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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 1,513 records · Page 84
All sourcesNASA NTRSDOE OSTI
DOE OSTI2016

Dimorphism of RF{sub 3} (R = La–Nd) crystals based on the data of X-ray diffraction studies

The ratio of two forms of tysonite in nominally pure single crystals of RF{sub 3} (R = La–Nd) obtained from melts under identical conditions (the as-grown state) is studied for the first time by X-ray diffraction. Crystals of RF{sub 3} with R = La–Nd belong to the β-LaF{sub 3} structural type (space group P3̄c1, Z = 6) and form twins. Samples 0.2–0.4 in diameter contain inclusions of the high-temperature a form (space group P6{sub 3}/mmc, Z = 2). It is shown that twinning and dimorphism of the RF{sub 3} crystals (R = La–Nd) have a common structural basis.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2016

X-ray diffraction study of Ba{sub 3}TaFe{sub 3}Si{sub 2}O{sub 14} single crystal—a promising langasite-type multiferroic

Ba{sub 3}TaFe{sub 3}Si{sub 2}O{sub 14} single crystals (sp. gr. P321, Z = 1), promising langasite-type multiferroics, have been grown by floating zone melting. An accurate X-ray diffraction study of Ba{sub 3}TaFe{sub 3}Si{sub 2}O{sub 14} single crystal has been performed using two datasets, obtained independently for two different orientations of the same sample on a diffractometer equipped with a CCD area detector at 295 K. Structure refinement is performed based on an averaged dataset: a = 8.5355(1) Å, c = 5.2332(1) Å, sp. gr. P321, Z = 1; the R factors of model structure refinement were found to be R/wR = 1.02/1.23% for 4552 independent reflections. Disordering asymmetry is revealed for the magnetic Fe ion in the 3f site and the Ba cation in the 3e site.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2016

Structure of Cs{sub 4}(HSO{sub 4}){sub 3}(H{sub 2}PO{sub 4}) single crystals

Single crystals of Cs{sub 4}(HSO{sub 4}){sub 3}(H{sub 2}PO{sub 4}) are synthesized and studied for the first time. The new compound is found in the course of studies of the phase diagram of the CsHSO{sub 4}–CsH{sub 2}PO{sub 4}–H{sub 2}O triple system. Data on the atomic crystal structure of single-crystalline and powder specimens, as well as on structural phase transitions, are obtained.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2016

Three-dimensional structure of phosphoribosyl pyrophosphate synthetase from E. coli at 2.71 Å resolution

Phosphoribosyl pyrophosphate synthetase from Escherichia coli was cloned, purified, and crystallized. Single crystals of the enzyme were grown under microgravity. The X-ray diffraction data set was collected at the Spring-8 synchrotron facility and used to determine the three-dimensional structure of the enzyme by the molecular-replacement method at 2.71 Å resolution. The active and regulatory sites in the molecule of E. coli phosphoribosyl pyrophosphate synthetase were revealed by comparison with the homologous protein from Bacillus subtilis, the structure of which was determined in a complex with functional ligands. The conformations of polypeptide-chain fragments surrounding and composing the active and regulatory sites were shown to be identical in both proteins.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2016

Growth and structure of K{sub 2}Ni{sub x}Co{sub (1–x)}(SO{sub 4}){sub 2} · 6H{sub 2}O single crystals

Single crystals of the K{sub 2}Ni{sub x}Co{sub (1–x)}(SO{sub 4}){sub 2} · 6H{sub 2}O composition are grown by spontaneous flux crystallization. More exact chemical formulas of the single crystals are determined based on the diffraction data as K{sub 2}Co(SO{sub 4}){sub 2} · 6H{sub 2}O (I), K{sub 2}(Co{sub 0.657}Ni{sub 0.343})(SO{sub 4}){sub 2} · 6H{sub 2}O (II), K{sub 2}(Co{sub 0.226}Ni{sub 0.774})(SO{sub 4}){sub 2} · 6H{sub 2}O (III), K{sub 2}(Co{sub 0.216}Ni{sub 0.784})(SO{sub 4}){sub 2} · 6H{sub 2}O (IV), and K{sub 2}Ni(SO{sub 4}){sub 2} · 6H{sub 2}O (V). The substitution of nickel atoms for cobalt atoms in structure I results in a shortening of all (Co,Ni)–O interatomic distances. With increasing Ni concentration, the (Co,Ni)–O2 distance shortens to a lesser degree than the (Co,Ni)–O1 and (Co,Ni)–O3 distances and, as a consequence, the distortion of (Co,Ni)O{sub 6} octahedra decreases. NiO{sub 6} polyhedra are less distorted than CoO{sub 6} octahedra. The analysis of difference syntheses of electron density shows that the number of uninterpretable peaks on the maps of mixed crystals II, III, and IV, as well as on the map of K{sub 2}Co(SO{sub 4}){sub 2} · 6H{sub 2}O, is larger with respect to those of structure K{sub 2}Ni(SO{sub 4}){sub 2} · 6H{sub 2}O.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2016

Structural features of single crystals of LuB{sub 12} upon a transition to the cage-glass phase

The unit-cell parameters of dodecaboride LuB{sub 12}, which undergoes a transition to the cage-glass phase, have been determined for the first time in the temperature range of 50–75 K by X-ray diffraction, and the single-crystal structure of this compound is established at 50 K. Nonlinear changes in the unit-cell parameters correspond to anomalies in the physical properties near the glass-transition temperature T* ~ 50–70 K. This compound has cubic symmetry at room temperature, and it is reduced to tetragonal symmetry at lower temperatures. Based on the X-ray diffraction data and relying on the physical properties of the crystals, the structure model, in which a small part (~15%) of Lu atoms are displaced from the 2a sites at the centers of the B{sub 24} cuboctahedra to the 16n sites of sp. gr. I4/mmm, seems preferable.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2016

Accurate structural study of langasite-family Ca{sub 3}TaGa{sub 3}Si{sub 2}O{sub 14} crystal

An accurate X-ray diffraction study of Ca{sub 3}TaGa{sub 3}Si{sub 2}O{sub 14} single crystal has been performed using two datasets obtained on a diffractometer equipped with a CCD area detector (a = 8.1056(2) Å, c = 4.9800(1) Å, sp. gr. P321, Z = 1, R/wR = 0.486/0.488%). A model structure is determined which is characterized by a high degree of reproducibility of structural parameters. Each site in Ca{sub 3}TaGa{sub 3}Si{sub 2}O{sub 14} is occupied by atoms of only one type. Nevertheless, its structural feature is asymmetric disordering of sites of Ca, Ta, Ga, and two out of three oxygen atoms occupying special and general sites. A transition of some part of Ca atoms (~3%) from 3e sites on the twofold symmetry axis to general 6g sites is revealed.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2016

Bidomain structures formed in lithium niobate and lithium tantalate single crystals by light annealing

The bidomain structures produced by light external heating in z-cut lithium niobate and lithium tantalate single crystals are formed and studied. Interdomain regions about 200 and 40 μm wide in, respectively, LiNbO{sub 3} and LiTaO{sub 3} bidomain crystals are visualized and studied by optical microscopy and piezoresponse force microscopy. Extended chains and lines of domains in the form of thin layers with a width less than 10 μm in volume, which penetrate the interdomain region and spread over distances of up to 1 mm, are found.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2016

A facile approach towards synthesis, characterization, single crystal structure, and DFT study of 5-bromosalicylalcohol

5-Bromosalicylalcohol was prepared by the interaction of NaBH{sub 4} and 5-bromosalicylaldehyde. The use of sodium borohydride makes the reaction easy, facile, economic and does not require any toxic catalyst. The compound is characterized by FTIR, {sup 1}H NMR, {sup 13}C NMR, TEM and ESI-mass spectra. Crystal structure is determined by single crystal X-ray analysis. Quantum mechanical calculations of geometries, energies and thermodynamic parameters are carried out using density functional theory (DFT/B3LYP) method with 6-311G(d,p) basis set. The optimized geometrical parameters obtained by B3LYP method show good agreement with experimental data.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2016

Structural investigation of cooperite (PtS) crystals

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

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2016

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

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

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2016

Fluorine-ion conductivity of different technological forms of solid electrolytes R{sub 1–y}M{sub y}F{sub 3–y} (LaF{sub 3} Type ) (M = Ca, Sr, Ba; R Are Rare Earth Elements)

We have investigated the conductivity of some representatives of different technological forms of fluoride-conducting solid electrolytes R{sub 1–y}M{sub y}F{sub 3–y} (M = Ca, Sr, Ba; R are rare earth elements) with an LaF{sub 3} structure: single crystals, cold- and hot-pressing ceramics based on a charge prepared in different ways (mechanochemical synthesis, solid-phase synthesis, and fragmentation of single crystals), polycrystalline alloys, etc. It is shown (by impedance spectroscopy), that different technological forms of identical chemical composition (R, M, y) exhibit different electrical characteristics. The maximum conductivity is observed for the single-crystal form of R{sub 1–y}M{sub y}F{sub 3–y} tysonite phases, which provides (in contrast to other technological forms) the formation of true volume ion-conducting characteristics.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2016

Ordering of calcium and vacancies in calcium catapleiite CaZr[Si{sub 3}O{sub 9}] • 2H{sub 2}O

A sample of holotypic calcium catapleiite from the Burpala alkaline massif (Northern Baikal, Russia) is studied by single crystal X-ray analysis at 120 K and IR spectroscopy. The empirical formula of calcium catapleiite is Ca{sub 0.97}Na{sub 0.02}Zr{sub 1.01}Si{sub 3}O{sub 9} • 2H{sub 2}O (Z = 4). The X-ray diffraction study confirms the orthorhombic unit cell with the following parameters: a = 7.406(1), b = 12.687(1), and c = 10.112(1) Å; V = 950.1(2) Å{sup 3}; space group Pbnn. The crystal structure is refined in the anisotropic approximation of atomic displacement parameters using 1177 reflections with I > 2σ(I) to the final R = 2.91%. The structure of calcium catapleiite under study is based on the microporous heteropolyhedral framework formed by ZrO{sub 6} octahedra and threemembered silicon–oxygen rings [Si{sub 3}O{sub 9}]. It is on the whole analogous to the structures of the samples studied earlier, but differs from them by a high degree of ordering of calcium and vacancies at extraframework positions. The distribution of calcium over Ca1 and Ca2 positions in the calcium catapleiite structure leads to the formation of zigzag chains of the …Ca1–Zr–Ca1–Zr… and …Ca2–h–Ca2–□… types. Low occupancy of the Ca2 position and its alternation with the vacancy are prerequisites for potential Ca{sup 2+} cationic conduction.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2016

Crystal structure of (E)-3-fluoro-N-((5-nitrothiophen-2-yl)methylene)aniline

The structure of the title compound C{sub 11}H{sub 7}FN{sub 2}O{sub 2}S was characterized by single crystal X-ray diffraction. The compound crystallizes in the monoclinic space group P2{sub 1}/n with Z = 12, i.e. with three molecules in asymmetric unit. The molecules are not planar: the dihedral angles between the planes of thiophene and the benzene rings are 42.3(3)°, 42.0(3)°, and 48.9(2)°. In the crystal, intermolecular C–H···F interactions link the molecules through R{sub 2}{sup 2} (14) ring motif. The crystal packing is also stabilized by π···π interactions.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2016

Study of a macrodefect in a silicon carbid single crystal by means of X-ray phase contrast

The morphology of a macrodefect in a single-crystal silicon carbide wafer has been investigated by the computer simulation of an experimental X-ray phase-contrast image. A micropipe, i.e., a long cavity with a small (elliptical in the general case) cross section, in a single crystal has been considered as a macrodefect. A far-field image of micropipe has been measured with the aid of synchrotron radiation without a monochromator. The parameters of micropipe elliptical cross section are determined based on one projection in two directions: parallel and perpendicular to the X-ray beam propagation direction, when scanning along the pipe axis. The results demonstrate the efficiency of the phase contrast method supplemented with computer simulation for studying such macrodefects when the defect position in the sample volume is unknown beforehand.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2016

Crystal structure and packing analysis of nitrofurantoin N,N-dimethylformamide solvate

The N, N′-dimethylformamide solvated crystal of the drug nitrofurantoin has been prepared and analysed by single-crystal X-ray diffraction. The two co-crystallized molecules, in the 1 : 1 stoichiometric ratio, are linked by a medium/strong N–H···O hydrogen bond (N···O is 2.759 (3) Å) and a weaker C–H···O interaction to form isolated supramolecular adducts, that in turn are packed into the lattice framework mainly through C–H···O hydrogen bonds. Two-dimensional fingerprint plots of Hirshfeld surfaces are used to visualize, analyze and compare intermolecular interactions found in the title compound and in similar structures.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2016

Calibration of CryojetHT and Cobra Plus Cryosystems used in X-ray diffraction studies

CryoJetHT (Oxford Instruments) and Cobra Plus (Oxford Cryosystems) cryosystems, which are used for sample cooling in X-ray diffraction experiments, have been calibrated. It is shown that the real temperature in the vicinity of the sample differs significantly (the deviation is as high as 8–10 K at low temperatures) from the temperature recorded by authorized sensors of these systems. The calibration results are confirmed by measurements of the unit-cell parameters of GdFe{sub 3}(BO{sub 3}){sub 4} single crystal in the temperature range of its phase transition. It is shown that, to determine the real temperature of a sample, one must perform an independent calibration of cryosystems rather than rely on their ratings.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2016

Production of complex rubidium and cesium hydrogen sulfate‒phosphates

The solubility in the CsH{sub 2}PO{sub 4}‒CsHSO{sub 4}‒H{sub 2}O system at different temperatures (25, 50, and 75°C) is studied and the phase equilibria in the Rb{sub 3}H(SO{sub 4}){sub 2}‒RbH{sub 2}PO{sub 4}‒H{sub 2}O system under isothermal conditions (at 25°C) are analyzed. The temperature and concentration conditions for forming Rb{sub 2}(HSO{sub 4})(H{sub 2}PO{sub 4}), Rb{sub 4}(HSO{sub 4}){sub 3}(H{sub 2}PO{sub 4}), Cs{sub 4}(HSO{sub 4}){sub 3}(H{sub 2}PO{sub 4}), Cs{sub 3}(HSO{sub 4}){sub 2}(H{sub 2}PO{sub 4}), Cs{sub 2}(HSO{sub 4})(H{sub 2}PO{sub 4}), and Cs{sub 6}H(HSO{sub 4}){sub 3}(H{sub 2}PO{sub 4}){sub 4} compounds (the latter has been obtained for the first time) are determined. The conditions for growing large single crystals of complex acid rubidium and cesium salts are found.

36 MATERIALS SCIENCE↗