal crystal lattice and the topological description of the distortion of the crystal structure. It is shown how the non-Euclidean geometry of distorted crystal structure, as well as the basic assumptions of the phenomenological plasticity theory concerning the deformation of a continuum, are related to those theories. A form for an affine connection describing continuously distributed dislocations is proposed.

Trzesowski, Andrzej

1987-04-01

219

Constructing 3D crystal templates for photonic band gap materials using holographic optical tweezers.  

PubMed

A simple and robust method is presented for the construction of 3-dimensional crystals from silica and polystyrene microspheres. The crystals are suitable for use as templates in the production of three-dimensional photonic band gap (PBG) materials. Manipulation of the microspheres was achieved using a dynamic holographic assembler (DHA) consisting of computer controlled holographic optical tweezers. Attachment of the microspheres was achieved by adjusting their colloidal interactions during assembly. The method is demonstrated by constructing a variety of 3-dimensional crystals using spheres ranging in size from 3 microm down to 800 nm. A major advantage of the technique is that it may be used to build structures that cannot be made using self-assembly. This is illustrated through the construction of crystals in which line defects have been deliberately included, and by building simple cubic structures. PMID:18711539

Benito, D C; Carberry, D M; Simpson, S H; Gibson, G M; Padgett, M J; Rarity, J G; Miles, M J; Hanna, S

2008-08-18

220

The First Mammalian Aldehyde Oxidase Crystal Structure  

PubMed Central

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 ?. 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.

Coelho, Catarina; Mahro, Martin; Trincao, Jose; Carvalho, Alexandra T. P.; Ramos, Maria Joao; Terao, Mineko; Garattini, Enrico; Leimkuhler, Silke; Romao, Maria Joao

2012-01-01

221

Design and functionality of colloidal-crystal-templated materials--chemical applications of inverse opals.  

PubMed

Templating with colloidal crystals composed of monodisperse spheres is a convenient chemical method to obtain porous materials with well-ordered periodicity and interconnected pore systems. The three-dimensionally ordered macroporous (3DOM) products or inverse opals are of interest for numerous applications, both for the optical properties related to structural color of these photonic crystal materials and because of their bicontinuous nanostructure, i.e., a continuous nanostructured skeleton with large interfacial area and a three-dimensionally interconnected pore system with low tortuosity. This review outlines various synthetic methods used to control the morphology of 3DOM materials with different compositions. It highlights aspects of the choice of colloidal particles, assembly of the colloidal crystal template, infiltration and processing, template removal, and other necessary modifications to enhance the functionality of the materials. It also considers syntheses within the confinement of 3DOM materials and summarizes characterization methods that are particularly useful in the analysis of 3DOM materials. The review then discusses chemical applications of 3DOM materials, namely sorption and controlled release, optical and electrochemical sensors, solar cells, lithium ion batteries, supercapacitors, fuel cells, and environmental and chemical fuel catalysis. A focus is on structural features and materials properties that enable these applications. PMID:23079696

Stein, Andreas; Wilson, Benjamin E; Rudisill, Stephen G

2013-04-01

222

Crystal structure of the dynein motor domain.  

PubMed

Dyneins are microtubule-based motor proteins that power ciliary beating, transport intracellular cargos, and help to construct the mitotic spindle. Evolved from ring-shaped hexameric AAA-family adenosine triphosphatases (ATPases), dynein's large size and complexity have posed challenges for understanding its structure and mechanism. Here, we present a 6 angstrom crystal structure of a functional dimer of two ~300-kilodalton motor domains of yeast cytoplasmic dynein. The structure reveals an unusual asymmetric arrangement of ATPase domains in the ring-shaped motor domain, the manner in which the mechanical element interacts with the ATPase ring, and an unexpected interaction between two coiled coils that create a base for the microtubule binding domain. The arrangement of these elements provides clues as to how adenosine triphosphate-driven conformational changes might be transmitted across the motor domain. PMID:21330489

Carter, Andrew P; Cho, Carol; Jin, Lan; Vale, Ronald D

2011-03-01

223

Electronic structure of molecular crystals containing edge dislocations  

NASA Astrophysics Data System (ADS)

An attempt to model the electronic structure of molecular crystals containing an edge dislocation at the ab initio Hartree-Fock level is performed. The experimentally determined configurations for edge-type dislocations with the Burgers vector [001] in crystalline cyclotrimethylene trinitramine (RDX) and pentaetythritol tetranitrate (PETN) are theoretically simulated. It is shown that a shear stress, induced by the dislocations, produces local electronic states in the fundamental band gap of the crystal. These states are mainly formed by molecular orbitals of critical bonds (which are the N-NO2 group in RDX and the O-NO2 group in PETN) responsible for the stability of the materials. Optical absorption attributed to these electronic states is predicted and compared to the available experimental data. Properties of the defective solids are compared with those of the perfect crystals. Correlation of the electronic structure and sensitivity of the materials to initiation of a chemical reaction as well as some practical applications of the obtained results are discussed.

Kuklja, Maija M.; Kunz, A. Barry

2001-05-01

224

The Crystal Structure of Triuranyl Diphosphate Tetrahydrate  

Microsoft Academic Search

The hydrated neutral uranyl phosphate, (UO2)3(PO4)2(H2O)4, was synthesized by hydrothermal methods. Intensity data were collected using MoK? radiation and a CCD-based area detector. The crystal structure was solved by direct methods and refined by full-matrix least-squares techniques to agreement indices wR2=0.116 for all data, and R1=0.040, calculated for the 2764 unique observed reflections (?Fo??4?F). The compound is orthorhombic, space group

Andrew J. Locock; Peter C. Burns

2002-01-01

225

Crystal Structure of Marburg Virus VP24.  

PubMed

The VP24 protein plays an essential, albeit poorly understood role in the filovirus life cycle. VP24 is only 30% identical between Marburg virus and the ebolaviruses. Furthermore, VP24 from the ebolaviruses is immunosuppressive, while that of Marburg virus is not. The crystal structure of Marburg virus VP24, presented here, reveals that although the core is similar between the viral genera, Marburg VP24 is distinguished by a projecting ?-shelf and an alternate conformation of the N-terminal polypeptide. PMID:24574400

Zhang, Adrianna P P; Bornholdt, Zachary A; Abelson, Dafna M; Saphire, Erica Ollmann

2014-05-01

226

Elasticity of some mantle crystal structures. II.  

NASA Technical Reports Server (NTRS)

The single-crystal elastic constants are determined as a function of pressure and temperature for rutile structure germanium dioxide (GeO2). The data are qualitatively similar to those of rutile TiO2 measured by Manghnani (1969). The compressibility in the c direction is less than one-half that in the a direction, the pressure derivative of the shear constant is negative, and the pressure derivative of the bulk modulus has a relatively high value of about 6.2. According to an elastic strain energy theory, the negative shear modulus derivative implies that the kinetic barrier to diffusion decreases with increasing pressure.

Wang, H.; Simmons, G.

1973-01-01

227

Memory and topological frustration in nematic liquid crystals confined in porous materials.  

PubMed

Orientational ordering is key to functional materials with switching capability, such as nematic liquid crystals and ferromagnetic and ferroelectric materials. We explored the confinement of nematic liquid crystals in bicontinuous porous structures with smooth surfaces that locally impose normal orientational order on the liquid crystal. We find that frustration leads to a high density of topological defect lines permeating the porous structures, and that most defect lines are made stable by looping around solid portions of the confining material. Because many defect trajectories are possible, these systems are highly metastable and efficient in memorizing the alignment forced by external fields. Such memory effects have their origin in the topology of the confining surface and are maximized in a simple periodic bicontinuous cubic structure. We also show that nematic liquid crystals in random porous networks exhibit a disorder-induced slowing-down typical of glasses that originates from activated collisions and rearrangements of defect lines. Our findings offer the possibility to functionalize orientationally ordered materials through topological confinement. PMID:21423186

Araki, Takeaki; Buscaglia, Marco; Bellini, Tommaso; Tanaka, Hajime

2011-04-01

228

Lightweight single crystal silicon opto-mechanical structures  

NASA Astrophysics Data System (ADS)

Single Crystal Silicon (SCSi) is proving to be an excellent material for the fabrication of lightweight optical components for use in space. As part of the feasibility studies performed prior to space flight applications, it is important to determine the mechanical properties of complex structures manufactured from individual sections of SCSi. As an additional integral building block for future multi-component SCSi structures, the behavior of the McCarter Machine proprietary frit-bonded metal insert technology was examined. Here we report vibration test results, the objective of which was to measure the structural damping characteristics of a typical silicon structure and verify its structural stability after exposure to random vibration. The tests were designed to better understand SCSi, not only as a mirror substrate, but also as a structural material. The success of this test, combined with the already proven McCarter Machine manufacturing techniques, give us the ability to now manufacture new lightweight and stable opto-mechanical assemblies entirely out of SCSi. But since requirements for larger and more sophisticated SCSi structures are limited by the practical size of available boules, the behavior of these frit-bonded SCSi structures needs to be better understood. This understanding will be obtained from planned testing of larger frit bonded SCSi opto-mechanical structural components and assemblies.

Paquin, Roger A.; McCarter, Douglas R.

2009-05-01

229

Microstructural characterization of sputtered garnet materials and all-garnet magnetic heterostructures: establishing the technology for magnetic photonic crystal fabrication  

Microsoft Academic Search

We have established a set of technologies for the deposition and annealing of magneto-optic ferrite and paramagnetic garnets, as well as multilayer nanostructures which are based on these materials, for use in magnetic photonic crystals. Transmission electron microscope analysis has been performed to investigate the structure of both amorphous and crystallized garnet layers, nanocrystallites and layer interfaces within all-garnet heterostructures.

Mikhail Vasiliev; P. C. Wo; Kamal Alameh; Paul Munroe; Zonghan Xie; V. A. Kotov; V. I. Burkov

2009-01-01

230

Crystal morphology variation in inkjet-printed organic materials  

NASA Astrophysics Data System (ADS)

The recent commercialization of piezoelectric-based drop-on-demand inkjet printers provides an additive processing platform for producing and micropatterning organic crystal structures. We report an inkjet printing approach where macro- and nano-scale energetic composites composed of cyclotrimethylenetrinitramine (RDX) crystals dispersed in a cellulose acetate butyrate (CAB) matrix are produced by direct phase transformation from organic solvent-based all-liquid inks. The characterization of printed composites illustrates distinct morphological changes dependent on ink deposition parameters. When 10 pL ink droplets rapidly formed a liquid pool, a coffee ring structure containing dendritic RDX crystals was produced. By increasing the substrate temperature, and consequently the evaporation rate of the pooled ink, the coffee ring structure was mitigated and shorter dendrites from up to 1 to 0.2 mm with closer arm spacing from 15 to 1 ?m were produced. When the nucleation and growth of RDX and CAB were confined within the evaporating droplets, a granular structure containing nanoscale RDX crystals was produced. The results suggest that evaporation rate and microfluidic droplet confinement can effectively be used to tailor the morphology of inkjet-printed energetic composites.

Ihnen, Andrew C.; Petrock, Anne M.; Chou, Tsengming; Samuels, Phillip J.; Fuchs, Brian E.; Lee, Woo Y.

2011-11-01

231

Structural materials for space applications  

NASA Technical Reports Server (NTRS)

The long-term performance of structural materials in the space environment is a key research activity within NASA. The primary concerns for materials in low Earth orbit (LEO) are atomic oxygen erosion and space debris impact. Atomic oxygen studies have included both laboratory exposures in atomic oxygen facilities and flight exposures using the Shuttle. Characterization of atomic oxygen interaction with materials has included surface recession rates, residual mechanical properties, optical property measurements, and surface analyses to establish chemical changes. The Long Duration Exposure Facility (LDEF) is scheduled to be retrieved in 1989 and is expected to provide a wealth of data on atomic oxygen erosion in space. Hypervelocity impact studies have been conducted to establish damage mechanisms and changes in mechanical properties. Samples from LDEF will be analyzed to determine the severity of space debris impact on coatings, films, and composites. Spacecraft placed in geosynchronous Earth orbit (GEO) will be subjected to high doses of ionizing radiation which for long term exposures will exceed the damage threshold of many polymeric materials. Radiation interaction with polymers can result in chain scission and/or cross-linking. The formation of low molecular weight products in the epoxy plasticize the matrix at elevated temperatures and embrittle the matrix at low temperatures. This affects both the matrix-dominated mechanical properties and the dimensional stability of the composite. Embrittlement of the matrix at low temperatures results in enhanced matrix microcracking during thermal cycling. Matrix microcracking changes the coefficient of thermal expansion (CTE) of composite laminates and produces permanent length changes. Residual stress calculations were performed to estimate the conditions necessary for microcrack development in unirradiated and irradiated composites. The effects of UV and electron exposure on the optical properties of transparent polymer films were also examined to establish the optimum chemical structure for good radiation resistance. Thoughts on approaches to establishing accelerated testing procedures are discussed.

Tenney, Darrel R.

1989-01-01

232

Band structure of phononic crystals with general damping  

NASA Astrophysics Data System (ADS)

In this paper, we present theoretical formalisms for the study of wave dispersion in damped elastic periodic materials. We adopt the well known structural dynamics techniques of modal analysis and state-space transformation and formulate them for the Bloch wave propagation problem. First, we consider a one-dimensional lumped parameter model of a phononic crystal consisting of two masses in the unit cell whereby the masses are connected by springs and dashpot viscous dampers. We then extend our analysis to the study of a two-dimensional phononic crystal, modeled as a dissipative elastic continuum, and consisting of a periodic arrangement of square inclusions distributed in a matrix base material. For our damping model, we consider both proportional damping and general damping. Our results demonstrate the effects of damping on the frequency band structure for various types and levels of damping. In particular, we reveal two intriguing phenomena: branch overtaking and branch cut-off. The former may result in an abrupt drop in the relative band gap size, and the latter implies an opening of full or partial wavenumber (wave vector) band gaps. Following our frequency band structure analysis, we illustrate the concept of a damping ratio band structure.

Hussein, Mahmoud I.; Frazier, Michael J.

2010-11-01

233

Reactive liquid crystal materials for optically anisotropic patterned retarders  

NASA Astrophysics Data System (ADS)

Merck has developed a range of reactive liquid crystal materials (Reactive Mesogens) that are designed to form thin, birefringent, coatable films for optical applications. Reactive Mesogen (RM) films are typically coated from solution and polymerized in-situ to form thin, optics-grade coatings. Merck RM materials are customized formulations including reactive liquid crystals, surfactants, photoinitiators and other proprietary additives. Merck have optimized the materials to achieve the optimum physical performance in each application. In this paper we focus on the optimization of RM materials to achieve the finest patterning resolution and defined feature shape whilst maintaining good physical properties of the films. Several conventional trade-offs are investigated and circumvented using novel material concepts. Different methods of patterning RM materials are discussed and the merits of each considered. Thermal annealing of non-polymerized regions can create isotropic islands within the polymerized anisotropic matrix. Alternatively, the non polymerized material can be re-dissolved in the coating solvent and rinsed away. Each of these techniques has benefits depending on the processing conditions and these are discussed in depth.

Harding, Richard; Gardiner, Iain; Yoon, Hyun-Jin; Perrett, Tara; Parri, Owain; Skjonnemand, Karl

2008-11-01

234

Crystal structure of the Baykovite mineral  

SciTech Connect

The X-ray crystal structure of baykovite, [Ca{sub 1.07}Mg{sub 0.62}Ti{sub 0.31}(Al{sub 0.55}Si{sub 0.45}){sub 2}O{sub 6}][Al(Mg{sub 0.77}Ti{sub 1.17}Al{sub 0.06}){sub 2}O{sub 4}] - a mineral of the enigmatite structural group - was determined: sp gr. P{bar 1}, a = 10.425(2), b = 10.799(2), c = 8.924(2) {Angstrom}, {alpha} = 105.98(2), {beta} = 96.05(2), {gamma} = 124.76(1){degrees}, V= 748.425, Z= 2, and R = 0.046. Baykovite is shown to be close to rhoenite varieties, which are characterized by their anomalous composition with a high content of titanium in two oxidation states: Ti{sup +3} and Ti{sup +4}. The structures of enigmatite-group compounds are described as disomatic structures formed from spinel and pyroxene moieties. A scheme of cation distribution over the equivalent positions in the enigmatite-group structures is proposed based on the assumption that individual fragments inherit the main features of the parent structures. 8 refs., 2 figs., 5 tabs.

Arakcheeva, A.V. [Baikov Institute of Metallurgy, Moscow (Russian Federation)

1995-03-01

235

Method of binding structural material  

DOEpatents

A structural material of a polystyrene base and the reaction product of the polystyrene base and a solid phosphate ceramic. The ceramic is applied as a slurry which includes one or more of a metal oxide or a metal hydroxide with a source of phosphate to produce a phosphate ceramic and a poly (acrylic acid or acrylate) or combinations or salts thereof and polystyrene or MgO applied to the polystyrene base and allowed to cure so that the dried aqueous slurry chemically bonds to the polystyrene base. A method is also disclosed of applying the slurry to the polystyrene base.

Wagh, Arun S. (Orland Park, IL); Antink, Allison L. (Bolingbrook, IL)

2007-12-25

236

Synthesis and structural characterization of new microporous framework materials  

Microsoft Academic Search

Porous solids have attracted a great amount of attention in the last few years because of not only their interesting crystal structures but also their potential applications in catalysis, ion-exchange and sorption. In this dissertation research, the exploratory synthesis of novel crystalline microporous materials was studied in detail. The types of open frameworks of interest include organically templated metal phosphates

Hyunsoo Park

2007-01-01

237

Structural and spectroscopic studies on calcium succinate single crystals  

NASA Astrophysics Data System (ADS)

Calcium succinate crystals have been grown by gel aided solution growth technique. The structure of the crystal is solved by single crystal XRD analysis. The Crystal structure of the title compound is triclinic having space group P(1) Powder XRD studies confirmed the good crystalline nature of the sample. The different functional groups and their assigned vibrations are discussed by FT-IR and FT Raman spectroscopic studies.

Binitha, M. P.; Pradyumnan, P. P.

2014-04-01

238

Crystal structure of yeast Sco1.  

PubMed

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-A 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. PMID:16570183

Abajian, Carnie; Rosenzweig, Amy C

2006-06-01

239

Structural contribution to the roughness of supersmooth crystal surface  

SciTech Connect

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.

Butashin, A. V.; Muslimov, A. E., E-mail: amuslimov@mail.ru; Kanevsky, V. M.; Deryabin, A. N.; Pavlov, V. A.; Asadchikov, V. E. [Russian Academy of Sciences, Shubnikov Institute of Crystallography (Russian Federation)

2013-05-15

240

Structural contribution to the roughness of supersmooth crystal surface  

NASA Astrophysics Data System (ADS)

Technological advances in processing crystals (Si, sapphire ?-Al2O3, SiC, GaN, LiNbO3, SrTiO3, 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 1 and 10 10 ?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.

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

2013-05-01

241

Selective crystallization with preferred lithium-ion storage capability of inorganic materials  

PubMed Central

Lithium-ion batteries are supposed to be a key method to make a more efficient use of energy. In the past decade, nanostructured electrode materials have been extensively studied and have presented the opportunity to achieve superior performance for the next-generation batteries which require higher energy and power densities and longer cycle life. In this article, we reviewed recent research activities on selective crystallization of inorganic materials into nanostructured electrodes for lithium-ion batteries and discuss how selective crystallization can improve the electrode performance of materials; for example, selective exposure of surfaces normal to the ionic diffusion paths can greatly enhance the ion conductivity of insertion-type materials; crystallization of alloying-type materials into nanowire arrays has proven to be a good solution to the electrode pulverization problem; and constructing conversion-type materials into hollow structures is an effective approach to buffer the volume variation during cycling. The major goal of this review is to demonstrate the importance of crystallization in energy storage applications.

2012-01-01

242

Crystal structure of human nicotinamide riboside kinase.  

PubMed

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

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

2007-08-01

243

Crystal Structure of Human Nicotinamide Riboside Kinase  

SciTech Connect

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.

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

2007-01-01

244

Crystallization of Stretched Polyimides: A Structure-Property Study  

NASA Technical Reports Server (NTRS)

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.

Hinkley, Jeffrey A.; Dezern, James F.

2002-01-01

245

Biomolecular crystals for material applications and a mechanistic study of an iron oxide nanoparticle synthesis  

NASA Astrophysics Data System (ADS)

The three projects within this work address the difficulties of controlling biomolecular crystal formats (i.e. size and shape), producing 3-D ordered composite materials from biomolecular crystal templates, and understanding the mechanism of a practical iron oxide synthesis. The unifying thread consistent throughout these three topics is the development of methods to manipulate nanomaterials using a bottom-up approach. Biomolecular crystals are nanometer to millimeter sized crystals that have well ordered mesoporous solvent channels. The overall physical dimensions of these crystals are highly dependent on crystallization conditions. The controlled growth of micro- and nanoprotein crystals was studied to provide new pathways for creating smaller crystalline protein materials. This method produced tetragonal hen egg-white lysozyme crystals (250--100,000 nm) with near monodisperse size distributions (<15%). With this degree of control, existing protein crystal applications such as drug delivery and analytical sensors can reach their full potential. Applications for larger crystals with inherently ubiquitous pore structures could extend to materials used for membranes or templates. In this work, the porous structure of larger cowpea mosaic virus crystals was used to template metal nanoparticle growth within the body centered cubic crystalline network. The final composite material was found to have long range ordering of palladium and platinum nonocrystal aggregates (10nm) with symmetry consistent to the virus template. Nanoparticle synthesis itself is an immense field of study with an array of diverse applications. The final piece of this work investigates the mechanism behind a previously developed iron oxide synthesis to gain more understanding and direction to future synthesis strategies. The particle growth mechanism was found to proceed by the formation of a solvated iron(III)oleate complex followed by a reduction of iron (III) to iron (II). This unstable iron(II) nucleates to form a wustite (FeO) core which serves as an epitaxial surface for the magnetite (Fe3O4) shell growth. This method produces spherical particles (6-60nm) with relative size distributions of less than 15%.

Falkner, Joshua Charles

246

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

PubMed

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 (1)H 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. PMID:24810028

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

2014-09-15

247

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

NASA Astrophysics Data System (ADS)

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.

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

2014-09-01

248

Crystal Structure of Human Spermine Synthase  

PubMed Central

The crystal structures of two ternary complexes of human spermine synthase (EC 2.5.1.22), one with 5?-methylthioadenosine and spermidine and the other with 5?-methylthioadenosine and spermine, have been solved. They show that the enzyme is a dimer of two identical subunits. Each monomer has three domains: a C-terminal domain, which contains the active site and is similar in structure to spermidine synthase; a central domain made up of four ?-strands; and an N-terminal domain with remarkable structural similarity to S-adenosylmethionine decarboxylase, the enzyme that forms the aminopropyl donor substrate. Dimerization occurs mainly through interactions between the N-terminal domains. Deletion of the N-terminal domain led to a complete loss of spermine synthase activity, suggesting that dimerization may be required for activity. The structures provide an outline of the active site and a plausible model for catalysis. The active site is similar to those of spermidine synthases but has a larger substrate-binding pocket able to accommodate longer substrates. Two residues (Asp201 and Asp276) that are conserved in aminopropyltransferases appear to play a key part in the catalytic mechanism, and this role was supported by the results of site-directed mutagenesis. The spermine synthase5?-methylthioadenosine structure provides a plausible explanation for the potent inhibition of the reaction by this product and the stronger inhibition of spermine synthase compared with spermidine synthase. An analysis to trace possible evolutionary origins of spermine synthase is also described.

Wu, Hong; Min, Jinrong; Zeng, Hong; McCloskey, Diane E.; Ikeguchi, Yoshihiko; Loppnau, Peter; Michael, Anthony J.; Pegg, Anthony E.; Plotnikov, Alexander N.

2008-01-01

249

Advanced Structural Materials and Cladding  

SciTech Connect

Advanced nuclear energy systems, both fission- and fusion-based, aim to operate at higher temperatures and greater radiation exposure levels than experienced in current light water reactors. Additionally, they are envisioned to operate in coolants such as helium and sodium that allow for higher operating temperatures. Because of these unique environments, different requirements and challenges are presented for both structural materials and fuel cladding. For core and cladding applications in intermediate-temperature reactors (400-650 C), the primary candidates are 9-12Cr ferritic-martensitic steels (where the numbers represent the weight percentage of Cr in the material, i.e., 9-12 wt%) and advanced austenitic steels, adapted to maximize high temperature strength without compromising lower temperature toughness. For very high temperature reactors (>650 C), strength and oxidation resistance are more critical. In such conditions, high-temperature metals as well as ceramics and ceramic composites are candidates. For all advanced systems operating at high pressures, performance of the pressure boundary materials (i.e., those components responsible for containing the high-pressure liquids or gases that cool the reactor) is critical to reactor safety. For some reactors, pressure vessels are anticipated to be significantly larger and thicker than those used in light water reactors. The properties through the entire thickness of these components, including the effects of radiation damage as a function of damage rate, are important. For all of these advanced systems, optimizing the microstructures of candidate materials will allow for improved radiation and high-temperature performance in nuclear applications, and advanced modeling tools provide a basis for developing optimized microstructures.

Allen, Todd R. [University of Wisconsin, Madison; Burlet, H. [CEA, Grenoble, France; Nanstad, Randy K [ORNL; SAMARAS, M. [Paul Scherrer Institut, Villigen, Switzerland; Ukai, S. [Japan Atomic Energy Agency (JAEA)

2009-01-01

250

Dynamic Responses of Dispersed Ferroelectric Liquid Crystal Composite Materials  

Microsoft Academic Search

Dynamic responses of high polarization ferroelectric liquid crystalmulti walled carbon nanotubes composite material has been investigated in the wide frequency range (up to 1 MHZ). Permittivity increased by ?20% to 40% (50 Hz1 kHz range) but at high frequency >2 kHz, it was independent of carbon nano-tube concentration. The increase in permittivity is attributed to strong anisotropic interactions which enhances

Neeraj; K. K. Raina

2011-01-01

251

ND-doped mixed crystal laser material research  

Microsoft Academic Search

The mixed crystal system Y3(Al(x)Ga(1-x)5O12 was investigated at a laser host material for Nd(3+). Spectroscopic studies established that at the optimum composition a reduction by a factor of 3 in gain, as compared with YAlG (Y3Al5O12), is possible, and implying increased output energy in Q-switched operation. Mechanical and thermal properties were found to be similar to those of YAlG. Laser

W. C. Holton; D. W. Bellavance; F. J. Bruni; M. Dewit; R. K. Watts

1974-01-01

252

Morphology, crystal structure, phase transitions and blend compatibility of thermotropic liquid crystal terpolyesters  

Microsoft Academic Search

The morphology, crystal structure, phase transitions and blend compatibility of a series of semiflexible thermotropic liquid crystal terpolyesters (LCPs) were studied to understand their crystallization behavior and establish relationships between their microstructure and physical properties. Main characterization methods were electron microscopy and diffraction, and differential scanning calorimetry. The LCPs were composed of equimolar amounts of p-oxybenzoate, p-dioxyphenyl, and aliphatic segments,

Clara Lena Gonzalez-Costoso

1997-01-01

253

Liquid crystal alignment in electro-responsive nanostructured thermosetting materials based on block copolymer dispersed liquid crystal.  

PubMed

Novel well-defined nanostructured thermosetting systems were prepared by modification of a diglicydylether of bisphenol-A epoxy resin (DGEBA) with 10 or 15wt% amphiphilic poly(styrene-b-ethylene oxide) block copolymer (PSEO) and 30 or 40wt% low molecular weight liquid crystal 4'-(hexyl)-4-biphenyl-carbonitrile (HBC) using m-xylylenediamine (MXDA) as a curing agent. The competition between well-defined nanostructured materials and the ability for alignment of the liquid crystal phase in the materials obtained has been studied by atomic and electrostatic force microscopy, AFM and EFM, respectively. Based on our knowledge, this is the first time that addition of an adequate amount (10wt%) of a block copolymer to 40wt% HBC-(DGEBA/MXDA) leads to a well-organized nanostructured thermosetting system (between a hexagonal and worm-like ordered structure), which is also electro-responsive with high rate contrast. This behavior was confirmed using electrostatic force microscopy (EFM), by means of the response of the HBC liquid crystal phase to the voltage applied to the EFM tip. In contrast, though materials containing 15wt% PSEO and 30wt% HBC also form a well-defined nanostructured thermosetting system, they do not show such a high contrast between the uncharged and charged surface. PMID:21828713

Tercjak, A; Garcia, I; Mondragon, I

2008-07-01

254

Crystal structure of Junin virus nucleoprotein.  

PubMed

Junin virus (JUNV) has been identified as the aetiological agent of Argentine haemorrhagic fever (AHF), which is a serious public health problem with approximately 5 million people at risk. It is treated as a potential bioterrorism agent because of its rapid transmission by aerosols. JUNV is a negative-sense ssRNA virus that belongs to the genus Arenavirus within the family Arenaviridae, and its genomic RNA contains two segments encoding four proteins. Among these, the nucleoprotein (NP) has essential roles in viral RNA synthesis and immune suppression, but the molecular mechanisms of its actions are only partially understood. Here, we determined a 2.2 crystal structure of the C-terminal domain of JUNV NP. This structure showed high similarity to the Lassa fever virus (LASV) NP C-terminal domain. However, both the structure and function of JUNV NP showed differences compared with LASV NP. This study extends our structural insight into the negative-sense ssRNA virus NPs. PMID:23884367

Zhang, Yinjie; Li, Le; Liu, Xiang; Dong, Shishang; Wang, Wenming; Huo, Tong; Guo, Yu; Rao, Zihe; Yang, Cheng

2013-10-01

255

In situ proteolysis for protein crystallization and structure determination.  

PubMed

We tested the general applicability of in situ proteolysis to form protein crystals suitable for structure determination by adding a protease (chymotrypsin or trypsin) digestion step to crystallization trials of 55 bacterial and 14 human proteins that had proven recalcitrant to our best efforts at crystallization or structure determination. This is a work in progress; so far we determined structures of 9 bacterial proteins and the human aminoimidazole ribonucleotide synthetase (AIRS) domain. PMID:17982461

Dong, Aiping; Xu, Xiaohui; Edwards, Aled M; Chang, Changsoo; Chruszcz, Maksymilian; Cuff, Marianne; Cymborowski, Marcin; Di Leo, Rosa; Egorova, Olga; Evdokimova, Elena; Filippova, Ekaterina; Gu, Jun; Guthrie, Jennifer; Ignatchenko, Alexandr; Joachimiak, Andrzej; Klostermann, Natalie; Kim, Youngchang; Korniyenko, Yuri; Minor, Wladek; Que, Qiuni; Savchenko, Alexei; Skarina, Tatiana; Tan, Kemin; Yakunin, Alexander; Yee, Adelinda; Yim, Veronica; Zhang, Rongguang; Zheng, Hong; Akutsu, Masato; Arrowsmith, Cheryl; Avvakumov, George V; Bochkarev, Alexey; Dahlgren, Lars-Gran; Dhe-Paganon, Sirano; Dimov, Slav; Dombrovski, Ludmila; Finerty, Patrick; Flodin, Susanne; Flores, Alex; Grslund, Susanne; Hammerstrm, Martin; Herman, Maria Dolores; Hong, Bum-Soo; Hui, Raymond; Johansson, Ida; Liu, Yongson; Nilsson, Martina; Nedyalkova, Lyudmila; Nordlund, Pr; Nyman, Tomas; Min, Jinrong; Ouyang, Hui; Park, Hee-won; Qi, Chao; Rabeh, Wael; Shen, Limin; Shen, Yang; Sukumard, Deepthi; Tempel, Wolfram; Tong, Yufeng; Tresagues, Lionel; Vedadi, Masoud; Walker, John R; Weigelt, Johan; Welin, Martin; Wu, Hong; Xiao, Ting; Zeng, Hong; Zhu, Haizhong

2007-12-01

256

Crystal Growth and Other Materials Physical Researches in Space Environment  

NASA Astrophysics Data System (ADS)

Material science researches in space environment are based on reducing the effects of buoyancy driven transport, the effects of atomic oxygen, radiation, extremes of heat and cold and the ultrahigh vacuum, so as to unveil the underlying fundamental phenomena, lead maybe to new potential materials or new industrial processes and develop space techniques. Currently, research program on materials sciences in Chinese Manned Space Engineering (CMSE) is going on. More than ten projects related to crystal growth and materials processes are selected as candidates to be executed in Shenzhou spacecraft, Tiangong Space Laboratory and Chinese Space Station. In this talk, we will present some examples of the projects, which are being prepared and executed in the near future flight tasks. They are both basic and applied research, from discovery to technology.

Pan, Mingxiang

257

Datamining Protein Structure Databanks for Crystallization Patterns of Proteins  

Microsoft Academic Search

A study of 345 protein structures selected among 1500 structures determined by Nuclear Magnetic Resonance (NMR) methods, revealed useful correlation between crystallization properties and several parameters for the studied proteins. NMR methods of structure determination do not require the growth of protein crystals, and hence allow comparison of properties of proteins that have or have not been the subject of

Homayoun Valafar; James H. Prestegard; Faramarz Valafar

2002-01-01

258

Method and structure for passivating semiconductor material  

DOEpatents

A structure for passivating semiconductor material comprises a substrate of crystalline semiconductor material, a relatively thin film of carbon disposed on a surface of the crystalline material, and a layer of hydrogenated amorphous silicon deposited on the carbon film.

Pankove, Jacques I. (Princeton, NJ)

1981-01-01

259

Some Lower Valence Vanadium Fluorides: Their Crystal Distortions, Domain Structures, Modulated Structures, Ferrimagnetism, and Composition Dependence.  

ERIC Educational Resources Information Center

Describes some contemporary concepts unique to the structure of advanced solids, i.e., their crystal distortions, domain structures, modulated structures, ferrimagnetism, and composition dependence. (Author/CS)

Hong, Y. S.; And Others

1980-01-01

260

Disorder in the crystals of trans-4-fluoroazoxybenzene. Synthesis, spectral properties, crystal structures and DFT calculations  

Microsoft Academic Search

Two crystals of trans-4-fluoroazoxybenzene were obtained using two different methods. Oxidation of 4-fluoroazobenzene provided crystals of trans-4-fluoroazoxybenzene (I) consisting of two isomers; 51% alpha (ONN) and 49% beta (NNO) isomer. From trans-amino-azoxybenzenes in Schiemann reaction it were obtained crystals of trans-4-fluoro-NNO-azoxybenzenes (II, beta isomer) containing 4.7% of the alpha-isomer according to the HPLC analysis. The crystal structures of I and

Krzysztof Ejsmont; Andrzej A. Domanski; Janusz B. Kyziol; Jacek Zaleski

2005-01-01

261

Disorder in the crystals of trans-4-fluoroazoxybenzene. Synthesis, spectral properties, crystal structures and DFT calculations  

Microsoft Academic Search

Two crystals of trans-4-fluoroazoxybenzene were obtained using two different methods. Oxidation of 4-fluoroazobenzene provided crystals of trans-4-fluoroazoxybenzene (I) consisting of two isomers; 51% ? (ONN) and 49% ? (NNO) isomer. From trans-amino-azoxybenzenes in Schiemann reaction it were obtained crystals of trans-4-fluoro-NNO-azoxybenzenes (II, ? isomer) containing 4.7% of the ?-isomer according to the HPLC analysis. The crystal structures of I and

Krzysztof Ejsmont; Andrzej A. Doma?ski; Janusz B. Kyzio?; Jacek Zaleski

2005-01-01

262

Low temperature crystal structure and magnetic properties of RAl2  

NASA Astrophysics Data System (ADS)

Low temperature crystal structure and magnetic properties of RAl2 (R = Pr and Nd) have been studied using temperature dependent powder x-ray diffraction, magnetization, and heat capacity measurements. Unlike PrAl2, NdAl2 retains cubic MgCu2-type structure from room temperature down to 5 K, which is also confirmed from first principles electronic structure calculations. The magnetization measurements show both PrAl2 and NdAl2 order ferromagnetically at TC = 32 K and 77 K, respectively. However, the magnetization measurements show the former is a hard ferromagnet compared to the latter which is a soft ferromagnetic material. The magnetic entropy change obtained from heat capacity measurements at ?H = 30 kOe for PrAl2 and NdAl2 are 3.15 J mol-1 K-1 and 1.18 J mol-1 K-1, respectively.

Pathak, Arjun K.; Paudyal, D.; Gschneidner, K. A.; Pecharsky, V. K.

2014-05-01

263

Positron Annihilation and Electronic Lattice Structure in Insulator Crystals  

Microsoft Academic Search

The dimensions of the electronic lattice structure of the hexagonal quartz crystal and the fcc CaF2 crystal have been measured by resolving characteristic markings on the angular-correlation curves as observed for the two gamma quanta emitted in the annihilation of positrons with electrons in these crystals.

Werner Brandt; Grard Coussot; Robert Paulin

1969-01-01

264

Crystal structure of oligoacenes under high pressure  

SciTech Connect

We report crystal structures of anthracene, tetracene, and pentacene under pressure. Energy dispersive x-ray diffraction experiments up to 9 GPa were performed. Quasiharmonic lattice dynamics calculations are compared to the experimental results and show excellent agreement. The results are discussed with particular emphasis on the pressure dependence of the unit cell dimensions and the rearrangement of the molecules. The high pressure data also allow an analysis of the equation of state of these substances as a function of molecular length. We report the bulk modulus of tetracene and pentacene (B{sub 0}=9.0 and 9.6 GPa, respectively) and its pressure derivative (B{sub 0}{sup '}=7.9 and 6.4, respectively). We find that the unit-cell volume and bulk modulus at ambient pressure follow a linear relationship with the molecular length.

Oehzelt, M.; Aichholzer, A.; Resel, R.; Heimel, G.; Venuti, E.; Della Valle, R. G. [Institute of Solid State Physics, Graz University of Technology, Petersgasse 16, A-8010 Graz (Austria); School of Chemistry and Biochemistry, Georgia Institute of Technology, Atlanta, Georgia 30332-0400 (United States); Dipartimento di Chimica Fisica e Inorganica and INSTM-UdR Bologna, Universita di Bologna, Viale Risorgimento 4, I-40136 Bologna (Italy)

2006-09-01

265

Crystal structure of a snake venom cardiotoxin  

SciTech Connect

Cardiotoxin V/sup II/4 from Naja mossambica crystallizes in space group P6/sub 1/ (a = b = 73.9 A; c = 59.0 A) with two molecules of toxin (molecular mass = 6715 Da) in the asymmetric unit. The structure was solved by using a combination of multiple isomorphous replacement and density modification methods. Model building and least-squares refinement led to an agreement factor of 27% for a data set to 3-A resolution prior to any inclusion of solvent molecules. The topology of the molecule is similar to that found in short and long snake neurotoxins, which block the nicotinic acetylcholine receptor. Major differences occur in the conformation of the central loop, resulting in a change in the concavity of the molecule. Hydrophobic residues are clustered in two distinct areas. The existence of stable dimeric entities in the crystalline state, with the formation of a six-stranded antiparallel ..beta.. sheet, may be functionally relevant.

Rees, B.; Samama, J.P.; Thierry, J.C.; Gilibert, M.; Fischer, J.; Schweitz, H.; Lazdunski, M.; Moras, D.

1987-05-01

266

Tunable photonic structures from liquid crystal elastomers  

NASA Astrophysics Data System (ADS)

We investigated one-dimensional and two-dimensional optical diffraction structures fabricated in thin films of a sidechain light-sensitive liquid crystal elastomer (SC-LS-LCEs) by optical holographic lithography methods. The emphasis was on analysis of modifications of the periodicity of the recorded patterns induced by application of an external strain and by temperature modifications. The results show that due to rubber elasticity of the LCE films, relative modifications of the periodicity by 10% can easily be reached. In most cases tuning is reversible and linear with respect to the strain. Temperature induced tuning is most efficient in the region of phase transition from the nematic to the paranematic phase and provides relative periodicity modifications up to 30%.

Gregorc, Marko; Li, Hui; Domenici, Valentina; Drevenek-Olenik, Irena

2012-11-01

267

Cryogenic structural materials for superconducting magnets  

SciTech Connect

This paper reviews research in the United States and Japan on structural materials for high-field superconducting magnets. Superconducting magnets are used for magnetic fusion energy devices and for accelerators that are used in particle-physics research. The cryogenic structural materials that we review are used for magnet cases and support structures. We expect increased materials requirements in the future.

Dalder, E.N.C.; Morris, J.W. Jr.

1985-02-22

268

Structural and optical study on a single crystal of a novel fluorinated acridine  

NASA Astrophysics Data System (ADS)

Within a new class of anthracene-like molecules, namely tetrafluoro-acridines, a systematic study of the structural and optical properties of single crystals of a prototypical member, 1,2,3,4-tetrafluoro-7(N,N)dimethyl-amino-acridine, is illustrated. Single crystals were grown by physical vapour transport using an inert gas flow as carrier, starting from a microcrystalline powder of the pure material. The crystal structure, determined by X ray diffraction, points out that the crystals are monoclinic with molecules stacked along the c axis. The results of atomic force microscopy on the ac face of a single crystal, at both low and molecular resolution, are consistent with the X-ray diffraction data. Preliminary results of the optical properties of the single crystal, in the unique configuration accessible due to the peculiar habit of the samples, are discussed.

Miozzo, L.; Campione, M.; Moret, M.; Papagni, A.; Sassella, A.

2004-05-01

269

Synthesis, crystal growth and characterization of a chiral compound (triphenylphosphine oxide cadmium iodide): A new semiorganic nonlinear optical material  

NASA Astrophysics Data System (ADS)

Synthesis of semiorganic material, triphenylphosphine oxide cadmium iodide (TPPOCdI), is reported for the first time. Employing the temperature reduction method, a crystal of size 1676 mm 3 was grown from dimethyl sulfoxide (DMSO) solution. Three dimensional crystal structure of the grown crystal was determined by single crystal X-ray diffraction study. The complex crystallizes in the chiral orthorhombic space group P2 12 12 1. FTIR study was carried out in order to confirm the presence of the functional groups. UV-vis-NIR spectral studies show that the crystal is transparent in the wavelength range of 290-1100 nm. The microhardness test was carried out, and the load hardness was measured. Thermogravimetric and differential thermal analyses reveal the thermal stability of the crystal. Second harmonic generation efficiency of the powdered TPPOCdI, tested using Nd: YAG laser, is ?0.65 times that of potassium dihydrogen orthophosphate.

Santhakumari, R.; Ramamurthi, K.; Stoeckli-Evans, Helen; Hema, R.; Nirmala, W.

2011-05-01

270

Homochiral Crystallization of Microporous Framework Materials from Achiral Precursors by Chiral Catalysis  

PubMed Central

While it is not uncommon to form chiral crystals during crystallization, the formation of bulk porous homochiral materials from achiral building units is rare. Reported here is the homochiral crystallization of microporous materials through the chirality induction effect of natural alkaloids. The resulting material possesses permanent microporosity and has a uniform pore size of 9.3.

Zhang, Jian; Chen, Shumei; Wu, Tao; Feng, Pingyun; Bu, Xianhui

2009-01-01

271

Ab initio crystal structure prediction. II. Flexible molecules  

NASA Astrophysics Data System (ADS)

An extension of a recently reported algorithm (J. Comput. Chem., 26, 304 (2005)) for the prediction of the crystal structure of organic materials to molecules whose conformation is likely to be significantly affected by the packing forces is presented. The molecule is modelled as a set of rigid fragments connected by flexible torsion angles whose values in the crystalline environment are determined by the balance of intra- and inter-molecular forces. The intramolecular energy is initially computed using quantum mechanics over a grid in the space of flexible torsion angles. This allows the intramolecular energy to be expressed as a continuous and differentiable function of the torsion angles using multidimensional interpolants based on restricted cubic Hermite polynomials. The intermolecular electrostatic interactions are treated with a conformation-dependent atomic charge model, with the charges also being expressed as functions of the flexible torsion angles using restricted Hermite interpolants. Overall, this approach allows the computationally efficient, yet accurate, evaluation of the parts of the lattice enthalpy that depend on the molecular conformation. The proposed algorithm requires only the atomic connectivity of the molecule under consideration and performs an extensive search for local minima of the lattice enthalpy surface by using deterministic low-discrepancy sequences to ensure an optimal coverage of the search space. Candidate structures can be generated in the 59 most common space groups with one or more crystallographically independent entities. These are then used as starting points of local optimization calculations performed with a sequential quadratic programming algorithm, which makes use of analytical partial derivatives with respect to all inter and intra-molecular degrees of freedom. A parallelized implementation of the algorithm allows minimizations from several hundreds of thousands of initial guesses to be carried out in reasonable time. The algorithm is used to predict the crystal structures of the polymorphic system p-chlorobenzamide and to study the relative stability of the crystal structures of the diastereomeric salt pair (R)-1-phenylethylammonium, (R&S)-2-phenylbutyrate.

Karamertzanis, P. G.; Pantelides, C. C.

272

Ultrasmall-angle X-ray scattering analysis of photonic crystal structure  

SciTech Connect

The results of an ultrasmall-angle X-ray scattering study of iron(III) oxide inverse opal thin films are presented. The photonic crystals examined are shown to have fcc structure with amount of stacking faults varying among the samples. The method used in this study makes it possible to easily distinguish between samples with predominantly twinned fcc structure and nearly perfect fcc stacking. The difference observed between samples fabricated under identical conditions is attributed to random layer stacking in the self-assembled colloidal crystals used as templates for fabricating the inverse opals. The present method provides a versatile tool for analyzing photonic crystal structure in studies of inverse opals made of various materials, colloidal crystals, and three-dimensional photonic crystals of other types.

Abramova, V. V.; Sinitskii, A. S., E-mail: sinitsky@inorg.chem.msu.r [Moscow State University (Russian Federation); Grigor'eva, N. A. [St. Petersburg State University (Russian Federation); Grigor'ev, S. V. [Russian Academy of Sciences, Konstantinov St. Petersburg Nuclear Physics Institute (Russian Federation); Belov, D. V.; Petukhov, A. V. [Utrecht University, Debye Institute (Netherlands); Mistonov, A. A. [St. Petersburg State University (Russian Federation); Vasil'eva, A. V. [Russian Academy of Sciences, Konstantinov St. Petersburg Nuclear Physics Institute (Russian Federation); Tret'yakov, Yu. D. [Moscow State University (Russian Federation)

2009-07-15

273

Synthesis of rare-earth selenate and selenite materials under 'sol-gel' hydrothermal conditions: crystal structures and characterizations of La(HSeO{sub 3})(SeO{sub 4}) and KNd(SeO{sub 4}){sub 2}  

SciTech Connect

Two rare-earth compounds containing selenium atoms, La(HSeO{sub 3})(SeO{sub 4}) with a new open framework structure and KNd(SeO{sub 4}){sub 2} with a layered structure, have been synthesized under ''sol-gel'' hydrothermal conditions for the first time. Single-crystals of La(HSeO{sub 3})(SeO{sub 4}) crystallize in the monoclinic system (P2{sub 1}, a=8.5905(17)A, b=7.2459(14)A, c=9.5691(19)A, {beta}=104.91(3){sup o}, Z=2, RAll=0.032). The structure contains puckered polyhedral layers made of LaO{sub x} (x=9,10) and SeO{sub 4} groups, which are connected via SeO{sub 3}-uints to the 3D structure. The crytal structure of KNd(SeO{sub 4}){sub 2} (monoclinc, P2{sub 1}/c, a=8.7182(17)A, b=7.3225(15)A, c=11.045(2)A, {beta}=91.38(3){sup o}, Z=4, RAll=0.051) contains honeycomb-like six-ring NdO{sub 9} polyhedra forming layers which are further decorated with SeO{sub 4} tetrahedra. The K{sup +} ions occupy the interspaces of these layers and provide the charge balance.

Liu Wei [State Key Laboratory of High Performance Ceramics and Superfine Microstructure, Shanghai Institute of Ceramics, Chinese Academy of Science, Number 1295, Ding Xi Road, Shanghai, 200050 (China); Chen Haohong [State Key Laboratory of High Performance Ceramics and Superfine Microstructure, Shanghai Institute of Ceramics, Chinese Academy of Science, Number 1295, Ding Xi Road, Shanghai, 200050 (China); Yang Xinxin [State Key Laboratory of High Performance Ceramics and Superfine Microstructure, Shanghai Institute of Ceramics, Chinese Academy of Science, Number 1295, Ding Xi Road, Shanghai, 200050 (China); Li Mangrong [State Key Laboratory of High Performance Ceramics and Superfine Microstructure, Shanghai Institute of Ceramics, Chinese Academy of Science, Number 1295, Ding Xi Road, Shanghai, 200050 (China); Zhao Jingtai [State Key Laboratory of High Performance Ceramics and Superfine Microstructure, Shanghai Institute of Ceramics, Chinese Academy of Science, Number 1295, Ding Xi Road, Shanghai, 200050 (China)]. E-mail: jtzhao@mail.sic.ac.cn

2004-12-01

274

Study of the interfacial structures and behavior of smectic liquid crystals using synchrotron light source  

NASA Astrophysics Data System (ADS)

Grazing Incidence X-ray Scattering with a synchrotron X-ray source is used to study the depth dependence of the interfacial structure of smectic liquid crystal (8CB) hybrid films. The advancement and market potential of liquid crystal technologies lead to inventions of new materials and surface treatments. The knowledge of interfacial structures and behavior is very critical to these thin film devices such as Liquid Crystal Display. Photolithography in a clean room is adopted to make gratings on very thin glass, which offers better quality than conventional methods in terms of uniformity, reproducibility, reliability, and endurance. Liquid crystal thin films are bounded by a grated glass substrate and air, and have been studied as a function of both temperature and thickness. Experimental measurements indicate the existence of chevron, tilt, and bookshelf structure, as well as Twisted Grain Boundary (TGB) structure that has not previously been observed by X-ray in non-chiral smectic liquid crystals. These structures are a result of liquid crystal anchoring at two dissimilar competing confining surfaces, air-smectics and smectics-grating substrate. With deeper grating, smectic liquid crystals are more constrained in structure and more resilient to temperature change. The smectic phase also persisted at a higher temperature above the smectic-nematic transition point on a deeper grating substrate. When the thickness of liquid crystal samples is beyond a certain point, the smectic liquid crystal begins to form different layers. Chevron structures appear in most situations, which is consistent with previous research A TGB structure is not tamable in a thicker sample where liquid crystals tend to realign themselves in a more stable structure.

Hu, Yufei

2003-10-01

275

Radiation effects on structural materials  

SciTech Connect

This report discusses the following topics on the effect radiation has on thermonuclear reactor materials: Atomic Displacements; Microstructure Evolution; Materials Engineering, Mechanics, and Design; Research on Low-Activation Steels; and Research Motivated by Grant Support.

Ghoniem, N.M.

1991-06-28

276

Materials processing threshold report. 1: Semiconductor crystals for infrared detectors  

NASA Technical Reports Server (NTRS)

An extensive search was performed of the open literature pertaining to infrared detectors to determine what constitutes a good detector and in what way performance is limited by specific material properties. Interviews were conducted with a number of experts in the field to assess their perceptions of the state of the art and of the utility of zero-gravity processing. Based on this information base and on a review of NASA programs in crystal growth and infrared sensors, NASA program goals were reassessed and suggestions are presented as to possible joint and divergent efforts between NASA and DOD.

Sager, E. V.; Thompson, T. R.; Nagler, R. G.

1980-01-01

277

Use of Pom Pons to Illustrate Cubic Crystal Structures.  

ERIC Educational Resources Information Center

Describes a method that uses olefin pom pons to illustrate cubic crystal structure. Facilitates hands-on examination of different packing arrangements such as hexagonal close-packed and cubic close-packed structures. (JRH)

Cady, Susan G.

1997-01-01

278

In situ characterization of crystal growth and heat treatment in semiconductor materials  

NASA Astrophysics Data System (ADS)

In situ characterization methods are being developed at the Idaho National Laboratory that can be used to characterize the atomic lattice structure of materials used for semiconductor and scintillation detectors during the crystal growth and heat treatment processes, which have been shown to be critical for the development of optimized semiconductor and scintillation radiation detectors. Multiple methods for implanting positrons into the material have been developed and integrated with measurement techniques including Doppler broadening, coincidence Doppler broadening and positron lifetime measurement. The INL developed induced positron technique allows positron measurements to be performed at depth up to 10 cm inside crystal boules. Also, a portable measurement system suitable for field use has been developed that is suitable for assessing heat treatments at depths up to 1 cm inside a material in an industrial environment. Results of measurements that address the effects of composition and heatup/melting/cool down on material lattice structures are discussed along with plans for the in situ crystal studies.

Akers, Douglas W.; Drigert, Mark; Roybal, Lyle

2007-09-01

279

Liquid-crystal materials find a new order in biomedical applications  

Microsoft Academic Search

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

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

2007-01-01

280

Growth and crystal structure of the BeAl 6O 10 single crystals  

NASA Astrophysics Data System (ADS)

Unlike earlier published works we have established incongruent melting for the compound BeAl 6O 10 (BHA). The conditions of growing crystals from their own melt with a superstoichiometric excess of BeO, using the Czochralski method, have been determined. The nature of inclusions in grown BHA crystals is described. On the basis of X-ray crystal structure analysis and data of spectroscopic studies the symmetry and space group of BHA crystal structure have been refined, as well as uncertainties arising in their interpretation are discussed.

Alimpiev, A. I.; Merkulov, A. A.; Solntsev, V. P.; Tsvetkov, E. G.; Matrosov, V. N.; Pestryakov, E. V.

2002-04-01

281

A review of fine structures of nanoporous materials as evidenced by microscopic methods.  

PubMed

This paper reviews diverse capabilities offered by modern electron microscopy techniques in studying fine structures of nanoporous crystals such as zeolites, silica mesoporous crystals, metal organic frameworks and yolk-shell materials. For the case of silica mesoporous crystals, new approaches that have been developed recently to determine the three-dimensionally periodic average structure, e.g., through self-consistent analysis of electron microscope images or through consideration of accidental extinctions, are presented. Various structural deviations in nanoporous materials from their average structures including intergrowth, surface termination, incommensurate modulation, quasicrystal and defects are demonstrated. Ibidem observations of the scanning electron microscope and atomic force microscope give information about the zeolite-crystal-growth mechanism, and an energy for unstitching a building-unit from a crystal surface is directly observed by an anatomic force microscope. It is argued how these observations lead to a deeper understanding of the materials. PMID:23349242

Liu, Zheng; Fujita, Nobuhisa; Miyasaka, Keiichi; Han, Lu; Stevens, Sam M; Suga, Mitsuo; Asahina, Shunsuke; Slater, Ben; Xiao, Changhong; Sakamoto, Yasuhiro; Anderson, Michael W; Ryoo, Ryong; Terasaki, Osamu

2013-02-01

282

Crystal structure prediction could have helped the experimentalists with polymorphism in benzamide  

Microsoft Academic Search

Benzamide was the first molecular material for which polymorphism was reported, as long as 176 years ago. Unfortunately, due to very similar cell metrics leading to massive peak overlap, the metastable form reported by Liebig escaped structural characterisation by XRD until recently. With the help of crystal structure prediction this old riddle of Liebig's polymorph of benzamide could have been

Juergen Thun; Markus Schoeffel; Josef Breu

2008-01-01

283

Liquid crystal materials and tunable devices for optical communications  

NASA Astrophysics Data System (ADS)

In this dissertation, liquid crystal materials and devices are investigated in meeting the challenges for photonics and communications applications. The first part deals with polymer-stabilized liquid crystal (PSLC) materials and devices. Three polymer-stabilized liquid crystal systems are developed for optical communications. The second part reports the experimental investigation of a novel liquid-crystal-infiltrated photonic crystal fiber (PCF) and explores its applications in fiber-optic communications. The curing temperature is found to have significant effects on the PSLC performance. The electro-optic properties of nematic polymer network liquid crystal (PNLC) at different curing temperatures are investigated experimentally. At high curing temperature, a high contrast, low drive voltage, and small hysteresis PNLC is obtained as a result of the formed large LC microdomains. With the help of curing temperature effect, it is able to develop PNLC based optical devices with highly desirable performances for optical communications. Such high performance is generally considered difficult to realize for a PNLC. In fact, the poor performance of PNLC, especially at long wavelengths, has hindered it from practical applications for optical communications for a long time. Therefore, the optimal curing temperature effect discovered in this thesis would enable PSLCs for practical industrial applications. Further more, high birefringence LCs play an important role for near infrared photonic devices. The isothiocyanato tolane liquid crystals exhibit a high birefringence and low viscosity. The high birefringence LC dramatically improves the PSLC contrast ratio while keeping a low drive voltage and fast response time. A free-space optical device by PNLC is experimentally demonstrated and its properties characterized. Most LC devices are polarization sensitive. To overcome this drawback, we have investigated the polymer-stabilized cholesteric LC (PSCLC). Combining the curing temperature effect and high birefringence LC, a polarization independent fiber-optical device is realized with over 30 dB attenuation, 12 V rms drive voltage and 11/28 milliseconds (rise/decay) response times. A polymer-stabilized twisted nematic LC (PS TNLC) is also proposed as a variable optical attenuator for optical communications. By using the polarization control system, the device is polarization independent. The polymer network in a PS TNLC not only results in a fast response time (0.9/9 milliseconds for rise/decay respectively), but also removes the backflow effect of TNLC which occurs in the high voltage regime. Another major achievement in this thesis is the first demonstration of an electrically tunable LC-infiltrated photonic crystal fiber (PCF). Two different LC PCF configurations are studied. For the first time, electrically tunable LC PCFs are demonstrated experimentally. The guiding mechanism and polarization properties are studied. Preliminary experimental results are also given for the thermo-optical properties of a LC filled air-core PCF. In conclusion, this dissertation has solved important issues related to PSLC and enables its applications as VOAs and light shutters in optical communications. Through experimental investigations of the LC filled PCFs, a new possibility of developing tunable micro-sized fiber devices is opened for optical communications as well.

Du, Fang

284

Structural biological materials: critical mechanics-materials connections.  

PubMed

Spider silk is extraordinarily strong, mollusk shells and bone are tough, and porcupine quills and feathers resist buckling. How are these notable properties achieved? The building blocks of the materials listed above are primarily minerals and biopolymers, mostly in combination; the first weak in tension and the second weak in compression. The intricate and ingenious hierarchical structures are responsible for the outstanding performance of each material. Toughness is conferred by the presence of controlled interfacial features (friction, hydrogen bonds, chain straightening and stretching); buckling resistance can be achieved by filling a slender column with a lightweight foam. Here, we present and interpret selected examples of these and other biological materials. Structural bio-inspired materials design makes use of the biological structures by inserting synthetic materials and processes that augment the structures' capability while retaining their essential features. In this Review, we explain this idea through some unusual concepts. PMID:23413348

Meyers, Marc Andr; McKittrick, Joanna; Chen, Po-Yu

2013-02-15

285

Crystal structure of Cu2Te predicted within adaptive genetic algorithm  

NASA Astrophysics Data System (ADS)

Cu2Te is one of the most commonly used conductive back-contacting materials for high-efficiency CdTe-based solar cells. However, the detailed crystal structure of Cu2Te is still undetermined blocking property investigations of the Cu2Te-based solar cell systems. Some models have been proposed but all of them have positive formation energy [1]. We have performed adaptive genetic algorithm crystal structure search to find low energy crystal structures of Cu2Te. We found a new layered-structure edged by Te atoms with negative formation energy from first-principles calculations within local density approximation. This layered structure consists of tilted Cu2Te ribbon arrays. Structural and electronic properties of the newly found Cu2Te structure will be discussed in detail.[4pt] [1] J. L. F. Da Silva, S.-H. Wei, J. Zhou, and X. Wu, Appl. Phys. Lett. 91, 091902 (2007)

Ho, Kai-Ming; Nguyen, Manh Cuong; Choi, Jinho; Wang, Cai-Zhuang; Zhao, Xin; Zhang, Zhenyu

2013-03-01

286

Refinement of the crystal structure of rutherfordine.  

SciTech Connect

Rutherfordine, UO{sub 2}CO{sub 3} is orthorhombic, a 4.840(1), b 9.273(2), c 4.298(1) Angstroms, V192.90(7) Angstroms{sup 3}, space group lmm2,Z=2. The structure was refined to an R index of 2.2% on the basis of 306 unique data [|F{sub o}|/{sigma}(|F{sub o}|)>5] measured with MoK{alpha} X-radiation on a single-crystal diffractometer. The structure consists of neutral sheets of edge- and corner-sharing (UO{sub 8}) hexagonal bipyramids and (CO{sub 3}) triangles, as originally proposed by Christ et al. (1955); our refinement, however shows that (CO{sub 3}) groups in alternate layers have the same orientation, not opposite orientations as originally reported. The refined value of the U-O (uranyl) distance is strongly affected by the details of the absorption correction, ranging from 1.71 to 1.80 Angstroms as a function of the plate-glancing angle used in an empirical psi-scan absorption correction and as a function of the type of weighting scheme used in the refinement. The Gaussian-quadrature method of integration also shows similar problems, but they are less extreme. The preferred value for the U-O (uranyl) distance in rutherfordine is {approx}1.745 Angstroms; as rutherfordine contains no H atoms, the O(uranyl) atom is [1]-coordinated, and should have the shortest U-O(uranyl) distance stereochemically possible. The current work suggests that U-O(uranyl) values less than 1.745 Angstrom reported in other studies are adversely affected by less-than-optimum absorption corrections.

Finch, R. J.; Cooper, M. A.; Hawthorne, F. C.; Ewing, R. C.; Chemical Engineering; Univ. of Manitoba; Univ. of Michigan

1999-01-01

287

Crystal Structure of a "Nonfoldable" Insulin  

PubMed Central

Protein evolution is constrained by folding efficiency (foldability) and the implicit threat of toxic misfolding. A model is provided by proinsulin, whose misfolding is associated with ?-cell dysfunction and diabetes mellitus. An insulin analogue containing a subtle core substitution (LeuA16 ? Val) is biologically active, and its crystal structure recapitulates that of the wild-type protein. As a seeming paradox, however, ValA16 blocks both insulin chain combination and the in vitro refolding of proinsulin. Disulfide pairing in mammalian cell culture is likewise inefficient, leading to misfolding, endoplasmic reticular stress, and proteosome-mediated degradation. ValA16 destabilizes the native state and so presumably perturbs a partial fold that directs initial disulfide pairing. Substitutions elsewhere in the core similarly destabilize the native state but, unlike ValA16, preserve folding efficiency. We propose that LeuA16 stabilizes nonlocal interactions between nascent ?-helices in the A- and B-domains to facilitate initial pairing of CysA20 and CysB19, thus surmounting their wide separation in sequence. Although ValA16 is likely to destabilize this proto-core, its structural effects are mitigated once folding is achieved. Classical studies of insulin chain combination in vitro have illuminated the impact of off-pathway reactions on the efficiency of native disulfide pairing. The capability of a polypeptide sequence to fold within the endoplasmic reticulum may likewise be influenced by kinetic or thermodynamic partitioning among on- and off-pathway disulfide intermediates. The properties of [ValA16]insulin and [ValA16]proinsulin demonstrate that essential contributions of conserved residues to folding may be inapparent once the native state is achieved.

Liu, Ming; Wan, Zhu-li; Chu, Ying-Chi; Aladdin, Hassan; Klaproth, Birgit; Choquette, Meredith; Hua, Qing-xin; Mackin, Robert B.; Rao, J. Sunil; De Meyts, Pierre; Katsoyannis, Panayotis G.; Arvan, Peter; Weiss, Michael A.

2009-01-01

288

Recovery of valuable materials from waste liquid crystal display panel  

SciTech Connect

Associated with the rapid development of the information and electronic industry, liquid crystal displays (LCDs) have been increasingly sold as displays. However, during the discarding at their end-of-life stage, significant environmental hazards, impacts on health and a loss of resources may occur, if the scraps are not managed in an appropriate way. In order to improve the efficiency of the recovery of valuable materials from waste LCDs panel in an environmentally sound manner, this study presents a combined recycling technology process on the basis of manual dismantling and chemical treatment of LCDs. Three key processes of this technology have been studied, including the separation of LCD polarizing film by thermal shock method the removal of liquid crystals between the glass substrates by the ultrasonic cleaning, and the recovery of indium metal from glass by dissolution. The results show that valuable materials (e.g. indium) and harmful substances (e.g. liquid crystals) could be efficiently recovered or separated through above-mentioned combined technology. The optimal conditions are: (1) the peak temperature of thermal shock to separate polarizing film, ranges from 230 to 240 deg. C, where pyrolysis could be avoided; (2) the ultrasonic-assisted cleaning was most efficient at a frequency of 40 KHz (P = 40 W) and the exposure of the substrate to industrial detergents for 10 min; and (3) indium separation from glass in a mix of concentrated hydrochloric acid at 38% and nitric acid at 69% (HCl:HNO{sub 3}:H{sub 2}O = 45:5:50, volume ratio). The indium separation process was conducted with an exposure time of 30 min at a constant temperature of 60 deg. C.

Li Jinhui [Department of Environmental Science and Engineering, Tsinghua University (China); Sino-Italia Environmental Energy Building, Room 804, Haidian District, Beijing 100084 (China)], E-mail: jinhui@tsinghua.edu.cn; Gao Song; Duan Huabo; Liu Lili [Department of Environmental Science and Engineering, Tsinghua University (China)

2009-07-15

289

Anisotropic domain structure of KTiOPO{sub 4} crystals  

SciTech Connect

Highly anisotropic ferroelectric domain structure is observed in KTiOPO{sub 4} (KTP) crystals reversed by low electric field. The applied Miller--Weinreich model for sidewise motion of domain walls indicates that this anisotropy results from the peculiarities of KTP crystal lattice. The domain nuclei of dozen nanometer size, imaged by atomic force microscopy method, demonstrate regular hexagonal forms. The orientation of domain walls of the elementary nuclei coincides with the orientation of the facets of macroscopic KTP crystals. The observed strong domain elongation along one principal crystal axis allows us to improve tailoring of ferroelectric domain engineered structures for nonlinear optical converters. {copyright} 2001 American Institute of Physics.

Urenski, P.; Lesnykh, M.; Rosenwaks, Y.; Rosenman, G.; Molotskii, M.

2001-08-15

290

Synthesis, crystal structure and vibrational spectroscopy of a nonlinear optical crystal: L-arginine maleate dihydrate  

NASA Astrophysics Data System (ADS)

From the aqueous solution containing L-arginine and maleic acid (C 4H 4O 4), crystals of L-arginine maleate dihydrate were grown. The crystal structure was determined by single crystal X-ray diffraction. In the triclinic unit cell (space group P1), the molecule contains one L-arginine cation, one maleate anion and two water molecules. The crystal can be described as an inclusion complex from its layer structure. The basic unit in L-arginine layer is centrosymmetric and the maleate anions exist in coplanarity. Hydrogen bond plays a great role in the construction of the crystal and nonlinear optical properties. The crystal was characterized by infrared (IR) and Raman spectra. Thermogravimetric analysis (TGA) and differential thermal analysis (DTA) were used to study its thermal properties. Powder second harmonic generation (SHG) experiment was investigated to explore its NLO properties.

Sun, Z. H.; Yu, W. T.; Cheng, X. F.; Wang, X. Q.; Zhang, G. H.; Yu, G.; Fan, H. L.; Xu, D.

2008-02-01

291

Structural Integrity of Intelligent Materials and Structures.  

National Technical Information Service (NTIS)

This report focuses on the development of micromechanical algorithms for shape memory alloy composite materials. The composite cylinders assemblage algorithm was utilized to determine the effective thermomechanical properties of shape memory alloy composi...

B. J. Sullivan K. W. Buesking

1994-01-01

292

Crystal structures at high pressures and temperatures  

NASA Astrophysics Data System (ADS)

The diamond anvil cell (DAC) is a unique instrument that can generate pressures equivalent to those inside planetary interiors (pressures on the order of 1 million atmospheres) under sustained conditions. When combined with a bright source of collimated x-rays, the DAC can be used to probe the structure of materials in-situ at ultra-high pressures. An understanding of the high-pressure structure of materials is important in determining what types of processes may take place in the Earth at great depths. Motivated by previous studies showing that xenon becomes metallic at pressures above 1 megabar (100 GPa), we examined the stable structures and reactivity of xenon at pressures approaching that of the core-mantle boundary in the Earth. Our findings indicate the transformation of xenon from face-centered cubic (fcc) to hexagonal close-packed (hcp) structures is kinetically hindered at room temperature, with the equilibrium fcc--hcp phase boundary at 21 (+/-3) gigapascals, a pressure lower than was previously thought. Additionally, we find no tendency on the part of xenon to form a metal alloy with iron or platinum to at least 100 to 150 gigapascals, making it unlikely that the Earth's core serves as a reservoir for primordial xenon. Measurements of the compressibility of natural (Mg.75,Fe .25)2SiO4 gamma-spinel at pressures of the Earth's transition zone yield a pressure derivative of the bulk modulus K0 ' = 6.3 (+/-0.3). As gamma-spinel is considered to be a dominant mineral phase of the transition-zone of the Earth's mantle (400--670 km depth), the relatively high value of K0' for gamma-spinel may help explain the rapid increase with depth of seismic velocities through the transition zone. The thermodynamics, mechanisms and kinetics of pressure-induced amorphization are not well understood. We report here new studies indicating little or no entropy difference between the crystalline and glassy states of Ca(OH) 2 (portlandite). Additional work on the pressure-induced amorphization of AlPO4 (berlinite) shows that this material, which is a close analog to quartz, shows a rich behavior that is dependent upon the pressure, temperature, stress-state and time-scales of the experimental conditions.

Caldwell, Wendel Alexander

2000-10-01

293

Low melting point organic crystal structures by high-resolution neutron powder diffraction: The structure determination of acetaldehyde  

Microsoft Academic Search

High-resolution neutron powder diffraction is particularly suited for structure solution and refinement of low melting point organic crystals. Whereas materials that are gas or liquid at ambient temperature pose practical difficulties both in growing single crystals and also in preparing small-volume samples for X-ray studies that exhibit a good powder average, low-temperature sample preparation and data collection for neutron powder

R. M Ibberson

1997-01-01

294

Low melting point organic crystal structures by high-resolution neutron powder diffraction: The structure determination of acetaldehyde  

Microsoft Academic Search

High-resolution neutron powder diffraction is particularly suited for structure solution and refinement of low melting point organic crystals. Whereas materials that are gas or liquid at ambient temperature pose practical difficulties both in growing single crystals and also in preparing small-volume samples for X-ray studies that exhibit a good powder average, low-temperature sample preparation and data collection for neutron powder

R. M. Ibberson

1998-01-01

295

Structural material irradiations in FFTF  

SciTech Connect

Information is presented concerning the Materials Open Test Assembly (MOTA); instrumentation and control system; MOTA neutronic data; pressurized tube specimens; stress-rupture measurements for reactor materials; miniature specimen design; the Interim Examination and Maintenance (IEM) cell at the FFTF; support services; and general information concerning the FFTF.

Not Available

1985-01-01

296

Material Selection for Cryogenic Support Structures  

NASA Astrophysics Data System (ADS)

Design specifications for the support structures of low temperature instrumentation often call for low thermal conductivity between temperature stages, high stiffness, and specific load bearing capabilities. While overall geometric design plays an important role in both overall stiffness and heat conduction between stages, material selection can affect a structure's properties significantly. In this contribution, we suggest and compare several alternative materials to the current standard materials for building cryogenic support structures.

Kramer, Erik; Kellaris, Nicholas; Daal, Miguel; Sadoulet, Bernard; Golwala, Sunil; Hollister, Matthew

2014-01-01

297

Effective second-order susceptibility in photonic crystals mode of centrosymmetric materials  

NASA Astrophysics Data System (ADS)

A technique for obtaining efficient bulk second-order susceptibility in noncentrosymmetric photonic crystals (PC) made of centrosymmetric materials is discussed. The effect is based on the electric quadrupole effect, strong electromagnetic mode deformation, and nonhomogeneous contribution to volume polarization from different parts of the PC. The required symmetry breaking is introduced on the macroscale of the PC unit cell. The obtained structural ?(2)str is comparable with the second-order susceptibility of ordinary nonlinear materials. Phase matching can be achieved by introducing symmetry modulation (quasi-phase-matching) during fabrication of the PC.

Feigel, A.; Kotler, Z.; Sfez, B.

2002-02-01

298

Synthesis, characterization, and crystal structures of novel single and mixed-metal framework materials assembled from 2-(4-pyridyl)thiazole-4-carboxylic acid with cobalt, cadmium, and vanadium oxide  

NASA Astrophysics Data System (ADS)

Three new coordination polymers containing 2-(4-pyridyl)thiazole-4-carboxylate (pytac) with cobalt, vanadium oxide, or cadmium iodide have been synthesized solvothermally, isolated, and characterized by single-crystal X-ray diffraction and powder X-ray diffraction. [Co 3(pytac) 6](H 2O) 8 ( 1), which crystallizes in the space group C2/ c ( a = 24.1418(8) , b = 17.5088(6) , and c = 14.4562(5) , ? = 96.0390(10)), has 1D hexameric water channels that constitute a 14.4% of the unit cell volume. Co 3(pytac) 2(H 2O) 4V 4O 12 ( 2), which crystallizes in the space group P1 ( a = 8.6591(5) , b = 9.0044(5) , and c = 10.6495(6) , ? = 67.1160(10), ? = 82.6880(10), and ? = 83.9880(10)), is an extension of the former in that it contains Co(H 2O) 4V 4O 12 in addition to the Co-only 2D layers. [CdI(pytac)(H 2O)]H 2O ( 3), which also crystallizes in the space group P1 ( a = 8.2376(4) , b = 8.4859(4) , and c = 11.1261(5) , ? = 68.2020(10), ? = 77.5610(10), and ? = 69.1230(10)), exhibits structural characteristics similar to 2, in that both contain 1D chains where the pytac ligand simultaneously engages in three different coordination modes: chelating, single bond coordination, and ?-2 bridging between two metal centers via carboxylate oxygen atoms.

Ellsworth, Joseph M.; Khaliq, Zeeshan M.; Smith, Mark D.; zur Loye, Hans-Conrad

2008-07-01

299

The solution structure of liquid-crystal polymers with small liquid-crystal thermoset maleimides and nadimides  

SciTech Connect

The solution structure of the deuterated liquid-crystal polyamide polymer (LCP) poly(p-phenylene-2-nitroterephthalamide), alone and mixed with small, rodlike, amide, liquid-crystal molecules (LCT) in N-methyl-2-pyrrolidinone (NMP), is studied using small-angle neutron scattering. Measurements were made as a function of LCP concentration using different LCTs mixed at 20 and 40 wt% relative to LCP. Our motivation for studying this system comes from a need to connect solution structure with film morphology in processing these materials for high-performance molecular composites. Our analysis shows that LCP in NMP forms large domain-like structures. The presence of LCT breaks up the LCP domains into smaller structures, some of which are filamentous LCP-LCT aggregates. This result suggests that the simple entropic description of the solution behavior of mixtures of long and short rods is not adequate in describing systems of this type.

Hjelm, R.P.; Douglas, E.P.; Benicewicz, B.C. [Los Alamos National Lab., NM (United States)

1995-03-01

300

Evolutionary Crystal Structure Prediction and Novel High-Pressure Phases  

Microsoft Academic Search

\\u000a Prediction of stable crystal structures at given pressure-temperature conditions, based only on the knowledge of the chemical\\u000a composition, is a central problem of condensed matter physics. This extremely challenging problem is often termed crystal\\u000a structure prediction problem, and recently developed evolutionary algorithm USPEX (Universal Structure Predictor: Evolutionary\\u000a Xtallography) made an important progress in solving it, enabling efficient and reliable prediction

Artem R. Oganov; Yanming Ma; Andriy O. Lyakhov; Mario Valle; Carlo Gatti

2010-01-01

301

Structural study of Langmuir liquid crystal monolayer  

NASA Astrophysics Data System (ADS)

A systematic study is reported on monolayer characteristics of Ferroelectric Liquid Crystal (FLC) at the air-water interface, using surface pressure and surface potential isotherms at different temperatures. Dipole moment is calculated by using Helmholtz equation. No significant influence from the sub phase temperature was detected because liquid crystal remains in Sm-C* phase in temperature range 5C-40C. FLC was deposited on smooth quartz substrate with good transfer ratio. AFM topography reveals uniform deposition of liquid crystals having well defined domains.

Kaur, Ramneek; Raina, K. K.

2014-04-01

302

Novel photonic crystal cavities and related structures.  

SciTech Connect

The key accomplishment of this project is to achieve a much more in-depth understanding of the thermal emission physics of metallic photonic crystal through theoretical modeling and experimental measurements. An improved transfer matrix technique was developed to enable incorporation of complex dielectric function. Together with microscopic theory describing emitter radiative and non-radiative relaxation dynamics, a non-equilibrium thermal emission model is developed. Finally, experimental methodology was developed to measure absolute emissivity of photonic crystal at high temperatures with accuracy of +/-2%. Accurate emissivity measurements allow us to validate the procedure to treat the effect of the photonic crystal substrate.

Luk, Ting Shan

2007-11-01

303

The crystal polymorphism of calcium carbonate is determined by the matrix structure in quail eggs.  

PubMed

Two calcified structures, the eggshell and sperm-associated body (SB), are present in the eggs of the Japanese quail, Coturnix japonica. X-ray diffractometry showed that calcium carbonates take the form of calcite in the eggshell and aragonite in the SB. The aim of the present study was to identify the factors that determine the morphology of calcium carbonate crystals. The matrix of EDTA-treated eggshell was a meshwork of vesicles, 200 to 500 nm in diameter, connected by fine fibers or fibrous sheets. The matrix of SB cortex was a radiation of rod-shaped projections approximately 130 nm in width. In vitro crystal formation was achieved by adding dissociated matrix substances to test solutions. When eggshell matrix material was added, formation of calcite crystals, which had many vesicular holes on their surface, was observed. When SB matrix material dissociated by sonication was added, rhombohedral calcite crystals formed at protein concentrations of 100 microg/mL or lower, and elongated and bundled crystals formed at concentrations of 150 microg/mL or higher. When SB matrix material dissociated by pipetting was added, aragonite crystals formed. These observations indicate that the matrix structure is the principal factor in determining the crystal polymorphism of calcium carbonate. PMID:19903967

Iwasawa, A; Uzawa, M; Rahman, M A; Ohya, Y; Yoshizaki, N

2009-12-01

304

In vivo protein crystallization opens new routes in structural biology  

PubMed Central

Protein crystallization in cells has been observed several times in nature. However, owing to their small size these crystals have not yet been used for X-ray crystallographic analysis. We prepared nano-sized in vivogrown crystals of Trypanosoma brucei enzymes and applied the emerging method of free-electron laser-based serial femtosecond crystallography to record interpretable diffraction data. This combined approach will open new opportunities in structural systems biology.

Koopmann, Rudolf; Cupelli, Karolina; Redecke, Lars; Nass, Karol; DePonte, Daniel P; White, Thomas A; Stellato, Francesco; Rehders, Dirk; Liang, Mengning; Andreasson, Jakob; Aquila, Andrew; Bajt, Sasa; Barthelmess, Miriam; Barty, Anton; Bogan, Michael J; Bostedt, Christoph; Boutet, Sebastien; Bozek, John D; Caleman, Carl; Coppola, Nicola; Davidsson, Jan; Doak, R Bruce; Ekeberg, Tomas; Epp, Sascha W; Erk, Benjamin; Fleckenstein, Holger; Foucar, Lutz; Graafsma, Heinz; Gumprecht, Lars; Hajdu, Janos; Hampton, Christina Y; Hartmann, Andreas; Hartmann, Robert; Hauser, Gunter; Hirsemann, Helmut; Holl, Peter; Hunter, Mark S; Kassemeyer, Stephan; Kirian, Richard A; Lomb, Lukas; Maia, Filipe R N C; Kimmel, Nils; Martin, Andrew V; Messerschmidt, Marc; Reich, Christian; Rolles, Daniel; Rudek, Benedikt; Rudenko, Artem; Schlichting, Ilme; Schulz, Joachim; Seibert, M Marvin; Shoeman, Robert L; Sierra, Raymond G; Soltau, Heike; Stern, Stephan; Struder, Lothar; Timneanu, Nicusor; Ullrich, Joachim; Wang, Xiaoyu; Weidenspointner, Georg; Weierstall, Uwe; Williams, Garth J; Wunderer, Cornelia B; Fromme, Petra; Spence, John C H; Stehle, Thilo; Chapman, Henry N; Betzel, Christian; Duszenko, Michael

2012-01-01

305

Crystal and magnetic structure of the uranium digermanide UGe 2  

Microsoft Academic Search

The crystal structure of the uranium digermanide UGe2 was determined and refined from single crystal X-ray diffraction data to R = 0.040, Rw = 0.052. UGe2 crystallizes with the orthorhombic ZrGa2 type (Cmcm) instead of the ZrSi2 type (Cmcm) as was previously assumed on the basis of rather old and unreliable results. Our magnetic study of a polycrystalline are melted

P. Boulet; A. Daoudi; M. Potel; H. Nol; G. M. Gross; G. Andr; F. Boure

1997-01-01

306

Oxide Thermoelectric Materials: A Structure-Property Relationship  

NASA Astrophysics Data System (ADS)

Recent demand for thermoelectric materials for power harvesting from automobile and industrial waste heat requires oxide materials because of their potential advantages over intermetallic alloys in terms of chemical and thermal stability at high temperatures. Achievement of thermoelectric figure of merit equivalent to unity ( ZT ? 1) for transition-metal oxides necessitates a second look at the fundamental theory on the basis of the structure-property relationship giving rise to electron correlation accompanied by spin fluctuation. Promising transition-metal oxides based on wide-bandgap semiconductors, perovskite and layered oxides have been studied as potential candidate n- and p-type materials. This paper reviews the correlation between the crystal structure and thermoelectric properties of transition-metal oxides. The crystal-site-dependent electronic configuration and spin degeneracy to control the thermopower and electron-phonon interaction leading to polaron hopping to control electrical conductivity is discussed. Crystal structure tailoring leading to phonon scattering at interfaces and nanograin domains to achieve low thermal conductivity is also highlighted.

Nag, Abanti; Shubha, V.

2014-04-01

307

Structural Relaxation In Amorphous Materials  

Microsoft Academic Search

\\u000a In the glass transition region the molecular rearrangements slow down considerably. Then the macroscopic properties of the\\u000a amorphous material changes on a scale of minutes and they can easily be observed. If a such material is equilibrated at temperature\\u000a T\\u000a \\u000a o\\u000a in the glass transition region and then suddenly cooled to temperature T, the volume will change as shown in

J. Mllek; J. Shn?lov

308

Crystal structure of interleukin 8: Symbiosis of NMR and crystallography  

Microsoft Academic Search

The crystal structure of a host defense system chemotactic factor, interleukin 8, has been solved by molecular replacement using as a model the solution structure derived from nuclear magnetic resonance experiments. The structure was refined with 2 x-ray data to an R factor of 0.817. A comparison indicates some potential differences between the structure in solution and in the

E. T. Baldwin; I. T. Weber; R. St. Charles; Jiancheng Xuan; Kouji Matsushima; A. Wlodawer; E. Appella; G. M. Clore; A. M. Gronenborn; Masaki Yamada; B. F. P. Edwards

1991-01-01

309

Crystal Growth of Chiral Magnetic Material in CsCuCl3  

NASA Astrophysics Data System (ADS)

We report a crystallization technique to make single crystals with homochiral crystallographic domain in CsCuCl3. By adapting crystallization technique with stirring, we succeeded in obtaining the mm-ordered enantiopure single crystals. The samples obtained without the stirring crystallization technique had zigzag shape, suggesting many crystalline nuclei combined during the crystallization process. The samples done with the stirring crystallization technique formed quart-crystal-like shape, suggesting only one crystalline nucleus grew. Absolute structure analysis using X-ray diffraction showed that the samples grown only by our technique had a homochiral crystalline domain.

Kousaka, Yusuke; Koyama, Takemi; Miyagawa, Marina; Tanaka, Kohei; Akimitsu, Jun; Inoue, Katsuya

2014-04-01

310

Structural integrity of intelligent materials and structures  

NASA Astrophysics Data System (ADS)

This report focuses on the development of micromechanical algorithms for shape memory alloy composite materials. The composite cylinders assemblage algorithm was utilized to determine the effective thermomechanical properties of shape memory alloy composites. The mathematical development based on this micromechanical model was coded and exercised to predict the response of shape memory alloy fiber/elastomer matrix composites to arbitrary mechanical and thermal loadings.

Sullivan, Brian J.; Buesking, Kent W.

1994-02-01

311

III-Nitride LEDs with photonic crystal structures.  

SciTech Connect

Electrical operation of III-Nitride light emitting diodes (LEDs) with photonic crystal structures is demonstrated. Employing photonic crystal structures in III-Nitride LEDs is a method to increase light extraction efficiency and directionality. The photonic crystal is a triangular lattice formed by dry etching into the III-Nitride LED. A range of lattice constants is considered (a {approx} 270-340nm). The III-Nitride LED layers include a tunnel junction providing good lateral current spreading without a semi-absorbing metal current spreader as is typically done in conventional III-Nitride LEDs. These photonic crystal III-Nitride LED structures are unique because they allow for carrier recombination and light generation proximal to the photonic crystal (light extraction area) yet displaced from the absorbing metal contact. The photonic crystal Bragg scatters what would have otherwise been guided modes out of the LED, increasing the extraction efficiency. The far-field light radiation patterns are heavily modified compared to the typical III-Nitride LED's Lambertian output. The photonic crystal affects the light propagation out of the LED surface, and the radiation pattern changes with lattice size. LEDs with photonic crystals are compared to similar III-Nitride LEDs without the photonic crystal in terms of extraction, directionality, and emission spectra.

Wendt, Joel Robert; Sigalas, M. M. (Agilent Technologies, Palo Alto, CA); Epler, J. E. (Lumileds Lighting, San Jose, CA); Krames, M. R. (Lumileds Lighting, San Jose, CA); Li, D. (University of New Mexico, Albuquerque NM); Brueck, Stephen R. J. (University of New Mexico, Albuquerque NM); Shagam, M. (Boston University, Boston, MA); Gardner, N. F. (Lumileds Lighting, San Jose, CA); Wierer, Jonathan J. (Lumileds Lighting, San Jose, CA)

2005-02-01

312

III-nitride LEDs with photonic crystal structures  

NASA Astrophysics Data System (ADS)

Electrical operation of III-Nitride light emitting diodes (LEDs) with photonic crystal structures is demonstrated. Employing photonic crystal structures in III-Nitride LEDs is a method to increase light extraction efficiency and directionality. The photonic crystal is a triangular lattice formed by dry etching into the III-Nitride LED. A range of lattice constants is considered (a ~ 270 - 340nm). The III-Nitride LED layers include a tunnel junction providing good lateral current spreading without a semi-absorbing metal current spreader as is typically done in conventional III-Nitride LEDs. These photonic crystal III-Nitride LED structures are unique because they allow for carrier recombination and light generation proximal to the photonic crystal (light extraction area) yet displaced from the absorbing metal contact. The photonic crystal Bragg scatters what would have otherwise been guided modes out of the LED, increasing the extraction efficiency. The far-field light radiation patterns are heavily modified compared to the typical III-Nitride LED"s Lambertian output. The photonic crystal affects the light propagation out of the LED surface, and the radiation pattern changes with lattice size. LEDs with photonic crystals are compared to similar III-Nitride LEDs without the photonic crystal in terms of extraction, directionality, and emission spectra.

Wierer, Jonathan J.; Krames, Michael R.; Epler, John E.; Gardner, Nathan F.; Wendt, Joel R.; Sigalas, Mihail M.; Brueck, Steven R. J.; Li, Dong; Shagam, Michael

2005-03-01

313

Hydrothermal synthesis, crystal structure, and magnetic property of a three-dimensional inorganic-organic hybrid material: Mn(H 2O)[HO 3PCH 2NH(CH 2CO 2) 2  

NASA Astrophysics Data System (ADS)

A novel three-dimensional inorganic-organic hybrid compound, Mn(H 2O)[HO 3PCH 2NH(CH 2CO 2) 2] from a hydrothermal reaction of Mn (II) ion with N-(phosphonomethyl)iminodiacetic acid (H 4PMIDA) was reported. The compound crystallizes in the monoclinic P2 1/ n with cell dimensions of a=5.215(5) , b=14.111(15) , c=12.727(12) , ?=93.646(16), V=934.6(16) 3 and Z=4. In this structure each Mn atom is six-coordinated with the carboxylic groups and phosphonic groups to form layers along the bc plane. These layers are further connected with the organic moieties of H 2PMIDA, resulting in a complicated three-dimensional network structure. Thermogravimetric analysis, IR spectrum and magnetic susceptibility of this compound are given.

Fan, Yong; Li, Guanghua; Shi, Zhan; Zhang, Dong; Xu, Jianing; Song, Tianyou; Feng, Shouhua

2004-11-01

314

Crystal structure and characterization of pyrroloquinoline quinone disodium trihydrate  

PubMed Central

Background Pyrroloquinoline quinone (PQQ), a tricarboxylic acid, has attracted attention as a growth factor, and its application to supplements and cosmetics is underway. The product used for these purposes is a water-soluble salt of PQQ disodium. Although in the past, PQQ disodiumpentahydrates with a high water concentration were used, currently, low hydration crystals of PQQ disodiumpentahydrates are preferred. Results We prepared a crystal of PQQ disodium trihydrate in a solution of ethanol and water, studied its structure, and analyzed its properties. In the prepared crystal, the sodium atom interacted with the oxygen atom of two carboxylic acids as well as two quinones of the PQQ disodium trihydrate. In addition, the hydration water of the prepared crystal was less than that of the conventional PQQ disodium crystal. From the results of this study, it was found that the color and the near-infrared (NIR) spectrum of the prepared crystal changed depending on the water content in the dried samples. Conclusions The water content in the dried samples was restored to that in the trihydrate crystal by placing the samples in a humid environment. In addition, the results of X-ray diffraction (XRD) and X-ray diffraction-differential calorimetry (XRD-DSC) analyses show that the phase of the trihydrate crystal changed when the crystallization water was eliminated. The dried crystal has two crystalline forms that are restored to the original trihydrate crystals in 20% relative humidity (RH). This crystalline (PQQ disodium trihydrate) is stable under normal environment.

2012-01-01

315

Characterization of crystal structure in binary mixtures of latex globules.  

PubMed

Colloidal crystals formed by two types of polystyrene particles of different sizes (94 and 141 nm) at various number ratios (94:141 nm) are studied. Experiments showed that the formation time of crystals lengthens as the number ratio of the two components approaches 1:1. The dependence of the mean interparticle distance (D(0)), crystal structure and alloy structure on the number ratio of the two types of particles was studied by means of Kossel diffraction technique and reflection spectra. The results showed that as the number ratio decreased, the mean interparticle distance (D(0)) became larger. And the colloidal crystal in binary mixtures is more preferably to form the bcc structure. This study found that binary systems form the substitutional solid solution (sss)-type alloy structure in all cases except when the number ratio of two types of particles is 5:1, which results instead in the superlattice structure. PMID:18674779

Liu, Lei; Xu, Shenghua; Liu, Jie; Sun, Zhiwei

2008-10-01

316

New alkali metal diphosphates how materials to preserve the security of the environment: CsNaCu(P2O7), Rb2Cu(P2O7) and CsNaCo(P2O7) synthesis and crystal structure determination  

NASA Astrophysics Data System (ADS)

In this work we describe preliminary results of the synthesis and of a crystal-chemical study of synthetic phosphates with transition metals. Due to the increasing requirements for environmental safety specialists from various industries, we are searching for sustainable forms of immobilization of hazardous waste during storage. We are also developing a component-based waste for new materials. In our continued exploratory synthesis of compounds containing transition-metals, we were able to produce the new diphosphate phases CsNaCu(P2O7), Rb2Cu(P2O7) and CsNaCo(P2O7). A crystal chemical study has allowed us to identify new phosphates. Crystals of CsNaCu(P2O7) (Phase 1) is orthorhombic, crystallizes in space group Pmn21, with a = 5.147(8), b = 15.126(2), c = 9.717(2) , V = 756.20 3, R1 = 0.066 and Rb2Cu(P2O7) (Phase 2) is orthorhombic as well, crystallizes in space group Pmcn, with a = 5.183(8), b = 10.096(1), c = 15.146(3) , V = 793.55 3, R1 = 0.063, they have been obtained by high-temperature reaction of RbNO3, CsNO3, Cu(NO3)2, NaOH and (NH4)4P2O7. Synthetic crystals of the phosphate of copper and rubidium were studied in detail by us on the structures of Rb2Cu(P2O7) and Rb2Cu3(P2O7)2 - new alkali metal copper diphosphates (CHERNYATIEVA et al., 2008). Here we report the synthesis, the structure and the properties of the title compounds and we compare these phases with the previously discovered K2CuP2O7 (ELMAADI et al., 1995) and CsNaMnP2O7 (HUANG et al., 1998). These structures crystallize in other space groups, although their structures are also based on 2-D layers, formed by P2O7 groups combined with polyhedra of the transition metals (CHERNYATIEVA et al., 2012). A crystal chemical study has allowed us to identify even new diphosphates CsNaCu(P2O7) (Phase 3). Crystals of CsNaCoP2O7 is monoclinic, space group P 21/n, with a = 7,424(2), b = 7,648(1), c = 12,931(3), ? = 90,71(2) , V = 734.2(3) 3 and R1 = 0.060. The structure is based framework of Co tetrahedra and P2O7 groups. The structure of the [Co(P2O7)]2-framework in more detail. The phosphate groups and tetrahedra coordinate cobalt ions form topology. This is a unique 4-coordination topology, where Co and P2O7 groups in the structure are topologically equivalent. References CHERNYATIEVA, A. P., KRIVOVICHEV, S. V., SPIRIDONOVA, D. V. (2008): International conference Inorganic Materials Dresden (2008) P3 - 143. CHERNYATIEVA, A. P, SPIRIDONOVA, D. V., KRIVOVICHEV, S. V. The crystal structures of two new synthetic compounds CsNaCu(P2O7) and Rb2Cu(P2O7), Acta Mineralogica-Petrographica (2012) Vol.7, p.25 EL MAADI, A., BOUKHARI, A., HOLT, E.M. (1995) Journal of Alloys Compounds, 223: 13-17. HUANG, Q., HWU, S. J., MO, X. H. (2001): Angewandte Chemie - International Edition, 40: 1690-1693.

Chernyatieva, Anastasiya; Filatova, Alyona; Spiridonova, Dariya; Krivovichev, Sergey

2013-04-01

317

Three-Dimensional Visualization of Ice Crystals in Frozen Materials by Near-Infrared Imaging Spectroscopy  

NASA Astrophysics Data System (ADS)

Micro Slicer Spectral Imaging System (MSSIS) has been applied to observe the three-dimensional(3-D) structure and distribution of ice crystals formed in biological materials. MSSIS is composed of a micro-slicer, near-infrared (NIR) illuminator and spectral imaging system. NIR Spectroscopic analysis using MSSIS confirmed that there are a water absorption band around 965 nm and an ice absorption band around 1025 nm. Spectroscopic images of a frozen agar gel and a piece of raw beef at 1,025 nm were obtained by the MSSIS. These images showed the ice crystals could be clearly distinguished from the other components by the different absorbance. The average area of ice crystals was 6,253 ?m2, and the average distances of major and minor axis were 111?m and 62?m respectively. In addition, the 3-D re-constructed image of the ice crystal morphology revealed that they were formed along with the direction of heat transfer. The proposed method provided a novel tool to investigate the effects of freezing conditions on the size, morphology and distribution of ice crystals.

Do, Gab-Soo; Ueno, Shigeaki; Sagara, Yasuyuki; Tsuta, Mizuki; Sugiyama, Junichi

318

Growth and Structure of Single-Crystal Films.  

National Technical Information Service (NTIS)

This research project was concerned with basic research on the growth and structure of single-crystal films of metals obtained by evaporation in ultra-high vaccum onto two types of substrates: mica and metal single-crystal films. The films were prepared i...

E. Grunbaum

1968-01-01

319

The importance of crystal structure to the water treatment industry  

SciTech Connect

The intention of this paper is to provide additional insights into the area of crystal structure, dispersion and crystal modification, particularly for the calcium salts of carbonate and sulphate. The application of the discussed approaches to real life systems will go a long way to ensure scale-free heat transfer equipment.

Caplan, G.

1986-01-01

320

Electronic structure of Cr{sup 3+} in forsterite crystals  

SciTech Connect

Specific properties of silicate crystals that make them promising in applications as active media for IR tunable lasers are discussed. The energy level structure of Cr{sup 3+} ions in a forsterite crystal field is analyzed. 4 refs., 3 tabs.

Avanesov, A.G.; Zhorin, V.V.; Pisarenko, V.F. [Kuban` State Univ., Krasnodar (Russian Federation)

1994-11-01

321

Preparation of rare earth materials, crystals and specimens  

NASA Astrophysics Data System (ADS)

The reactive nature of rare earth metals is frequently noted but is usually only a problem during the preparative stages. In terms of processing of rare earth metals the dominant feature is their reactivity: vapour pressure and phase transformations are two other parameters that have a major influence. We present our state-of-art position in the preparation of specimens of rare earth materials. Production to a given materials requirement can involve various processes including refining, alloying and crystal growth, where the basic requirement is the use of a non-contaminating environment, e.g. ultra high vacuum. We have extended our refining studies to include vacuum re-melting, sublimation, zone-refining and solid state electrotransport. Considerable technical developments have also been achieved and our latest equipment includes, for instance, the capability of RF vertical float zoning in UHV and pressurised melt-growth. Following the processing stages we are concerned with actual specimen fabrication and report recent developments to improve surface preparation, particularly to deal with brittle materials.

Jones, D. W.; Abell, J. S.; Fort, D.; Hulbert, J. K.

1982-10-01

322

Coherent anti-Stokes Raman scattering polarized microscopy of three-dimensional director structures in liquid crystals  

NASA Astrophysics Data System (ADS)

We demonstrate three-dimensional vibrational imaging of director structures in liquid crystals using coherent anti-Stokes Raman scattering (CARS) polarized microscopy. Spatial mapping of the structures is based on sensitivity of a polarized CARS signal to the orientation of anisotropic molecules in liquid crystals. As an example, we study structures in a smectic material and demonstrate that single-scan CARS and two-photon fluorescence images of molecular orientation patterns are consistent with each other and with the structure model.

Kachynski, A. V.; Kuzmin, A. N.; Prasad, P. N.; Smalyukh, I. I.

2007-10-01

323

Local structure study of new thermoelectric materials  

Microsoft Academic Search

The atomic pair distribution function (PDF) technique is used to study the local structure of new thermoelectric materials. The PDF is obtained via Fourier transformation of powder total scattering data including the important local structural information in the diffuse scattering intensities underneath, and in-between, the Bragg peaks. Having long been used to study liquids and amorphous materials, the PDF technique

He Lin

2006-01-01

324

Materials and structures/ACEE  

NASA Technical Reports Server (NTRS)

Light weight composites made from graphite fibers, glass, or man made materials held in an epoxy matrix, and their application to airframe design are reviewed. The Aircraft Energy Efficiency program is discussed. Characteristics of composites, acceptable risks, building parts and confidence, and aeroelastic tailoring are considered.

1981-01-01

325

Prediction of Phase Diagrams for Hard Materials: Application to Boron Crystals  

NASA Astrophysics Data System (ADS)

Hard materials and refractory materials, such as diamond, are generally stable and have high melting points. The phase diagrams of these materials seem to be relatively simple. However, recent progress of high-pressure experiments along with theoretical predictions by density-functional theoretical (DFT) methods has disclosed the richness of new structures, which has attracted the attention of material researchers. An elemental crystal of boron is an extreme case; there are many polymorphic modifications, and it is only recently that the phase diagram has been established. In the course of studying the phase diagram, a new structure of the ?-phase has been discovered. Now, we have to admit that hard materials are rich sources for materials research. Many metastable phases are hidden behind the widely accepted phase diagrams. How to discover these hidden phases is one of the central issues for materials research. In this paper, experiences with predicting the phase diagram of boron by a theoretical approach are described and impacts on materials research, by taking superconductivity research as a working example, are shown. A combination of the microscopic method of DFT and the macroscopic approach of thermodynamics is an extremely powerful tool.

Shirai, Koun

2013-06-01

326

Sapphire: Relation between luminescence of starting materials and luminescence of single crystals  

NASA Astrophysics Data System (ADS)

A relation between photoluminescence (PL) characteristics of different starting materials used for crystal growth and un-doped sapphire single crystals manufactured using various methods of crystal growth (Kyropolus, HEM, Czochralski, and EFG) was found. The crystals grown using the Verneuil starting material exhibited significant PL when any method of crystal growth was used. On the contrary, sapphire samples grown by the same technologies wherein the starting material was EMT HPDA R revealed very low PL. (HPDA R is produced by EMT, Inc., with proprietary and patented technology.)

Mogilevsky, R.; Nedilko, S.; Sharafutdinova, L.; Burlay, S.; Sherbatskii, V.; Boyko, V.; Mittl, S.

2009-10-01

327

Framework-Type Determination for Zeolite Structures in the Inorganic Crystal Structure Database  

NASA Astrophysics Data System (ADS)

In this work a structural characterization of zeolite crystals is performed by identifying the framework type to which each zeolite belongs. The framework type is assigned for 1433 zeolite database entries in the FIZ/NIST Inorganic Crystal Structure Database (ICSD) populating 95 framework types. These entries correspond to both natural and synthetic zeolites. Each ICSD entry is based on published work containing crystallographic information of the zeolite crystalline structure and some physical and chemical data. Today, the Structure Commission of the International Zeolite Association recognizes crystalline materials as belonging to the ``zeolite'' family only if they possess one of the approved framework types by the organization. Such information is of fundamental importance for identifying zeolites, for reference, for zeolite standards, for supporting the discovery of new zeolites, and for crystalline substance selection based on application. Unfortunately, framework-type information is not contained in the ICSD records. The long term goal of this work is filling such gap. Although the ICSD contains an extensive collection of zeolites, inclusion of zeolites belonging to the 191 accepted framework types could substantially expand such collection. The structural determination was achieved via several structural analysis methods based on numerical-computer implementations.

Yang, Shujiang; Lach-Hab, Mohammed; Vaisman, Iosif I.; Blaisten-Barojas, Estela; Li, Xiang; Karen, Vicky L.

2010-09-01

328

Ordering the amorphous - Structures in PBD LED materials  

NASA Astrophysics Data System (ADS)

The class of 2,5 disubstituted-1,3,4-oxadiazoles containing a biphenyl unit on one side is intensively used as electron transport materials to enhance the performance of organic light emitting diodes (OLEDs). In contrast to the ongoing research on these materials insights in their structure-property relationships are still incomplete. To overcome the structural tentativeness and ambiguities the crystal structures of 2-(4-biphenylyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazole, that of the related compound 2-(4-biphenylyl)-5-phenyl-1,3,4-oxadiazole and of 2-(4-biphenylyl)-5-(2,6-dimethylphenyl)-1,3,4-oxadiazole are determined. A comparison with the results of GAUSSIAN03 calculations and similar compounds in the Cambridge Structural Database leads to a profound characterization.

Emmerling, Franziska; Orgzall, Ingo; Dietzel, Birgit; Schulz, Burkhard; Larrucea, Julen

2012-12-01

329

Local structure probes of nanoscale heterogeneity in crystalline materials.  

PubMed

In the conventional model of condensed matter increasing numbers of defects break down the order and ultimately convert perfect periodic crystals into aperiodic glasses. Local structure probes of a variety of materials with non-stoichiometric compositions, multiple degenerate ordering modes, or other symmetry breaking factors identify multiple ordered arrangements of atoms that render the materials heterogeneous on the nanometer scale. While exerting apparently negligible effects on bulk properties, this heterogeneity or phase separation does influence correlated or collective properties such as magnetism and phase stability. PMID:11512750

Conradson, S; Espinosa, F; Villella, P

2001-03-01

330

Crystal structure and physicochemical properties of doped lanthanum manganites  

NASA Astrophysics Data System (ADS)

Substituted lanthanum-strontium manganites La0.7Sr0.3Mn0.9Me0.1O3 ? (Me = Ti, Cr, Fe, and Cu) are obtained by standard ceramic and glycerin-nitrate techniques. High-temperature powder X-ray diffraction is employed to study the crystal structure of La0.7Sr0.3Mn0.9Me0.1O3 ? oxides. It is shown that in the range 298-1023 K in air, La0.7Sr0.3Mn0.9Me0.103 ? manganites crystallized in an orthorhombic cell (space group R-3c). The isobaric temperature dependences of unit cell parameters are determined. Thermal expansion coefficients are calculated for La0.7Sr0.3Mn0.9Me0.103 ? oxides. The conductivity of La0.7Sr0.3Mn0.9Me0.103 ? is studied as a function of temperature in the range 500 K ? T ? 1200 K in air. It is shown that substituting 3 d metal for manganese considerably lowers the conductivity of basic La0.7Sr0.3Mn0.9O3 ?. The chemical stability of iron-substituted manganite La0.7Sr0.3Mn0.9Fe0.1O3 ? is studied with respect to the electrolyte material.

Aksenova, T. V.; Gavrilova, L. Ya.; Cherepanov, V. A.

2012-12-01

331

Ultrasound-initiated structural transformations in liquid crystals (A review)  

Microsoft Academic Search

The results of the studies of structural transformations in liquid crystal layers with homeotropic and planar macrostructures\\u000a in the fields of longitudinal, surface, and shear ultrasonic waves are systematized and generalized.

O. A. Kapustina

2008-01-01

332

Crystal Structure and Molecular Motion of Solid Carbon Disulfide.  

National Technical Information Service (NTIS)

The crystal structure of CS2 was determined at two temperatures from intensity data measured with a proportional counter and a modified Weissenberg apparatus. The orthorhombic cell exhibited marked anisotropic thermal expansion. Positional and anisotropic...

N. C. Baenziger W. L. Duax

1967-01-01

333

A Trireticulate Crystal Structure: Trihydrogen Cobalticyanide and Trisilver Cobalticyanide.  

National Technical Information Service (NTIS)

The crystals trisilver cobalticyanide and trihydrogen cobalticyanide have been shown to have a trireticulate structure, with nearly regular cobalticyanide octahedra connected by nitrogen-silver-nitrogen bonds or by hydrogen bonds between the nitrogen atom...

L. Pauling P. Pauling

1968-01-01

334

Large single domain 123 material produced by seeding with single crystal rare earth barium copper oxide single crystals  

DOEpatents

A method of fabricating bulk YBa.sub.2 Cu.sub.3 O.sub.x where compressed powder oxides and/or carbonates of Y and Ba and Cu present in mole ratios to form YBa.sub.2 Cu.sub.3 O.sub.x are heated in the presence of a Nd.sub.1+x Ba.sub.2-x Cu.sub.3 O.sub.y seed crystal to a temperature sufficient to form a liquid phase in the YBa.sub.2 Cu.sub.3 O.sub.x while maintaining the seed crystal solid. The materials are slowly cooled to provide a YBa.sub.2 Cu.sub.3 O.sub.x material having a predetermined number of domains between 1 and 5. Crack-free single domain materials can be formed using either plate shaped seed crystals or cube shaped seed crystals with a pedestal of preferential orientation material.

Todt, Volker (Lemont, IL); Miller, Dean J. (Darien, IL); Shi, Donglu (Oak Park, OH); Sengupta, Suvankar (Columbus, OH)

1998-01-01

335

Structural and thermal characterization of a semiorganic NLO material: l-alanine cadmium chloride  

Microsoft Academic Search

l-Alaninium cadmium chloride (LACC), a semiorganic nonlinear optical material has been synthesized and its single crystal grown and characterized for its thermal, structural, linear and second order nonlinear optical properties. Powder SHG study shows that LACC is 1.5 times efficient as KDP. Its optical transparency goes down to 200nm comparable to the typical borate crystals like potassium pentaborate.

S. Dhanuskodi; K. Vasantha; P. A. Angeli Mary

2007-01-01

336

Bulk Crystal Growth of Nonlinear Optical Organic Materials Using Inverted Vertical Gradient Freeze Method  

NASA Technical Reports Server (NTRS)

A new process for producing large bulk single crystals of benzil (C6H5COCOC6H5) is reported in this paper. Good quality crystals have been successfully grown using this approach to crystal growth. This method seems to be very promising for other thermally stable NLO organic materials also. The entire contents vycor crucible 1.5 inch in diameter and 2 inch deep was converted to single crystal. Purity of the starting growth material is also an important factor in the final quality of the grown crystals. The entire crystal can be very easily taken out of the crucible by simple maneuvering. Initial characterization of the grown crystals indicated that the crystals are as good as other crystals grown by conventional Bridgman Stockbarger technique.

Choi, J.; Cruz, Magda; Metzl, R.; Wang, W. S.; Aggarwal, M. D.; Penn, Benjamin G.; Frazier, Donald O.

1998-01-01

337

HSCT materials and structures: An MDC perspective  

NASA Technical Reports Server (NTRS)

The key High Speed Civil Transport (HSCT) features which control the materials selection are discussed. Materials are selected based on weight and production economics. The top-down and bottoms-up approaches to material selection are compared for the Mach 2.4 study baseline aircraft. The key materials and structures related tasks which remain to be accomplished prior to proceeding with the building of the HSCT aircraft are examined.

Sutton, Jay O.

1992-01-01

338

Emissivity of Electronic Materials, Coatings, and Structures  

NASA Astrophysics Data System (ADS)

This study presents an overview of commonly used electronic materials and nanocoatings, as well as the evolution and significance of emissivity of commonly used electronic materials and nanocoatings. In addition, some key issues are addressed, such as accurate temperature measurements during materials processing and control as well as thermal management in high-power electronic device applications. Case studies of the optical properties of bulk materials, multilayered structures, and electronic devices, mainly bolometers, are discussed and analyzed for optimization.

Muley, Sarang V.; Ravindra, Nuggehalli M.

2014-04-01

339

Allophycocyanin and phycocyanin crystal structures reveal facets of phycobilisome assembly.  

PubMed

X-ray crystal structures of the isolated phycobiliprotein components of the phycobilisome have provided high resolution details to the description of this light harvesting complex at different levels of complexity and detail. The linker-independent assembly of trimers into hexamers in crystal lattices of previously determined structures has been observed in almost all of the phycocyanin (PC) and allophycocyanin (APC) structures available in the Protein Data Bank. In this paper we describe the X-ray crystal structures of PC and APC from Synechococcus elongatus sp. PCC 7942, PC from Synechocystis sp. PCC 6803 and PC from Thermosynechococcus vulcanus crystallized in the presence of urea. All five structures are highly similar to other PC and APC structures on the levels of subunits, monomers and trimers. The Synechococcus APC forms a unique loose hexamer that may show the structural requirements for core assembly and rod attachment. While the Synechococcus PC assembles into the canonical hexamer, it does not further assemble into rods. Unlike most PC structures, the Synechocystis PC fails to form hexamers. Addition of low concentrations of urea to T. vulcanus PC inhibits this proteins propensity to form hexamers, resulting in a crystal lattice composed of trimers. The molecular source of these differences in assembly and their relevance to the phycobilisome structure is discussed. PMID:23201474

Marx, Ailie; Adir, Noam

2013-03-01

340

Composite materials for space structures  

NASA Technical Reports Server (NTRS)

The use of advanced composites for space structures is reviewed. Barriers likely to limit further applications of composites are discussed and highlights of research to improve composites are presented. Developments in composites technology which could impact spacecraft systems are reviewed to identify technology needs and opportunities.

Tenney, D. R.; Sykes, G. F.; Bowles, D. E.

1985-01-01

341

Gallium arsenide single crystal solar cell structure and method of making  

NASA Technical Reports Server (NTRS)

A production method and structure for a thin-film GaAs crystal for a solar cell on a single-crystal silicon substrate (10) comprising the steps of growing a single-crystal interlayer (12) of material having a closer match in lattice and thermal expansion with single-crystal GaAs than the single-crystal silicon of the substrate, and epitaxially growing a single-crystal film (14) on the interlayer. The material of the interlayer may be germanium or graded germanium-silicon alloy, with low germanium content at the silicon substrate interface, and high germanium content at the upper surface. The surface of the interface layer (12) is annealed for recrystallization by a pulsed beam of energy (laser or electron) prior to growing the interlayer. The solar cell structure may be grown as a single-crystal n.sup.+ /p shallow homojunction film or as a p/n or n/p junction film. A Ga(Al)AS heteroface film may be grown over the GaAs film.

Stirn, Richard J. (Inventor)

1983-01-01

342

Crystal Structure of KinS2-I.  

National Technical Information Service (NTIS)

An X-ray single-crystal structure determination has confirmed that KInS2-I has the TIGaSe2 structure. The bonding in KIn S2-I is highly covalent and exhibits both two-dimensional and three-dimensinal features. The structure is comprised of layers of verte...

C. K. Lowe-Ma D. O. Kipp T. A. Vanderan

1990-01-01

343

Crystal Structure of Bacillus subtilis ?-Amylase in Complex with Acarbose  

PubMed Central

The crystal structure of Bacillus subtilis ?-amylase, in complex with the pseudotetrasaccharide inhibitor acarbose, revealed an hexasaccharide in the active site as a result of transglycosylation. After comparison with the known structure of the catalytic-site mutant complexed with the native substrate maltopentaose, it is suggested that the present structure represents a mimic intermediate in the initial stage of the catalytic process.

Kagawa, Masayuki; Fujimoto, Zui; Momma, Mitsuru; Takase, Kenji; Mizuno, Hiroshi

2003-01-01

344

Vortex structure in superconducting iron pnictide single crystals  

NASA Astrophysics Data System (ADS)

The vortex structure in the iron pnictide single crystals Ba1- x K x Fe2As2 and Sr1- x K x Fe2As2 of the 122 type and SmFeAsO1- x F x of the 1111 type has been investigated using the decoration method. In all of the crystals under investigation, no regular vortex lattice has been revealed in the magnetic field range up to 200 Oe. The disordered vortex structure is discussed in view of the vortex pinning in single crystals.

Vinnikov, L. Ya.; Artemova, T. M.; Veshchunov, I. S.; Zhigadlo, N. D.; Karpinski, J.; Popovich, P.; Sun, D. L.; Lin, C. T.; Boris, A. V.

2009-10-01

345

Biomimetic photonic materials with tunable structural colors.  

PubMed

Nature is a huge gallery of art involving nearly perfect structures and forms over the millions of years developing. Inspiration from natural structures exhibiting structural colors is first discussed. We give some examples of natural one-, two-, and three-dimensional photonic structures. This review article presents a brief summary of recent progress on bio-inspired photonic materials with variable structural colors, including the different facile and efficient routes to construct the nano-architectures, and the development of the artificial variable structural color photonic materials. Besides the superior optical properties, the excellent functions such as robust mechanical strength, good wettability are also mentioned, as well as the technical importance in various applications. This review will provide significant insight into the fabrication, design and application of the structural color materials. PMID:23816221

Xu, Jun; Guo, Zhiguang

2013-09-15

346

X-ray crystal structures of a severely desiccated protein.  

PubMed

Unlike most protein crystals, form IX of bovine pancreatic ribonuclease A diffracts well when severely dehydrated. Crystal structures have been solved after 2.5 and 4 days of desiccation with CaSO4, at 1.9 and 2.0 A resolution, respectively. The two desiccated structures are very similar. An RMS displacement of 1.6 A is observed for main-chain atoms in each structure when compared to the hydrated crystal structure with some large rearrangements observed in loop regions. The structural changes are the result of intermolecular contacts formed by strong electrostatic interactions in the absence of a high dielectric medium. The electron density is very diffuse for some surface loops, consistent with a very disordered structure. This disorder is related to the conformational changes. These results help explain conformational changes during the lyophilization of protein and the associated phenomena of denaturation and molecular memory. PMID:10548049

Bell, J A

1999-10-01

347

Quantitative crystal structure descriptors from multiplicative congruential generators.  

PubMed

Special types of number-theoretic relations, termed multiplicative congruential generators (MCGs), exhibit an intrinsic sublattice structure. This has considerable implications within the crystallographic realm, namely for the coordinate description of crystal structures for which MCGs allow for a concise way of encoding the numerical structural information. Thus, a conceptual framework is established, with some focus on layered superstructures, which proposes the use of MCGs as a tool for the quantitative description of crystal structures. The multiplicative congruential method eventually affords an algorithmic generation of three-dimensional crystal structures with a near-uniform distribution of atoms, whereas a linearization procedure facilitates their combinatorial enumeration and classification. The outlook for homometric structures and dual-space crystallography is given. Some generalizations and extensions are formulated in addition, revealing the connections of MCGs with geometric algebra, discrete dynamical systems (iterative maps), as well as certain quasicrystal approximants. PMID:22338652

Hornfeck, Wolfgang

2012-03-01

348

Synthesis, growth, structure determination and optical properties of chalcone derivative single crystal  

NASA Astrophysics Data System (ADS)

Acquiring large nonlinear optical (NLO) efficient organic material is essential for the development of optoelectronics and photonic devices. Chalcone is the donor - ? - acceptor - ? - donor (D-?-A-?-D) type conjugated molecule with appreciable hyperpolarizability of potential interest in NLO applications. The addition of vinyl and electron donor groups in the chalcone molecule may enhance the second harmonic generation (SHG) efficiency. Here we report the synthesis, crystal growth and characterization of a chalcone derivative 1-(4-methylphenyl)-5-(4-methoxyphenyl)-penta-2,4-dien-1-one (MPMPP). The MPMPP crystal was grown by slow evaporation solution growth technique from acetone. The grown crystal structure was studied by single crystal X-ray diffraction. The SHG efficiency of the grown crystal was determined by Kurtz and Perry method.

Karthi, S.; Girija, E. K.

2014-04-01

349

Radiation Effects on Spacecraft Structural Materials  

SciTech Connect

Research is being conducted to develop an integrated technology for the prediction of aging behavior for space structural materials during service. This research will utilize state-of-the-art radiation experimental apparatus and analysis, updated codes and databases, and integrated mechanical and radiation testing techniques to investigate the suitability of numerous current and potential spacecraft structural materials. Also included are the effects on structural materials in surface modules and planetary landing craft, with or without fission power supplies. Spacecraft structural materials would also be in hostile radiation environments on the surface of the moon and planets without appreciable atmospheres and moons around planets with large intense magnetic and radiation fields (such as the Jovian moons). The effects of extreme temperature cycles in such locations compounds the effects of radiation on structural materials. This paper describes the integrated methodology in detail and shows that it will provide a significant technological advance for designing advanced spacecraft. This methodology will also allow for the development of advanced spacecraft materials through the understanding of the underlying mechanisms of material degradation in the space radiation environment. Thus, this technology holds a promise for revolutionary advances in material damage prediction and protection of space structural components as, for example, in the development of guidelines for managing surveillance programs regarding the integrity of spacecraft components, and the safety of the aging spacecraft. (authors)

Wang, Jy-An J.; Ellis, Ronald J.; Hunter, Hamilton T. [Oak Ridge National Laboratory (United States); Singleterry, Robert C. Jr. [NASA Langley Research Center, Hampton, VA 23681 (United States)

2002-07-01

350

Mapping the Structure of Heterogeneous Materials  

NASA Technical Reports Server (NTRS)

Image-processing microdensitometer/Fourier analyzer yields statistics of subcomponent distribution. Nondestructive method for studying structure heterogeneous materials uses energy-dispersive X-ray analysis in scanning electron microscope. Scanning microdensitometer/Fourier analyzer (SMFA) is applied to SEM images to obtain statistics about sample structure. Method originally developed for studying effect on combustion of fine structure of composite solid propellants.

Strand, L. D.; Cohen, N. S.; Hernan, M. A.

1986-01-01

351

Development of the Structural Materials Information Center  

Microsoft Academic Search

The US Nuclear Regulatory Commission has initiated a Structural Aging Program at the Oak Ridge National Laboratory to identify potential structural safety issues related to continued service of nuclear power plants and to establish criteria for evaluating and resolving these issues. One of the tasks in this program focuses on the establishment of a Structural Materials Information Center where data

C. B. Oland; D. J. Naus

1990-01-01

352

Rational Design, Theory and Molecular Architecture of Highly Ordered Stilbene and Stilbazole Systems for Nonlinear Optical Materials: Pi-Electron Theoretical Studies, Crystal Structure, HighT Functionalized Polymers, and Self - Multilayer Superlattices  

Microsoft Academic Search

The construction of chromophoric self-assembled multilayers as an approach to the synthesis of thin-film second-order nonlinear optical (NLO) materials is described. The self-assembled chromophore-containing multilayer structures are built up in the repeating reaction sequence: I _3Si(CH_2) _2C_6H_4 CH_2I (Cp), 4- (N,N-bis(3 -hydroxypropyl)amino) styryl-4^' -pyridine (Ch), Cl_3SiOSiCl _2OSiCl_3 (Si), polyvinylalcohol (PVA). The multilayer structures have been characterized by optical and XPS

Dequan Li

1990-01-01

353

Rhombohedral cubic semiconductor materials on trigonal substrate with single crystal properties and devices based on such materials  

NASA Technical Reports Server (NTRS)

Growth conditions are developed, based on a temperature-dependent alignment model, to enable formation of cubic group IV, group II-V and group II-VI crystals in the [111] orientation on the basal (0001) plane of trigonal crystal substrates, controlled such that the volume percentage of primary twin crystal is reduced from about 40% to about 0.3%, compared to the majority single crystal. The control of stacking faults in this and other embodiments can yield single crystalline semiconductors based on these materials that are substantially without defects, or improved thermoelectric materials with twinned crystals for phonon scattering while maintaining electrical integrity. These methods can selectively yield a cubic-on-trigonal epitaxial semiconductor material in which the cubic layer is substantially either directly aligned, or 60 degrees-rotated from, the underlying trigonal material.

Park, Yeonjoon (Inventor); Choi, Sang Hyouk (Inventor); King, Glen C. (Inventor); Elliott, James R. (Inventor)

2012-01-01

354

Crystal and magnetic structures of hexagonal YMnO3.  

PubMed

The available data on the structural and magnetic transitions in multiferroic hexagonal YMnO3 have been reviewed, first making use of the computer programs from the group theoretical ISOTROPY software suite to list possible crystal and magnetic structures, then taking into account the capability of neutron diffraction and other physical methods to distinguish them. This leads to a clear view of the transformation sequence, as follows. Hexagonal YMnO3 is paraelectric in P63/mmc at elevated temperatures, and undergoes a single structural transition on cooling through 1250?K to a ferrielectric phase in P63cm that is retained through room temperature. At a much lower temperature, 70?K, there is a magnetic transition from paramagnetic to a triangular antiferromagnetic arrangement, most likely with symmetry P63'cm'. Comment is made on the unusual coupling of ferroelectric and magnetic domains reported to occur in this material, as well as on the so-called `giant magneto-elastic' effect. PMID:24253077

Howard, Christopher J; Campbell, Branton J; Stokes, Harold T; Carpenter, Michael A; Thomson, Richard I

2013-12-01

355

crystals  

NASA Astrophysics Data System (ADS)

A novel combined interferometric-mask method for the formation of micro- and nanometric scale three-dimensional (3D) rotational symmetry quasi-crystalline refractive lattice structures in photorefractive materials is demonstrated experimentally. The method is based on micrometric scale spatial modulation of the light by amplitude mask in the radial directions and along the azimuthal angle and the use of counter-propagating beam geometry building up Gaussian standing wave, which defines the light modulation in the axial direction with half-wavelength periodicity. 3D intensity pattern can be represented as numerous mask-generated 2D quasi-periodic structures located in each anti-node of the standing wave. The formed 3D intensity distributions of the optical beams can be imparted into the photorefractive medium thus creating the micro- and sub-micrometric scale 3D refractive index volume lattices. The used optical scheme allows also the formation of 2D lattices by removing the back-reflecting mirror. 2D and 3D refractive lattices were recorded with the use of 532 nm laser beam and rotational symmetry mask in doped lithium niobate crystals and were tested by the probe beam far-field diffraction pattern imaging and direct observation by phase microscope. The formed rotational symmetry 3D refractive structures have the periods of 20-60 ?m in the radial directions, 60 ?m along the azimuthal angle and half-wavelength 266 nm in the axial direction.

Badalyan, A.; Hovsepyan, R.; Mantashyan, P.; Mekhitaryan, V.; Drampyan, R.

2014-07-01

356

Energy absorption of composite material and structure  

NASA Technical Reports Server (NTRS)

Results are presented from a joint research program on helicopter crashworthiness conducted by the U.S. Army Aerostructures Directorate and NASA Langley. Through the ongoing research program an in-depth understanding has been developed on the cause/effect relationships between material and architectural variables and the energy-absorption capability of composite material and structure. Composite materials were found to be efficient energy absorbers. Graphite/epoxy subfloor structures were more efficient energy absorbers than comparable structures fabricated from Kevlar or aluminum. An accurate method of predicting the energy-absorption capability of beams was developed.

Farley, Gary L.

1987-01-01

357

Crystal structure control in Au-free self-seeded InSb wire growth.  

PubMed

In this work we demonstrate experimentally the dependence of InSb crystal structure on the ratio of Sb to In atoms at the growth front. Epitaxial InSb wires are grown by a self-seeded particle assisted growth technique on several different III-V substrates. Detailed investigations of growth parameters and post-growth energy dispersive x-ray spectroscopy indicate that the seed particles initially consist of In and incorporate up to 20at.% Sb during growth. By applying this technique we demonstrate the formation of zinc-blende, 4H and wurtzite structure in the InSb wires (identified by transmission electron microscopy and synchrotron x-ray diffraction), and correlate this sequential change in crystal structure to the increasing Sb/In ratio at the particle-wire interface. The low ionicity of InSb and the large diameter of the wire structures studied in this work are entirely outside the parameters for which polytype formation is predicted by current models of particle seeded wire growth, suggesting that the V/III ratio at the interface determines crystal structure in a manner well beyond current understanding. These results therefore provide important insight into the relationship between the particle composition and the crystal structure, and demonstrate the potential to selectively tune the crystal structure in other III-V compound materials as well. PMID:21346304

Mandl, Bernhard; Dick, Kimberly A; Kriegner, Dominik; Keplinger, Mario; Bauer, Gnther; Stangl, Julian; Deppert, Knut

2011-04-01

358

Revolutionary opportunities for materials and structures study  

NASA Technical Reports Server (NTRS)

The revolutionary opportunities for materials and structures study was performed to provide Government and Industry focus for advanced materials technology. Both subsonic and supersonic engine studies and aircraft fuel burn and DOC evaluation are examined. Year 2010 goal materials were used in the advanced engine studies. These goal materials and improved component aero yielded subsonic fuel burn and DOC improvements of 13.4 percent and 5 percent, respectively and supersonic fuel burn and DOC improvements of 21.5 percent and 18 percent, respectively. Conclusions are that the supersonic study engine yielded fuel burn and DOC improvements well beyond the program goals; therefore, it is appropriate that advanced material programs be considered.

Schweiger, F. A.

1987-01-01

359

Structural diversity of bulky graphene materials.  

PubMed

The unique two-dimensional (2D) structure and chemical properties of graphene and its derivatives make it a distinctive nanoscale building block for constructing novel bulky architectures with different dimensions, such as 1D fibers, 2D films and 3D architectures. These bulky graphene materials, depending on the manner in which graphene sheets are assembled, show a variety of fascinating features that cannot be achieved from individual graphene sheet or conventional materials. Thus, over the past several years, considerable effort has been expended in fabricating various structures of bulky graphene materials and developing their corresponding applications. Here, we present a broad and comprehensive overview of the recent developments in expanding the structural diversity of bulky graphene materials and their applications in energy storage and conversion, composites, environmental remediation, etc. Finally, prospects and further developments in this exciting field of bulky graphene materials are also suggested. PMID:24668900

Liu, Lili; Niu, Zhiqiang; Zhang, Li; Chen, Xiaodong

2014-06-01

360

Role of defects in radiation chemistry of crystalline organic materials. 3. Geometrical and electronic structures of alkene radical anion and cation in alkene/n-alkane mixed crystals as studied by ESR spectroscopy  

SciTech Connect

An ESR study has been made in order to elucidate the electronic structures of alkene radical anions and cations, the former radicals being first detected in the hexene/n-hexene mixed crystals irradiated at 4.2 K along with the cation. The present work extended to the hexene and butene isomers has resulted in evidence that both anions with vinylene and vinylidene groups have pyramidal structures with {sigma}-character, which differ from the planar or twisted structures of corresponding cations. The proton hyperfine couplings of their anions were only about one-third as large as those for the cations: {vert bar}A{vert bar}(two {alpha}-H) = {vert bar}0.45, 0.1, {minus}0.25{vert bar} mT; a (two pairs of {beta}-H) = 1.38 and 0.56 mT for the 3-hexene anion, and a(two {alpha}-H) = 1.3 mT and a(two pairs of {beta}-H) = 4.6 and 2.9 mT for the cation. The differences in the geometrical structures and in the sizes of the proton couplings of the anion and cation radicals were discussed on the basis of a simple molecular orbital calculation. It has been found that the anion is stabilized by admixing {vert bar}2s;C> atomic orbitals (AO) with a lower core integral than {vert bar}2p;C> AO to the unpaired electron orbital and that the small {beta}-proton couplings mainly originate from low extent of hyperconjugation due to a wide energy separation of C{double bond}C {pi}-antibonding and C-H pseudo-{pi}-bonding orbitals.

Matsuura, Kaoru; Muto, Hachizo; Nunome, Keichi (Government Industrial Research Inst., Nagoya (Japan))

1991-11-14

361

In situ studies of a platform for metastable inorganic crystal growth and materials discovery.  

PubMed

Rapid shifts in the energy, technological, and environmental demands of materials science call for focused and efficient expansion of the library of functional inorganic compounds. To achieve the requisite efficiency, we need a materials discovery and optimization paradigm that can rapidly reveal all possible compounds for a given reaction and composition space. Here we provide such a paradigm via in situ X-ray diffraction measurements spanning solid, liquid flux, and recrystallization processes. We identify four new ternary sulfides from reactive salt fluxes in a matter of hours, simultaneously revealing routes for ex situ synthesis and crystal growth. Changing the flux chemistry, here accomplished by increasing sulfur content, permits comparison of the allowable crystalline building blocks in each reaction space. The speed and structural information inherent to this method of in situ synthesis provide an experimental complement to computational efforts to predict new compounds and uncover routes to targeted materials by design. PMID:25024201

Shoemaker, Daniel P; Hu, Yung-Jin; Chung, Duck Young; Halder, Gregory J; Chupas, Peter J; Soderholm, L; Mitchell, J F; Kanatzidis, Mercouri G

2014-07-29

362

Crystal Structures of Two Putative Phosphoheptose  

SciTech Connect

Structural genomic centers use both NMR spectroscopic and X-ray crystallographic methods to determine three-dimensional structures of proteins on a genomic scale in a high-throughput mode and to deposit in the PDB. The main goal of structural genomics is to determine a large number of protein structures to complement the ever-expanding database of genome sequences. Another role of structural genomics is to delineate the correspondence between sequence and structure space; a number of protein structures from otherwise unrelated (i.e., 8-10% sequence identity) families often prove to have remarkably similar folds. This finding, in turn, allows better understanding of the structure-function relationships in those proteins for which either structures are not available or cannot be experimentally determined.

Seetharaman,J.; Rajashankar, K.; Solarzano, V.; Kniewel, R.; Lima, C.; Bonanno, J.; Burley, S.; Swaminathan, S.

2006-01-01

363

Spectroscopic and structural studies of L-arginine doped Potassium Dihydrogen Phosphate crystals  

NASA Astrophysics Data System (ADS)

We report in this study the spectroscopic and structural characterization of standard and L-arginine doped potassium dihydrogen phosphate crystals synthesized by a solution growth technique. The infrared absorption and Raman results demonstrate chemical functionalization between the amino (NH3^+) groups of the organic material and the phosphate units of the inorganic crystals. This affirmation, which also implies the achievement of successful doping, is supported by the existence of extra vibrational lines in the IR and Raman spectra of L-arginine doped potassium dihydrogen phosphate crystals; these vibrational lines exhibit shifting towards lower frequencies as compared with the characteristic bands of L-arginine. Incorporation of the amino acid into the structure of the inorganic material is revealed by X-ray diffraction results also, where the shifting of diffraction lines and the appearance of a new one are observed.

Govani, Jayesh; Botez, Cristian; Durrer, William; Manciu, Felicia

2009-03-01

364

Crystallization of dienelactone hydrolase in two space groups: structural changes caused by crystal packing.  

PubMed

Dienelactone hydrolase (DLH) is a monomeric protein with a simple ?/?-hydrolase fold structure. It readily crystallizes in space group P212121 from either a phosphate or ammonium sulfate precipitation buffer. Here, the structure of DLH at 1.85? resolution crystallized in space group C2 with two molecules in the asymmetric unit is reported. When crystallized in space group P212121 DLH has either phosphates or sulfates bound to the protein in crucial locations, one of which is located in the active site, preventing substrate/inhibitor binding. Another is located on the surface of the enzyme coordinated by side chains from two different molecules. Crystallization in space group C2 from a sodium citrate buffer results in new crystallographic protein-protein interfaces. The protein backbone is highly similar, but new crystal contacts cause changes in side-chain orientations and in loop positioning. In regions not involved in crystal contacts, there is little change in backbone or side-chain configuration. The flexibility of surface loops and the adaptability of side chains are important factors enabling DLH to adapt and form different crystal lattices. PMID:25005082

Porter, Joanne L; Carr, Paul D; Collyer, Charles A; Ollis, David L

2014-07-01

365

Single-crystal growth, crystal and electronic structure of NaCoO 2  

Microsoft Academic Search

Single crystals of NaCoO2 have been successfully synthesized for the first time by a flux method at 1323K. A single-crystal X-ray diffraction study confirmed the trigonal R3?m space group and the lattice parameters a=2.8897(15)A?, c=15.609(3)A?. The crystal structure has been refined to the conventional values R=1.9% and wR=2.1% for 309 independent observed reflections. The electron density distribution of NaCoO2 has

Yasuhiko Takahashi; Yoshito Gotoh; Junji Akimoto

2003-01-01

366

Datamining protein structure databanks for crystallization patterns of proteins.  

PubMed

A study of 345 protein structures selected among 1,500 structures determined by nuclear magnetic resonance (NMR) methods, revealed useful correlations between crystallization properties and several parameters for the studied proteins. NMR methods of structure determination do not require the growth of protein crystals, and hence allow comparison of properties of proteins that have or have not been the subject of crystallographic approaches. One- and two-dimensional statistical analyses of the data confirmed a hypothesized relation between the size of the molecule and its crystallization potential. Furthermore, two-dimensional Bayesian analysis revealed a significant relationship between relative ratio of different secondary structures and the likelihood of success for crystallization trials. The most immediate result is an apparent correlation of crystallization potential with protein size. Further analysis of the data revealed a relationship between the unstructured fraction of proteins and the success of its crystallization. Utilization of Bayesian analysis on the latter correlation resulted in a prediction performance of about 64%, whereas a two-dimensional Bayesian analysis succeeded with a performance of about 75%. PMID:12594078

Valafar, Homayoun; Prestegard, James H; Valafar, Faramarz

2002-12-01

367

Ultrafast characterization of phase-change material crystallization properties in the melt-quenched amorphous phase.  

PubMed

Phase change materials are widely considered for application in nonvolatile memories because of their ability to achieve phase transformation in the nanosecond time scale. However, the knowledge of fast crystallization dynamics in these materials is limited because of the lack of fast and accurate temperature control methods. In this work, we have developed an experimental methodology that enables ultrafast characterization of phase-change dynamics on a more technologically relevant melt-quenched amorphous phase using practical device structures. We have extracted the crystallization growth velocity (U) in a functional capped phase change memory (PCM) device over 8 orders of magnitude (10(-10) < U < 10(-1) m/s) spanning a wide temperature range (415 < T < 580 K). We also observed direct evidence of non-Arrhenius crystallization behavior in programmed PCM devices at very high heating rates (>10(8) K/s), which reveals the extreme fragility of Ge2Sb2Te5 in its supercooled liquid phase. Furthermore, these crystallization properties were studied as a function of device programming cycles, and the results show degradation in the cell retention properties due to elemental segregation. The above experiments are enabled by the use of an on-chip fast heater and thermometer called as microthermal stage (MTS) integrated with a vertical phase change memory (PCM) cell. The temperature at the PCM layer can be controlled up to 600 K using MTS and with a thermal time constant of 800 ns, leading to heating rates ?10(8) K/s that are close to the typical device operating conditions during PCM programming. The MTS allows us to independently control the electrical and thermal aspects of phase transformation (inseparable in a conventional PCM cell) and extract the temperature dependence of key material properties in real PCM devices. PMID:24798660

Jeyasingh, Rakesh; Fong, Scott W; Lee, Jaeho; Li, Zijian; Chang, Kuo-Wei; Mantegazza, Davide; Asheghi, Mehdi; Goodson, Kenneth E; Wong, H-S Philip

2014-06-11

368

Assessment of New Materials Synthesis and Crystal Growth in United States, (Final Report).  

National Technical Information Service (NTIS)

The committee of 16 members was drawn from the broad community of condensed-matter physicists and materials researchers, and included experts in bulk materials synthesis and crystal growth (oxide, intermetallic, semiconductor, and organic synthesis) and b...

D. C. Shapero J. C. Lancaster

2009-01-01

369

Crystal Structures and Band Structures of Acene Chalcogenides: Their Application for OFET.  

NASA Astrophysics Data System (ADS)

We have systematically studied acene chalcogenides as active channel materials for Organic Field Effect Transistor (OFET). The molecules have a common structural feature which is of great advantage for carrier channel: chalcogen atoms are located at outside of molecule so that larger orbitals of chalcogen atoms would intensify intermolecular interactions not only for the molecular stacking direction but also for the inter-stacking directions. We then expect that the conduction channels would become more isotropic and the effective mass of the carriers would become lighter compared to the case of aromatic hydrocarbons. The materials we have surveyed are as follows: Hexathiopentacene (HTP), Tetrathiotetracene (TTT), Hexathioanthracene (HTA), Tetrathioanthracene (TTA), Benzo[1,2-c;3,4-c';5,6-c'']tris[1,2]dithiole-1,4,7-trithione (abbreviated as C9S9, which is its chemical formula), and some selenium analogues. The first-principle band structure calculations based on the crystal structures determined by x-ray analysis reveal that the materials have an anisotropic 2-D HOMO band with an effective mass of 1.1me for TSeA, 1.3me for HTA, 1.4me for TTT, respectively. HTP is proved to have a 1-D HOMO band with m*=2.5me in spite of 2-D structural feature. It is interesting that C9S9 has an isotropic 3-D HOMO band with m*=0.68me, properties which are suitable for OFET channel.

Ugawa, A.

2005-03-01

370

Crystal and quasicrystal structures in Al-Mn-Si alloys  

Microsoft Academic Search

It is shown that the alpha-(AlMnSi) crystal structure is closely (and systematically) related to that of the icosahedral Al-Mn-Si alloys. Using a modification of the 'projection' method of generating icosahedral structures from six-dimensional lattices, a simple description of the alpha-(AlMnSi) structure is found. This structure, and (it is conjectured) the icosahedral one, can also be described as a packing of

Veit Elser; C. L. Henley

1985-01-01

371

Single-crystal structure of a covalent organic framework.  

PubMed

The crystal structure of a new covalent organic framework, termed COF-320, is determined by single-crystal 3D electron diffraction using the rotation electron diffraction (RED) method for data collection. The COF crystals are prepared by an imine condensation of tetra-(4-anilyl)methane and 4,4'-biphenyldialdehyde in 1,4-dioxane at 120 C to produce a highly porous 9-fold interwoven diamond net. COF-320 exhibits permanent porosity with a Langmuir surface area of 2400 m(2)/g and a methane total uptake of 15.0 wt % (176 cm(3)/cm(3)) at 25 C and 80 bar. The successful determination of the structure of COF-320 directly from single-crystal samples is an important advance in the development of COF chemistry. PMID:24143961

Zhang, Yue-Biao; Su, Jie; Furukawa, Hiroyasu; Yun, Yifeng; Gndara, Felipe; Duong, Adam; Zou, Xiaodong; Yaghi, Omar M

2013-11-01

372

Crystal structure of potassium titanyl phosphate doped with zirconium  

SciTech Connect

This paper reports on the results of precision X-ray structural investigations of single crystals of the compounds KTi{sub 0.96}Zr{sub 0.04}OPO{sub 4} (at 293 K) and KTi{sub 0.97}Zr{sub 0.03}OPO{sub 4} (at 293 and 105 K). No significant splitting of the positions occupied by potassium atoms is revealed. This result is in agreement with a considerable decrease in the electrical conductivity of potassium titanyl phosphate KTiOPO{sub 4} (KTP) crystals doped with zirconium (KTP: Zr) as compared to crystals of undoped potassium titanyl phosphate. It is established that the difference between the Ti-O bond lengths in chains formed by titanium octahedra is not a single structural parameter responsible for the nonlinear optical properties of crystals in this series.

Alekseeva, O. A., E-mail: olalex@ns.crys.ras.ru; Dudka, A. P.; Sorokina, N. I. [Russian Academy of Sciences, Shubnikov Institute of Crystallography (Russian Federation); Pietraszko, A. [Polish Academy of Sciences, Institute of Low Temperature and Structure Research (Poland); Rabadanov, M. Kh. [Russian Academy of Sciences, Shubnikov Institute of Crystallography (Russian Federation); Agapova, E. I.; Voronkova, V. I. [Lomonosov Moscow State University (Russian Federation); Simonov, V. I. [Russian Academy of Sciences, Shubnikov Institute of Crystallography (Russian Federation)

2007-07-15

373

Vulcanite, CuTe: hydrothermal synthesis and crystal structure refinement  

Microsoft Academic Search

Summary The crystal structure of the mineral vulcanite, CuTe [a?=?3.155(1), b?=?4.092(1), c?=?6.956(1)?; Z?=?2; space group: Pmmn,\\u000a No. 59] exhibits a pronounced layer structure with Te-Te distances between the CuTe layers of 4.019(1)?. Within a range up\\u000a to 4.2? the individual Cu atom is [4Te+4Cu+2Cu], the individual Te atom [4Cu+2Te+4Te] coordinated. Crystals of vulcanite\\u000a suitable for the present structure investigation were

F. Pertlik

2001-01-01

374

Symmetry building Monte Carlo-based crystal structure prediction  

NASA Astrophysics Data System (ADS)

Methods are presented that allow for the automatic increase and preservation of symmetry during global optimization of crystal structures. This systematic building of symmetry allows for its incorporation into structure prediction simulations even when the space group information is not known a priori. It is shown that simulations that build and maintain symmetry converge much more rapidly to ground state crystal structures than when symmetry is ignored, allowing for the treatment of unit cells much larger than would otherwise be possible, especially when beginning from the P1 space group.

Michel, Kyle Jay; Wolverton, C.

2014-05-01

375

Atomic- Resolution Crystal Structure of the Antiviral Lectin Scytovirin  

SciTech Connect

The crystal structures of the natural and recombinant antiviral lectin scytovirin (SVN) were solved by single-wavelength anomalous scattering and refined with data extending to 1.3 Angstroms and 1.0 Angstroms resolution, respectively. A molecule of SVN consists of a single chain 95 amino acids long, with an almost perfect sequence repeat that creates two very similar domains (RMS deviation 0.25 Angstroms for 40 pairs of Ca atoms). The crystal structure differs significantly from a previously published NMR structure of the same protein, with the RMS deviations calculated separately for the N- and C-terminal domains of 5.3 Angstroms and 3.7 Angstroms, respectively, and a very different relationship between the two domains. In addition, the disulfide bonding pattern of the crystal structures differs from that described in the previously published mass spectrometry and NMR studies.

Moulaei,T.; Botos, I.; Ziolkowska, N.; Bokesch, H.; Krumpe, L.; McKee, T.; O'Keefe, B.; Dauter, Z.; Wlodawer, A.

2007-01-01

376

Crystal structure of a theta-class glutathione transferase.  

PubMed Central

Glutathione S-transferases (GSTs) are a family of enzymes involved in the cellular detoxification of xenotoxins. Cytosolic GSTs have been grouped into four evolutionary classes for which there are representative crystal structures of three of them. Here we report the first crystal structure of a theta-class GST. So far, all available GST crystal structures suggest that a strictly conserved tyrosine near the N-terminus plays a critical role in the reaction mechanism and such a role has been convincingly demonstrated by site-directed mutagenesis. Surprisingly, the equivalent residue in the theta-class structure is not in the active site, but its role appears to have been replaced by either a nearby serine or by another tyrosine residue located in the C-terminal domain of the enzyme. Images

Wilce, M C; Board, P G; Feil, S C; Parker, M W

1995-01-01

377

Optical and structural properties of chalcone NLO single crystals  

NASA Astrophysics Data System (ADS)

Organic compound (E)-1-(4-methoxyphenyl)-3-(2,3,5-trichlorophenyl)prop-2-en-1-one [MPTCPP] with molecular formula C 16H 11Cl 3O 2 was synthesized using Claisen-Schmidt condensation reaction method. 1H NMR spectra was recorded to identify the various functional groups present in the compound and confirm the chemical structure. The single crystals were grown using slow evaporation solution growth technique. The UV-Visible spectrum study reveals that the crystal is transparent in the entire visible region and the absorption is observed at 364 nm. The Kurtz powder second harmonic generation (SHG) test shows that the MPTCPP is NLO active and its SHG efficiency is three times that of urea. Single crystal XRD study shows that the compound crystallizes in the monoclinic system with a space group Cc. The corresponding lattice parameters of the crystal are a = 28.215(5) , b = 3.9740(4) , c = 16.178(3) and V = 1503.0(4) 3. The micro hardness test was carried out and the work hardening coefficient value ( n) of the crystal was found to be 1.48. This indicates that the crystal is hard and is suitable for device application. The thermal study reveals that the thermal stability of the crystal is good.

Rajesh Kumar, P. C.; Ravindrachary, V.; Janardhana, K.; Manjunath, H. R.; Karegouda, Prakash; Crasta, Vincent; Sridhar, M. A.

2011-11-01

378

Refined Crystal Structures of Unligated Adenylosuccinate Synthetase from Escherichia coli  

Microsoft Academic Search

Crystal structures of unligated adenylosuccinate synthetase fromEscherichia coliin space groupsP21andP212121have been refined toR-factors of 0.199 and 0.206 against data to 2.0 and 2.5 , respectively. Bond lengths and angles deviate from expected values by 0.011 and 1.7 for theP21crystal form and by 0.015 and 1.7 for theP212121crystal form. The fold of the polypeptide chain is dominated by a

M. Mercedes Silva; Bradley W. Poland; Chad R. Hoffman; Herbert J. Fromm; Richard B. Honzatko

1995-01-01

379

Chemical space sampling in virtual screening by different crystal structures.  

PubMed

Retrospective virtual screening experiments were carried out to investigate the effects of combining hit lists from different crystal structures of the same target using consensus scoring. An in-house High Throughput Screening (HTS) dataset from PI3K-? was used and docked against five diverse PI3K-? crystal structures. The results show that consensus scoring prioritizes compounds that score moderately against individual crystal structures and is thus complementary to individual crystal structure screening leading to an increase in the diversity of hits. Enrichment factors (EFs) of the consensus score for two or three structures are often as high as or higher than the EF of the individual structures used in the consensus score. Combining four or five structures in the consensus score generally yields lower enrichments. Compounds in the top 500 of the consensus score that are also found in the top 500 of an individual X-ray structure used in the consensus score calculations yield the largest number of hits with the lowest number of false positives. PMID:20958920

Brooijmans, Natasja; Humblet, Christine

2010-12-01

380

Photonic crystals of diamond spheres with the opal structure  

NASA Astrophysics Data System (ADS)

Opal samples consisting of diamond spheres have been synthesized by chemical deposition in microwave plasma from a CH4/H2 mixture using templates of silicon inverse opal. The optical investigations have confirmed that the periodic structures prepared are structurally perfect three-dimensional photonic crystals.

Sovyk, D. N.; Ralchenko, V. G.; Kurdyukov, D. A.; Grudinkin, S. A.; Golubev, V. G.; Khomich, A. A.; Konov, V. I.

2013-05-01

381

Crystal structure of simple metals at high pressures  

Microsoft Academic Search

The effects of pressure on the crystal structure of simple (or sp-) elements are analysed in terms of changes in coordination number, packing density, and interatomic distances, and general rules are established. In the polyvalent elements from groups 1417, the covalently bonded structures tend to transform to metallic phases with a gradual increase in coordination number and packing density, a

Olga Degtyareva; Olga

2010-01-01

382

Etching effect on periodic domain structures of lithium niobate crystals  

Microsoft Academic Search

In order to improve the knowledge of the domain structure in LiNbO3 crystals, the effect of the etching process with HF:HNO3 (1:2 by vol.) has been studied. It has been found, by analyzing the superficial composition with the secondary ion mass spectrometry technique, that during the etching treatment, the fluorine ion diffuses into the crystal, mainly along the positive ferroelectric

V. Bermdez; F Caccavale; C Sada; F Segato; E Diguez

1998-01-01

383

Etching effect on periodic domain structures of lithium niobate crystals  

NASA Astrophysics Data System (ADS)

In order to improve the knowledge of the domain structure in LiNbO 3 crystals, the effect of the etching process with HF : HNO 3 (1 : 2 by vol.) has been studied. It has been found, by analyzing the superficial composition with the secondary ion mass spectrometry technique, that during the etching treatment, the fluorine ion diffuses into the crystal, mainly along the positive ferroelectric domain.

Bermdez, V.; Caccavale, F.; Sada, C.; Segato, F.; Diguez, E.

1998-07-01

384

Structure of blue phase III of cholesteric liquid crystals.  

PubMed

We report large scale simulations of the blue phases of cholesteric liquid crystals. Our results suggest a structure for blue phase III, the blue fog, which has been the subject of a long debate in liquid crystal physics. We propose that blue phase III is an amorphous network of disclination lines, which is thermodynamically and kinetically stabilized over crystalline blue phases at intermediate chiralities. This amorphous network becomes ordered under an applied electric field, as seen in experiments. PMID:21469836

Henrich, O; Stratford, K; Cates, M E; Marenduzzo, D

2011-03-11

385

The Host Guest Co-Crystal Approach to Supramolecular Structure  

Microsoft Academic Search

A host-guest co-crystal approach to supramolecular structure has been developed. Molecular functionalities have been identified that will self assemble via hydrogen bonds to give one dimensional ?-networks with defined intermolecular distances. Host molecules based on these functionalites can be co-crystallized with guest molecules, the characteristic distance defined by the host is thus imposed on the guest. Using this strategy, functional

John J. Kane; Tam Nguyen; Jun Xiao; Frank W. Fowler; Joseph W. Lauher

2001-01-01

386

Crystal structure of the extracellular segment of integrin V3  

Microsoft Academic Search

Integrins are heterodimeric receptors that mediate divalent cation-dependent cell-cell and cell-matrix adhesion through tightly regulated interactions with ligands. We have solved the crystal structure of the extracellular portion of integrin V{sup }3 at 3.1 Angstroms resolution. Its 12 domains assemble into an ovoid 'head' and two 'tails.' In the crystal, V{sup }3 is severely bent at a defined region in

J.-P. Xiong; T. Stehle; B. Diefenbach; R. Zhang; R. Dunker; D. L. Scott; A. Joachimiak; S. L. Goodman; M. A. Arnaout; Merck KGaA

2001-01-01

387

Observation and Analysis of Polymer Crystal Structures at the Stem Level. Implications Regarding Polymer Crystallization Processes.  

NASA Astrophysics Data System (ADS)

The building element of chain folded polymer crystals is the individual stem that spans the lamellar thickness. For chiral but racemic helical polymers such as polyolefins (e.g. isotactic and syndiotactic polypropylene and poly(1-butene)), stems can be right- or left-handed helices. These polymers can exist in various crystal polymorphs that are either "racemic" or "chiral" (made of both, or of only one helical hand). Upon crystallization, each stem has a conformational "choice", but must adapt to the crystal structure and, once crystallized, is characterized by a "conformational tag" (right or left hand). Various means exist to determine or observe helical hands in polyolefin lamellae: Atomic Force Microscopy on epitaxially crystallized samples, or, for the alpha phase of isotactic polypropylene, analysis of its specific lamellar branching. These observations and analyses indicate that the helical hand of stems is tightly determined by the substrate or growth face topography, i.e. indicate that the depositing stem probes and adapts to the surface structure prior to successful attachment. This "post-mortem" analysis of the crystal structure and stem chirality emphasizes the "sequential" nature of the growth process (successive attachment of individual stems). It is in line with early views on polymer crystallization. It is at variance with recently introduced models or scenarios that assume either some pre-ordering of the polymer melt as a result of spinodal decomposition and/or accretion of polymer chains in pseudo-crystalline bundles followed by (solid state) reorganization of the bundles to generate fully grown lamellae.

Lotz, Bernard

2003-03-01

388

Structure of ice crystallized from supercooled water  

PubMed Central

The freezing of water to ice is fundamentally important to fields as diverse as cloud formation to cryopreservation. At ambient conditions, ice is considered to exist in two crystalline forms: stable hexagonal ice and metastable cubic ice. Using X-ray diffraction data and Monte Carlo simulations, we show that ice that crystallizes homogeneously from supercooled water is neither of these phases. The resulting ice is disordered in one dimension and therefore possesses neither cubic nor hexagonal symmetry and is instead composed of randomly stacked layers of cubic and hexagonal sequences. We refer to this ice as stacking-disordered ice I. Stacking disorder and stacking faults have been reported earlier for metastable ice I, but only for ice crystallizing in mesopores and in samples recrystallized from high-pressure ice phases rather than in water droplets. Review of the literature reveals that almost all ice that has been identified as cubic ice in previous diffraction studies and generated in a variety of ways was most likely stacking-disordered ice I with varying degrees of stacking disorder. These findings highlight the need to reevaluate the physical and thermodynamic properties of this metastable ice as a function of the nature and extent of stacking disorder using well-characterized samples.

Malkin, Tamsin L.; Murray, Benjamin J.; Brukhno, Andrey V.; Anwar, Jamshed; Salzmann, Christoph G.

2012-01-01

389

Crystal and Magnetic Structure of UNi0.52  

NASA Astrophysics Data System (ADS)

We report the single crystal neutron diffraction studies done to resolve the room-temperature structure and the magnetic structure at 25 K of Uranium antimonide, UNi0.5Sb2. The time-of-flight single-crystal neutron diffraction experiments at room temperature and 25 K were done on the Single Crystal Diffractometer, SCD, at Los Alamos Neutron Science Center. Previous X-ray single crystal and neutron powder diffraction studies could not unambiguously resolve the structure because of the presence of hkl/2 type reflections. The studies were done on a 2 x 1 x 0.5 mm3 crystal and half-indexed reflections were observed corroborating the observations in previous studies. The room temperature structure that accounts for all the observed reflections is determined to be tetragonal P42/n m c with lattice parameters a = 4.333(2) and c = 17.868(6) respectively. The compound is found to order antiferromagnetically at 162 K and has a simple antiferromagnetic structure at 25 K with propagation vector q = (0, 0, 0) and with a moment of 1.82?B/U atom.

Kothapalli, Karunakar; Torikachvili, Milton; Nasreen, Farzana; Nakotte, Heinrich

2010-10-01

390

Fine Structure of Electron Diffraction Beams from a Gold Crystal and from a Silver Film on a Gold Crystal  

Microsoft Academic Search

A study of the diffraction of low-speed electrons from a gold crystal has been made under the same conditions as those previously used for a silver crystal to determine the extent to which the previously observed fine structure characteristics depend on the nature of the atoms composing the crystal. For normal incidence there are many differences in the positions, structure,

H. E. Farnsworth

1933-01-01

391

Synthesis, growth, structural, spectroscopic and optical studies of a semiorganic NLO crystal: zinc guanidinium phosphate.  

PubMed

The semi-organic nonlinear optical (NLO) crystal, zinc guanidinium phosphate (ZGuP) has been grown through synthesis between zinc sulphate, guanidine carbonate and orthophosphoric acid from its aqueous solution by slow solvent evaporation technique. Solubility of the synthesized material has been determined for various temperatures using water as solvent. The grown crystal has been characterized by powder X-ray diffraction to confirm the crystal structure. Investigation has been carried out to assign the vibrational frequencies of the grown crystals by Fourier transform infrared spectroscopy technique. (1)H and (13)C FT-NMR have been recorded to elucidate the molecular structure. The optical absorption study confirms the suitability of the crystal for device applications. The second harmonic generation (SHG) efficiency of ZGuP is found to be 1.825 times that of potassium dihydrogen phosphate (KDP). Thermal behavior of the grown crystals has been studied by thermogravimetric and differential thermal analysis. The mechanical properties of the grown crystals have been studied using Vickers microhardness tester. PMID:22079889

Suvitha, A; Murugakoothan, P

2012-02-01

392

Synthesis, growth, structural, spectroscopic and optical studies of a semiorganic NLO crystal: Zinc guanidinium phosphate  

NASA Astrophysics Data System (ADS)

The semi-organic nonlinear optical (NLO) crystal, zinc guanidinium phosphate (ZGuP) has been grown through synthesis between zinc sulphate, guanidine carbonate and orthophosphoric acid from its aqueous solution by slow solvent evaporation technique. Solubility of the synthesized material has been determined for various temperatures using water as solvent. The grown crystal has been characterized by powder X-ray diffraction to confirm the crystal structure. Investigation has been carried out to assign the vibrational frequencies of the grown crystals by Fourier transform infrared spectroscopy technique. 1H and 13C FT-NMR have been recorded to elucidate the molecular structure. The optical absorption study confirms the suitability of the crystal for device applications. The second harmonic generation (SHG) efficiency of ZGuP is found to be 1.825 times that of potassium dihydrogen phosphate (KDP). Thermal behavior of the grown crystals has been studied by thermogravimetric and differential thermal analysis. The mechanical properties of the grown crystals have been studied using Vickers microhardness tester.

Suvitha, A.; Murugakoothan, P.

2012-02-01

393

Structural, mechanical, optical, dielectric and SHG studies of undoped and urea-doped ?-glycine crystals  

NASA Astrophysics Data System (ADS)

Single crystals of undoped and urea-doped ?-glycine (gamma-glycine) were grown from aqueous solutions by slow evaporation technique. Morphological changes were noticed in ?-glycine crystals when urea was added as dopant. Single crystal X-ray diffraction (XRD) studies were carried out to find crystal structure and lattice parameters of the grown crystals. UV-Visible transmittance spectra were recorded for the samples to analyze the transparency in visible and near infrared (NIR) region and UV cut-off wavelength observed for the samples to be at 257 nm. Nonlinear optical (NLO) activity of the grown crystals was studied using a Q-switched and pulsed Nd:YAG laser and second harmonic generation (SHG) efficiency was found. Values of work hardening coefficient were determined from microhardness studies and confirmed that the grown crystals belong to the category of soft materials. Measurements on values of dielectric constant, dielectric loss, AC conductivity and activation energy of the samples were carried out to understand the electrical phenomena that are taking place in pure and urea-doped ?-glycine crystals.

Selvarajan, P.; Glorium Arulraj, J.; Perumal, S.

2010-01-01

394

Internal structure visualization and lithographic use of periodic toroidal holes in liquid crystals.  

PubMed

The formation of a large-area ordered structure by organic molecular soft building blocks is one of the most exciting interdisciplinary research areas in current materials science and nanotechnology. So far, several distinct organic building blocks--including colloids, block copolymers and surfactants--have been examined as potential materials for the creation of lithographic templates. Here, we report that perfect ordered arrays of toric focal conic domains (TFCDs) covering large areas can be formed by semi-fluorinated smectic liquid crystals. Combined with controlled geometry, that is, a microchannel, our smectic liquid-crystal system exhibits a high density of TFCDs that are arranged with remarkably high regularity. Direct visualization of the internal structure of the TFCDs clearly verified that the smectic layers were aligned normal to the side walls and parallel to the top surface, and merge with the circular profile on the bottom wall surface. Moreover, we demonstrate a new concept: smectic liquid-crystal lithography. Grown in microchannels from a mixture of liquid-crystal molecules and fluorescent particles, TFCDs of the smectic liquid crystals acted as a template, trapping particles in an ordered array. Our findings pose new theoretical challenges and potentially enable lithographic applications based on smectic liquid-crystalline materials. PMID:17934466

Yoon, Dong Ki; Choi, M C; Kim, Yun Ho; Kim, Mahn Won; Lavrentovich, Oleg D; Jung, Hee-Tae

2007-11-01

395

Development of Measurement System for Three-Dimensional Structure of Ice Crystals in Raw Beef Samples  

NASA Astrophysics Data System (ADS)

Micro-Slicer Image Processing System (MSIPS) has been developed for measuring the three-dimensional(3-D) structure and distribution of ice crystals formed in biological materials. The system has functions to reconstruct the 3-D image based on the image data of exposed cross sections obtained by multi-slicing of a frozen sample with the minimum thickness of 1?m and to display the internal structure as well as an arbitrary cross section of the sample choosing observation angles. The effects of freezing conditions on the morphology and distribl1tion of ice crystals were demonstrated quantitatively from the observations of raw beef stained by fluorescent indicator. The 3-D image of the sample demonstrated that the growth of ice columns was restricted by the intrinsic structure of muscle fibers. The proposed method provided a new tool to investigate the effects of freezing conditions on the size, morphology and distribution of ice crystals.

Do, Gab-Soo; Sagara, Yasuyuki; Tabata, Mizuho; Kudoh, Ken-Ichi; Higuchi, Toshiro

396

Ferroelectric domain structures in PZN8%PT single crystals studied by scanning force microscopy  

Microsoft Academic Search

Domain structures in unpoled PZN8%PT single-crystal (001) plates have been investigated by scanning force microscopy in the piezoresponse mode, at room temperature. Regular fingerprint structure of nonferroelastic domains with antiparallel polarization (of typical width 12?m) has been observed. Compared to domain patterns usually observed in other materials, domains are rather diffuse, with irregular domain walls. The latter are preferably oriented

M. Abplanalp; D. Barosova; P. Bridenbaugh; J Erhart; J Fousek; P Gnter; J Nosek; M ulc

2001-01-01

397

Structural and electrical transport properties of excimer (ArF)-laser-crystallized silicon carbide  

Microsoft Academic Search

The structural and electrical properties of undoped and doped microcrystalline silicon carbide (?c-SiC) thin films prepared by excimer (ArF) laser crystallization of plasma-enhanced chemical vapour deposited hydrogenated amorphous silicon carbide (a-SiC: H) have been analysed. Using transmission electron microscopy this material is shown to possess partial ?-SiC structure. Bonding configurations have also been characterized by infrared spectroscopy. It is shown

S. P. Lau; J. M. Marshall; T. E. Dyer

1995-01-01

398

Integrated design of structures, controls, and materials  

NASA Technical Reports Server (NTRS)

In this talk we shall discuss algorithms and CAD tools for the design and analysis of structures for high performance applications using advanced composite materials. An extensive mathematical theory for optimal structural (e.g., shape) design was developed over the past thirty years. Aspects of this theory have been used in the design of components for hypersonic vehicles and thermal diffusion systems based on homogeneous materials. Enhancement of the design methods to include optimization of the microstructure of the component is a significant innovation which can lead to major enhancements in component performance. Our work is focused on the adaptation of existing theories of optimal structural design (e.g., optimal shape design) to treat the design of structures using advanced composite materials (e.g., fiber reinforced, resin matrix materials). In this talk we shall discuss models and algorithms for the design of simple structures from composite materials, focussing on a problem in thermal management. We shall also discuss methods for the integration of active structural controls into the design process.

Blankenship, G. L.

1994-01-01

399

Silicon dioxide nanoporous structure with liquid crystal for optical sensors  

NASA Astrophysics Data System (ADS)

It has been studied the spectral characteristics of the porous silicon dioxide and cholesteric liquid crystal. It has been shown that doping of the EE1 cholesteric liquid crystal with Fe3O4 magnetite nanoparticles doesn't shift significantly the position of the transmittance minimum of the material. It has been found that the deformation of chiral pitch of cholesteric liquid crystal with magnetite is observed in case of doping of porous nanocomposite host with following shifting of minimum of transmittance into short wavelength direction. It has been shown that influence of carbon monoxide on optical characteristics of the cholesteric liquid crystal with magnetite can be explained by the interaction of CARBON MONOXIDE molecules with magnetite nanodopants.

Sushynskyi, Orest; Vistak, Maria; Gotra, Zenon; Fechan, Andriy; Mikityuk, Zinoviy

2013-05-01

400

Optimal modeling of atomic fluctuations in protein crystal structures for weak crystal contact interactions  

NASA Astrophysics Data System (ADS)

The accurate modeling of protein dynamics in crystalline states holds keys to the understanding of protein dynamics relevant to functions. In this study, we used coarse-grained elastic network models (ENMs) to explore the atomic fluctuations of a protein structure that interacts with its crystalline environment, and evaluated the modeling results using the anisotropic displacement parameters (ADPs) obtained from x-ray crystallography. To ensure the robustness of modeling results, we used three ENM schemes for assigning force constant combined with three boundary conditions for treating the crystalline environment. To explore the role of crystal contact interactions in the modeling of ADPs, we varied the strength of interactions between a protein structure and its environment. For a list of 83 high-resolution crystal structures, we found that the optimal modeling of ADPs, as assessed by a variety of metrics, is achieved for weak protein-environment interactions (compared to the interactions within a protein structure). As a result, the ADPs are dominated by contributions from rigid-body motions of the entire protein structure, and the internal protein dynamics is only weakly perturbed by crystal packing. Our finding of weak crystal contact interactions is also corroborated by the calculations of residue-residue contact energy within a protein structure and between protein molecules using a statistical potential.

Hafner, Jeffrey; Zheng, Wenjun

2010-01-01

401

Dislocation-based crystal plasticity finite element modelling of polycrystalline material deformation  

NASA Astrophysics Data System (ADS)

The objective of this research is to develop an understanding of the mechanical behavior and dislocation microstructure evolution of copper single and polycrystals, and to delineate the physical and mechanical origins of spatially-localized plastic deformation. Traditional approaches to the study of plastic instabilities have either been based on kinematic considerations, such as finite strain effects and geometric softening, or physics-based concepts. In this study, we develop a framework that combines both approaches. A rate-independent crystal plasticity model was developed to incorporate micromechanics, crystallinity and microstructure into a continuum description of finite strain plasticity. A comprehensive dislocation density model based on rate theory is employed to determine the strain hardening behavior within each plastic slip system for the fcc crystal structure. Finite strain effects and the kinematics of crystal plasticity are coupled with the dislocation-density based model via the hardening matrix in crystal plasticity. ABAQUS/CAE is employed as a finite element method solver, and several user's subroutines were developed to model fcc crystals with 2 and 12 slip systems. The developed material models are applied to study single and polycrystal deformation behavior of copper. Interfaces between the ABAQUS user's subroutine Umat and the ABAQUS main code are developed to allow further extension of the current method. The results of the model are first compared to earlier simulations of localized shear bands in a single copper crystal showing the association of the shear band with defects, as illustrated by Asaro. Current simulations for bicrystals indicate that shear band localization initiates at the triple point junction between the two crystals and the free surface. Simulations carried out for polycrystals clearly illustrate the heterogeneous nature of plastic strain, and the corresponding spatial heterogeneity of the mobile dislocation density. The origins of the spatial heterogeneities are essentially geometric, as a result of constraints on grain rotation (finite strain effects), geometric softening due to plastic, unloading of neighboring crystals. The physical origins of plastic instabilities manifest themselves in the coupling between the dislocation densities and the localized kinematically-induced softening.

Liu, Chunlei

402

The Crystal Structure of YB4.  

National Technical Information Service (NTIS)

A structure determination of YB4 was carried out in order to determine the boron positions in metal tetraborides. The structure proposed by earlier workers using the ThB4 was confirmed; however, significant departures in occupany of boron positions were n...

R. F. Giese V. I. Matkovich J. Economy

1965-01-01

403

Formation and crystal structure of metallic inclusions in a HPHT as-grown diamond single crystal  

NASA Astrophysics Data System (ADS)

One of the most important characteristics associated with crystal growth technology is the entrapment of inclusions by the growing crystal. Diamond single crystals prepared under high temperature-high pressure (HPHT) usually contain metallic inclusions. In the present paper, metallic inclusions in a diamond grown from a Fe-Ni-C system using the HPHT method have been, for the first time, systematically examined by transmission electron microscopy (TEM). Energy dispersive X-ray spectrometry (EDS) , combined with selected area electron diffraction (SAD) patterns, has been used to identify the chemical composition and crystal structure of the metallic inclusions. The metallic inclusions were found to be composed mainly of cubic ?-(FeNi), face-centered cubic (FeNi)23C6, ortho-rhombic Fe3C and hexagonal Ni3C, which may have been formed through the entrapment of molten catalyst by the growth front or through reaction of the trapped melt with contaminants in the diamond.

Yin, L.-W.; Wang, N.-W.; Zou, Z.-D.; Li, M.-S.; Sun, D.-S.; Zheng, P.-Z.; Yao, Z.-Y.

404

Crystal structure of simple metals at high pressures  

SciTech Connect

The effects of pressure on the crystal structure of simple (or sp-) elements are analysed in terms of changes in coordination number, packing density, and interatomic distances, and general rules are established. In the polyvalent elements from groups 14-17, the covalently bonded structures tend to transform to metallic phases with a gradual increase in coordination number and packing density, a behaviour normally expected under pressure. Group 1 and 2 metallic elements, however, show a reverse trend towards structures with low packing density due to intricate changes in their electronic structure. Complex crystal structures such as host-guest and incommensurately modulated structures found in these elements are given special attention in this review in an attempt to determine their role in the observed phase-transition sequences.

Degtyareva, Olga (Edinburgh)

2010-10-22

405

Solgel hydrothermal synthesis of strontium hexaferrite nanoparticles and the relation between their crystal structure and high coercivity properties  

Microsoft Academic Search

Hard magnetic strontium hexaferrite SrFe12O19 nanoparticles were synthesized by the solgel hydrothermal method. The factors affecting the synthesized process, such as the mole proportion of the reactants, pH, temperature, the hydrothermal conditions and the calcination process, have been investigated. The crystal structures of these materials were refined by Rietveld method. The obtained materials have single crystal phase, equal nano-size, plate

Thi Minh Hue Dang; Viet Dung Trinh; Doan Huan Bui; Manh Huong Phan; Dang Chinh Huynh

2012-01-01

406

Crystal structure tuning in GaAs nanowires using HCl.  

PubMed

The use of HCl during growth of nanowires presents new possibilities for controlling the growth dynamics and resulting nanowire properties. In this paper, we investigate the effects of in situ HCl on the growth of Au-seeded GaAs nanowires in a growth regime where both wurtzite and zinc blende crystal structures are possible to achieve. We find that HCl changes the crystal structure of the nanowires from pure wurtzite to defect-free zinc blende. By comparing the growth of wurtzite-zinc blende heterostructures with and without the addition of HCl, it is deduced that HCl mainly interacts with Ga species prior incorporation, reducing the amount of Ga available to contribute to the growth. We conclude that the change in crystal structure is related to the reduction of Ga adatoms, and demonstrate the realization of wurtzite-zinc blende heterostructures with atomically sharp interfaces achieved only by adding HCl. PMID:24931099

Jacobsson, Daniel; Lehmann, Sebastian; Dick, Kimberly A

2014-06-26

407

Compact Couplers for Photonic Crystal Laser-Driven Accelerator Structures  

SciTech Connect

Photonic crystal waveguides are promising candidates for laser-driven accelerator structures because of their ability to confine a speed-of-light mode in an all-dielectric structure. Because of the difference between the group velocity of the waveguide mode and the particle bunch velocity, fields must be coupled into the accelerating waveguide at frequent intervals. Therefore efficient, compact couplers are critical to overall accelerator efficiency. We present designs and simulations of high-efficiency coupling to the accelerating mode in a three-dimensional photonic crystal waveguide from a waveguide adjoining it at 90{sup o}. We discuss details of the computation and the resulting transmission. We include some background on the accelerator structure and photonic crystal-based optical acceleration in general.

Cowan, Benjamin; /Tech-X, Boulder; Lin, M.C.; /Tech-X, Boulder; Schwartz, Brian; /Tech-X, Boulder; Byer, Robert; /Stanford U., Phys. Dept.; McGuinness, Christopher; /Stanford U., Phys. Dept.; Colby, Eric; /SLAC; England, Robert; /SLAC; Noble, Robert; /SLAC; Spencer, James; /SLAC

2012-07-02

408

Crystal structures of gold, silver, and sodium chalcogenides: Sphenoidal interpretation  

SciTech Connect

The crystal structures of 13 chalcogenides of Na, Au(I), and Ag(I) in the Na{sub 2-n}(Au,Ag){sub n}(S,Se,Te) series, where 0 {<=} n {<=} 2, are interpreted from unified positions based on the sphenoidal representation. Its essence is in the consideration of the entire crystal space (with packing X atoms in the framework of close-packing, body-centered, or hybrid schemes) as a set of elementary space units (sphenoids). Unified one-dimensional associates of sphenoids, the so-called basic rods, with sets of possible atomic positions in them are selected for all structures. The mutual effect of the dimensional and stoichiometric ratios of all components on the features of filling rod positions is analyzed. New possibilities in the crystallochemical and crystal-geometry analysis of inorganic compounds whose structures are characterized by a relatively uniform distribution of atoms are demonstrated by the example of chalcogenides.

Bakakin, V. V., E-mail: bakakin@niic.nsc.ru [Russian Academy of Sciences, Institute of Inorganic Chemistry, Siberian Branch (Russian Federation)

2011-11-15

409

Computational Models for Crystal Growth of Radiation Detector Materials: Growth of CZT by the EDG Method  

SciTech Connect

Crystals are the central materials element of most gamma radiation detection systems, yet there remains surprisingly little fundamental understanding about how these crystals grow, how growth conditions affect crystal properties, and, ultimately, how detector performance is affected. Without this understanding, the prospect for significant materials improvement, i.e., growing larger crystals with superior quality and at a lower cost, remains a difficult and expensive exercise involving exhaustive trial-and-error experimentation in the laboratory. Thus, the overall goal of this research is to develop and apply computational modeling to better understand the processes used to grow bulk crystals employed in radiation detectors. Specifically, the work discussed here aims at understanding the growth of cadmium zinc telluride (CZT), a material of long interest to the detector community. We consider the growth of CZT via gradient freeze processes in electrodynamic multi-zone furnaces and show how crucible mounting and design are predicted to affect conditions for crystal growth. (authors)

Derby, Jeffrey J.; Gasperino, David [Department of Chemical Engineering and Materials Science, University of Minnesota, Minneapolis, Minnesota 55455-0132 (United States)

2008-07-01

410

Structure and local structure of perovskite based materials  

Microsoft Academic Search

Perovskites, with general formula ABX3, where A and B are cations and X is an anion, form a very important class of inorganic crystals whose physical properties are extensively used in many technological applications. The basic, so-called aristotype structure, consists of an infinite array of corner-linked anion octahedra, with the A cations in the spaces between the octahedra and a

Marta Dacil Rossell Abrodos

2006-01-01

411

Structural Order in Liquids Induced by Interfaces with Crystals  

Microsoft Academic Search

Interfaces between solids and liquids are important for a range of materials processes, including soldering and brazing, liquid-phase sintering, crystal growth, and lubrication. There is a wealth of fundamental studies on solid-liquid interfaces in materials, primarily focused on thermodynamics (relative interface energies and segregation effects) from high-temperature wetting experiments, which is often applied to processing design. Less is known about

Wayne D. Kaplan; Yaron Kauffmann

2006-01-01

412

Magnetic and crystal structure of copper(II) fluoride  

Microsoft Academic Search

A powder sample of the monoclinic, weak ferromagnet CuF2 was investigated by neutron diffraction. Using the profile method, the crystal structure was refined and the spin configuration determined. The layer type structure with planar quadratic fluorine coordination of Cu2+ (3d9) and the magnetic structure are remarkably similar to those of AgF2. The spin configuration is however different from the magnetic

P. Fischer; W. Hlg; D. Schwarzenbach; H. Gamsjger

1974-01-01

413

Local structure study of new thermoelectric materials  

NASA Astrophysics Data System (ADS)

The atomic pair distribution function (PDF) technique is used to study the local structure of new thermoelectric materials. The PDF is obtained via Fourier transformation of powder total scattering data including the important local structural information in the diffuse scattering intensities underneath, and in-between, the Bragg peaks. Having long been used to study liquids and amorphous materials, the PDF technique has been recently successfully applied to highly crystalline materials owing to the advances in modern X-ray and neutron sources and computing power. Devices based on the thermoelectric effect hold promise for solid-state cooling and power generation but developments in materials properties are required for widespread application. Recently, the importance of nanometer-scale structures has been recognized for improving the thermoelectric properties of materials. In this work we couple the power of the PDF method for giving nano-scale structural information with the need to characterize nanostructure in a number of promising novel thermoelectric materials. Promising Nanoclusters are found to exist in the PbTe based materials with unusual thermoelectric properties. For two series of material AgPb mSbTem+2 and (PbTe)1- x(PbS)x we verify the bulk nature of such nanoclusters and also determine the average chemical composition and nature of these nanoclusters. Traces of nanoclusters are also found in Ag 1-xSnSb1+xTe 3 series materials. This information is important in the effort to understand the relationship between the existence of nanoclusters and the exceptional thermoelectric properties.

Lin, He

414

The Influence of Reduced Gravity on the Crystal Growth of Electronic Materials  

NASA Technical Reports Server (NTRS)

The imperfections in the grown crystals of electronic materials, such as compositional nonuniformity, dopant segregation and crystalline structural defects, are detrimental to the performance of the opto-electronic devices. Some of these imperfections can be attributed to effects caused by Earth gravity during crystal growth process and four areas have been identified as the uniqueness of material processing in reduced gravity environment. The significant results of early flight experiments, i.e. prior to space shuttle era, are briefly reviewed followed by an elaborated review on the recent flight experiments conducted on shuttle missions. The results are presented for two major growth methods of electronic materials: melt and vapor growth. The use of an applied magnetic field in the melt growth of electrically conductive melts on Earth to simulate the conditions of reduced gravity has been investigated and it is believed that the superimposed effect of moderate magnetic fields and the reduced gravity environment of space can result in reduction of convective intensities to the extent unreachable by the exclusive use of magnet on Earth or space processing. In the Discussions section each of the significant results of the flight experiments is attributed to one of the four effects of reduced gravity and the unresolved problems on the measured mass fluxes in some of the vapor transport flight experiments are discussed.

Su, Ching-Hua; Gillies, D. C.; Szofran, F. R.; Watring, D. A.; Lehoczky, S. L.

1996-01-01

415

The Crystal Structure of GXGD Membrane Protease FlaK  

SciTech Connect

The GXGD proteases are polytopic membrane proteins with catalytic activities against membrane-spanning substrates that require a pair of aspartyl residues. Representative members of the family include preflagellin peptidase, type 4 prepilin peptidase, presenilin and signal peptide peptidase. Many GXGD proteases are important in medicine. For example, type 4 prepilin peptidase may contribute to bacterial pathogenesis, and mutations in presenilin are associated with Alzheimer's disease. As yet, there is no atomic-resolution structure in this protease family. Here we report the crystal structure of FlaK, a preflagellin peptidase from Methanococcus maripaludis, solved at 3.6 {angstrom} resolution. The structure contains six transmembrane helices. The GXGD motif and a short transmembrane helix, helix 4, are positioned at the centre, surrounded by other transmembrane helices. The crystal structure indicates that the protease must undergo conformational changes to bring the GXGD motif and a second essential aspartyl residue from transmembrane helix 1 into close proximity for catalysis. A comparison of the crystal structure with models of presenilin derived from biochemical analysis reveals three common transmembrane segments that are similarly arranged around the active site. This observation reinforces the idea that the prokaryotic and human proteases are evolutionarily related. The crystal structure presented here provides a framework for understanding the mechanism of the GXGD proteases, and may facilitate the rational design of inhibitors that target specific members of the family.

J Hu; Y Xue; S Lee; Y Ha

2011-12-31

416

The crystal structure of GXGD membrane protease FlaK  

SciTech Connect

The GXGD proteases are polytopic membrane proteins with catalytic activities against membrane-spanning substrates that require a pair of aspartyl residues. Representative members of the family include preflagellin peptidase, type 4 prepilin peptidase, presenilin and signal peptide peptidase. Many GXGD proteases are important in medicine. For example, type 4 prepilin peptidase may contribute to bacterial pathogenesis, and mutations in presenilin are associated with Alzheimer's disease. As yet, there is no atomic-resolution structure in this protease family. Here we report the crystal structure of FlaK, a preflagellin peptidase from Methanococcus maripaludis, solved at 3.6 {angstrom} resolution. The structure contains six transmembrane helices. The GXGD motif and a short transmembrane helix, helix 4, are positioned at the centre, surrounded by other transmembrane helices. The crystal structure indicates that the protease must undergo conformational changes to bring the GXGD motif and a second essential aspartyl residue from transmembrane helix 1 into close proximity for catalysis. A comparison of the crystal structure with models of presenilin derived from biochemical analysis reveals three common transmembrane segments that are similarly arranged around the active site. This observation reinforces the idea that the prokaryotic and human proteases are evolutionarily related. The crystal structure presented here provides a framework for understanding the mechanism of the GXGD proteases, and may facilitate the rational design of inhibitors that target specific members of the family.

Hu, Jian; Xue, Yi; Lee, Sangwon; Ha, Ya (Yale-MED)

2011-09-20

417

Complementary shapes in columnar liquid crystals: Structural control in homo- and heteronuclear bimetallic assemblies  

SciTech Connect

A comprehensive study of the liquid-crystalline properties of 51 bimetallic compounds based upon 1,3,5-triketonate and 1,3,5,7-tetraketonate ligands is reported. These materials are liquid crystalline when six or more side chains are appended to the mesogenic core, and only columnar phases were observed. Most of the liquid crystals were homonuclear dicopper complexes. Schiff-base derivatives of some of the triketones allowed for the synthesis of heteronuclear bimetallic liquid crystals. The NiCu and NiPd Schiff-base complexes are the first heteronuclear liquid crystals with proximate (strongly interacting) metal centers. Other heteronuclear complexes investigated were not liquid crystalline due to the tendency to retain coordinated solvent or to form strongly associated structures in the absence of axial ligands. The use of complementary shapes was demonstrated as a means to generate average relative organizations (correlations) between the complexes. The presence of these correlated structures was shown through comparisons of the structures, phase behavior, and the immiscibility between materials having the same phase but different shapes. Correlated structures were shown which produce average rotations of 90{degrees} and 180{degrees} between nearest-neighbor molecules. A crystal structure of one compound confirmed that a similar superstructure was exhibited in the solid state. In addition, it was found that the correlated structures exhibit relatively short (3.29 {angstrom}) correlations between the mesogens, thereby allowing for strong intermolecular interactions. The ability to control the orientation and relative position of transition metal centers in liquid crystals has applications in the design of new liquid-crystalline materials with useful magnetic and electronic properties. 32 refs., 8 figs., 8 tabs.

Serrette, A.G.; Lai, C.K.; Swager, T.M. [Univ. of Pennsylvania, Philadelphia, PA (United States)

1994-12-01

418

Structural determination of a partially hemihedrally twinned actin crystal.  

PubMed

An orthorhombic actin crystal (space group P2(1)2(1)2(1), unit-cell parameters a = 101.6, b = 103.0, c = 127.0 angstroms) was converted into a partially hemihedrally twinned tetragonal crystal (space group P4(3), unit-cell parameters a = b = 101.5, c = 104.2 angstroms) by induced condensation. This condensation (decrease in the c axis) was caused by the flash-freezing of the crystal, with 30% PEG 400 as a cryoprotectant, prior to data collection. Diffraction data for the twinned tetragonal crystal were collected at 100 K to 3.0 angstroms resolution (99.8% completeness with an Rsym of 8.1%) using synchrotron radiation. The hemihedral twinning of the data was observed by self-rotation function analysis and was determined to have a partial twin fraction of 0.376 from intensity statistics. The structure, with two actin molecules in the crystallographic asymmetric unit, was determined by molecular-replacement methods and refined to an R factor of 0.193. As a consequence of the crystal lattice transformation from the orthorhombic P2(1)2(1)2(1) to the tetragonal P4(3) space group, actin-actin contacts were rearranged and an inter-actin dimer disulfide bond (Cys374) observed in the orthorhombic crystal form was broken in the tetragonal crystal form. PMID:15159563

Govindasamy, Lakshmanan; Reutzel, Robbie; Agbandje-McKenna, Mavis; McKenna, Robert

2004-06-01

419

Utilization of Protein Crystal Structures in Industry  

NASA Astrophysics Data System (ADS)

In industry, protein crystallography is used in mainly two technologies. One is structure-based drug design, and the other is structure-based enzyme engineering. Some successful cases together with recent advances are presented in this article. The cases include the development of an anti-influenza drug, and the introduction of engineered acid phosphatase to the manufacturing process of nucleotides used as umami seasoning.

Ishikawa, Kohki

420

Synthesis of Two-Photon Materials and Two-Photon Liquid Crystals  

NASA Technical Reports Server (NTRS)

The duration of the grant was interrupted by two major accidents that the PI met with-- an auto accident in Pasadena, CA during her second summer at JPL which took almost eight months for recovery and a second accident during Fall 2000 that left her in crutches for the entire semester. Further, the time released agreed by the University was not given in a timely fashion. The candidate has been given post-grant expire time off. In spite of all