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At least 1,585 records · Page 88
All sourcesNASA NTRSDOE OSTI
DOE OSTI2018

Accurate Refinement of the Crystal Structure of Ba{sub 3}TaGa{sub 3}Si{sub 2}O{sub 14} from Langasite Family and Analysis of Structural Transformations Due to Isomorphous Cation Substitutions

An accurate structure analysis of a Ba{sub 3}TaGa{sub 3}Si{sub 2}O{sub 14} single crystal from langasite family was performed using four X-ray diffraction data sets collected on a diffractometer equipped with a CCD area detector (sp. gr. P321, Z = 1, sinθ/λ ≤ 1.35 Å{sup –1}; at 295 K a = 8.516(1) Å, c = 5.1910(6) Å, R/wR = 0.58/0.56%, Δρ{sub min}/Δρ{sub max} =–0.73/0.42 e/Å{sup 3}, 4414 independent reflections; at 106 K a = 8.5109(9) Å, c = 5.1861(9) Å, R/wR = 0.75/0.86%, Δρ{sub min}/Δρ{sub max} =–0.81/1.06 e/Å{sup 3}, 4382 reflections). The distinguishing feature of the Ba{sub 3}TaGa{sub 3}Si{sub 2}O{sub 14} structure is a strong disorder of the Ga atom at the 3f site. Structural transformations in the series of Сa{sub 3}TaGa{sub 3}Si{sub 2}O{sub 14}–Sr{sub 3}TaGa{sub 3}Si{sub 2}O{sub 14}–Ba{sub 3}TaGa{sub 3}Si{sub 2}O{sub 14}–Ba{sub 3}TaFe{sub 3}Si{sub 2}O{sub 14} crystals were analyzed.

36 MATERIALS SCIENCE↗
DOE OSTI2018

The Influence of Cation Substitution on the Kinetics of Phase Transitions in Crystals of (K,NH{sub 4}){sub 3}H(SO{sub 4}){sub 2} Solid Solutions

The structure of (K{sub 0.967}(NH{sub 4}){sub 0.033}){sub 3}H(SO{sub 4}){sub 2} crystals, belonging to the K{sub 3}H(SO{sub 4}){sub 2}–(NH{sub 4}){sub 3}H(SO{sub 4}){sub 2}–H{sub 2}O salt system, has been investigated by X-ray structural analysis. The room-temperature characteristics of the atomic structure of these crystals are found to be as follows: sp. gr. C2/c, Z = 4, a = 14.7025(4) Å, b = 5.6859(2) Å, c = 9.7885(3) Å, and R/wR = 0.021/0.030%. The thermal and optical properties of (K,NH{sub 4}){sub 3}H(SO{sub 4}){sub 2} and K{sub 3}H(SO{sub 4}){sub 2} single crystals have been investigated and compared in a temperature range of 295–500 K.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2018

Structural Conditionality of the Ionic Conductivity of MTiORO{sub 4} (M = K, Rb; R = P, As) Single Crystals

The ionic conductivity σ{sub ||c} along the crystallographic axis c and the structural imperfection of the lattices of KTiOPO{sub 4}, RbTiOPO{sub 4}, and RbTiOAsO{sub 4} single crystals with low defect concentration, grown by the high temperature solution growth technique, have been investigated by impedance spectroscopy and X-ray diffraction analysis. Isomorphic substitutions of Rb{sup +} ions for conduction K{sup +} cations in MTiOPO{sub 4} crystals decreases the σ{sub ||c} value, whereas the substitution of As{sup 5+} ions for framework P{sup 5+} cations in RbTiORO{sub 4} crystals increases the σ{sub ||c} value. The σ{sub ||c} values at 573 K are found to be 1.0 × 10{sup –5}, 5.7 × 10{sup –6}, 2.0 × 10{sup –6}, and 3.3 × 10{sup –5} S/cm for the KTiOPO{sub 4}, RbTiOPO{sub 4} {100}, RbTiOPO{sub 4} {201}, and RbTiOAsO{sub 4} crystals, respectively (the growth zone of the crystalline boule from which the samples were cut is indicated in braces).

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2018

Structure of Nd{sub 5}Mo{sub 3}O{sub 16+δ} Single Crystals Doped with Tungsten

The structure of tungsten-doped Nd{sub 5}Mo{sub 3}O{sub 16+δ} single crystals has been investigated by X-ray diffraction analysis, energy-dispersive X-ray spectroscopy (EDXS) microanalysis, and extended X-ray absorption fine-structure (EXAFS) spectroscopy. Tungsten atom, which partially replaces molybdenum atoms in the structure, is found to be located close (at a distance of 0.57 Å) to the Mo atom site. The interstitial oxygen atom О3 shifts from the crystallographic site with coordinates (0.5, 0.5, 0) to the site with coordinates (0.43, 0.48, 0.04) and complements the tungsten coordination to octahedral. The decrease in the unit-cell parameter and conductivity with an increase in the tungsten concentration in the sample is shown to be related to the fact that the interstitial oxygen atom О3 (responsible for conductivity) is in the coordination environment of tungsten atom.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Absolute Configuration of Andrographolide and Its Proliferation of Osteoblast Cell Lines

Andrographolide, C{sub 20}H{sub 30}O{sub 5}, is a labdane diterpenoid which was isolated from the leave of Andrographis paniculata. Its crystal structure is determined by single crystal X-ray diffraction: monoclinic, sp. gr. P2{sub 1}, Z = 2. Absolute configuration is determined by the refinement of the Flack parameter to 0.21(19). In the crystal, molecules are linked by O–H···O hydrogen bonds and C–H···O interactions into two dimensional network parallel to the (001) plane. Its proliferation of osteoblast cell lines is reported.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2018

X-Ray Structure Investigation of Sr{sub 3}NbGa{sub 3}Si{sub 2}O{sub 14} Langasite Family Crystal

An accurate structure analysis of Sr{sub 3}NbGa{sub 3}Si{sub 2}O{sub 14} single crystals, belonging to the langasite family, has been performed. Two datasets are obtained on an Xcalibur S diffractometer equipped with a CCD detector. The structure is been refined using an averaged dataset: sp. gr. P 321, Z = 1, 295 K, sin θ/λ ≤ 1.35 Å{sup –1}, a = 8.2797(3) Å, c = 5.0774(5) Å; the agreement factors between the model and experiment are found to be R/wR = 0.76/0.64% and Δρ{sub min}/Δρ{sub max} =–0.21/0.17 e/Å{sup 3} for 3820 independent ref lections. The Sr{sub 3}NbGa{sub 3}Si{sub 2}O{sub 14} and Sr{sub 3}NbFe{sub 3}Si{sub 2}O{sub 14} structures are compared, and the role of magnetic ions in the predicted P321 → P3 phase transition is analyzed.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2018

Synthesis, Structure, and Band Gap of a Novel Inorganic–Organic Hybrid Material Based on Antimony Halide and Organoamine

Using an organoamine, 2,5-bis (1-imidazoly) pyridine (L), a novel inorganic-organic hybrid material based on antimony halide formulated as {(CH_3)_2L}{sup 2+}{(Sb_4Cl_8I_8)"0"."5}{sup 2–}(1) was synthesized in situ via solvothermal technique and characterized by the single-crystal X-ray diffraction. During the synthesis, the organoamine L was transformed in situ into the imidazolium ion, {(CH_3)_2L}{sup 2+}. In the compound 1, four Sb(III) ions are linked by two u{sub 3{sup −}}I{sup –} and four uu{sub 2{sup −}}I{sup –} ligands into a (Sb{sub 4}I{sub 8}Cl{sub 8}){sup 4–}unit, in which eight Cl{sup –}ions and two I{sup –}ions act as the terminal ligands. The uncoordinated {(CH_3)_2L}{sup 2+} organoamine moieties are linked with the (Sb{sub 4}I{sub 8}Cl{sub 8}){sup 4–} clusters via H bonds into three-dimensional (3D) supramolecular architecture. The band structure calculation shows that the compound has an indirect band gap of 2.253 eV.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Molecular and Crystal Structure of 2-{(E)-[(5-Chloro-2-methoxyphenyl)imino]methyl}-4-nitrophenol

The molecular structure of the title compound, C{sub 14}H{sub 11}ClN{sub 2}O{sub 4}, was determined by single crystal X-ray diffraction. The compound crystallizes in the monoclinic sp. gr. P2{sub 1}/c with Z = 4. The title compound, C{sub 14}H{sub 11}ClN{sub 2}O{sub 4}, is a Schiff base which adopts the phenol-imine tautomeric form in the solid state.The molecule is almost planar and the dihedral angle between the planes of two aromatic ring is 2.2(1)°. The molecular structure is stabilized by intramolecular O–H···N hydrogen bond which generates a six-membered ring. In the crystal structure, the molecules are linked together by intermolecular C–H···O interactions.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2018

Crystal Structure of 2-((E)-(5-Bromo-2- hydroxybenzylidene)hydrazono)-1,2-diphenylethanone

The molecular structure of the title compound, C{sub 21}H{sub 15}Br{sub 1}N{sub 2}O{sub 2}, was characterized by single crystal X-ray diffraction. The compound crystallizes in the triclinic sp. gr. P1̄ with Z = 2. The molecule is not planar: the dihedral angle between the planes of two aromatic rings [C1/C6] and [C16/C21] is 84.9(2)°. The other dihedral angle between two aromatic rings [C9/C14] and [C16/C21] is 88.8(2)°. The title compound exists as a phenol-imine tautomer, in which a strong intramolecular O–H···N hydrogen bond is formed. This study verifies the preference of the phenol-imine tautomeric form in the solid state. A π–π stacking interactions are also observed, which may influence crystal stability: the distance between centroids is 3.702(2) Å.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Peculiarities of the Structure, Moduli of Elasticity, and Knoop Indentation Patterns of Deformation and Fracture of Single Crystals of Potassium, Rubidium, Cesium, and Ammonium Hydrophthalates

The crystal structure of potassium, rubidium, cesium, and ammonium hydrophthalates is analyzed based on the data in the literature. A relationship between their structure and elastic and mechanical properties has been established for the first time. Young’s moduli, shear moduli, and Poisson’s ratios in the (100), (010), and (001) planes of these crystals are calculated, and Knoop indentation of these planes is performed. Anisotropy of the elastic and mechanical properties of the crystals is revealed. Rubidium, cesium, and ammonium hydrophthalates are found to be partial auxetics. Ammonium hydrophthalate, whose structure contains additional (as compared with other hydrophthalates) hydrogen bonds, exhibits the highest anisotropy of properties.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Synthesis, Crystal Structure, Antioxidant, and α-Glucosidase Inhibitory Activities of Methoxy-substituted Benzohydrazide Derivatives

Eight methoxy substituted at the benzylidene moiety benzohydrazide derivatives [R = 2-OCH{sub 3} (1), 3-OCH{sub 3} (2), 4-OCH{sub 3} (3), 2,3-(OCH{sub 3}){sub 2} (4), 3,4-(OCH{sub 3}){sub 2} (5), 2,4,5-(OCH{sub 3}){sub 3} (6), 2,4,6-(OCH{sub 3}){sub 3} (7), and 3,4,5-(OCH{sub 3}){sub 3} (8)] were synthesized and characterized by {sup 1}H NMR, FT-IR and UV-Vis spectroscopy. The crystal structure of 4 was determined by single crystal X-ray diffraction (sp. gr. Pbca, Z = 8). The molecule is slightly twisted with the dihedral angle between the two phenyl rings being 9.33(14)°. The methoxy group at the ortho position is twisted [C–O–C–C angle is–109.2(3)°] whereas the other at meta position is co-planar with the attached benzene ring. In the crystal packing, the molecules are linked into two-dimensional network parallel to the (001) plane by O–H···O, O–H···N, and N–H···O hydrogen bonds. Compounds 1–8 were evaluated for an antioxidant and α-glucosidase inhibitory activities and the results suggested that the −OCH{sub 3} substituent was ineffective for bioactivity enhancement.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2018

Increase in the Fluorine-Ion Conductivity of Single Crystals of Tysonite-type CeF{sub 3} Superionic Conductor by Substituting Polarized Cd{sup 2+} Ions for Ce{sup 3+} Ions

The fluorine-ion conductivity of single crystals with a tysonite (LaF{sub 3}) structure with heterovalent isomorphic substitutions of highly polarizable Cd{sup 2+} cations with a 18-electron shell for rare earth ions Ce{sup 3+} have been studied for the first time. Ce{sub 0.995}Cd{sub 0.005}F{sub 2.995} single crystals have been grown from melt by the Bridgman technique in a fluorinating atmosphere. The fluorine-ion conductivity of single crystal is measured by impedance spectroscopy in the temperature range from 153 to 1073 K, where it increases by a factor of 10{sup 9}, approaching the value σ{sub dc} = 5 × 10{sup –2} S/cm at 1073 K. At T{sub 0} = 450 ± 20 K, the dependence σ{sub dc}(T) is split into two portions with the ion-transport activation enthalpy ΔH{sub σ} = 0.39 ± 0.01 eV (T < T{sub 0}) and ΔH{sub σ} = 0.23 ± 0.02 eV (T > T0). It is found that at T = 293 K the conductivity σ{sub dc} = 3 × 10{sup –5} S/cm of Ce{sub 0.995}Cd{sub 0.005}F{sub 2.995} crystal is higher by a factor of 10 than the conductivity of the tysonite matrix CeF{sub 3} and close to the σ{sub dc} value for Ce{sub 0.995}Sr{sub 0.005}F{sub 2.995} crystal. This finding indicates a significant effect of the substitutions of Cd{sup 2+} ions for Ce{sup 3+} on the σdc value and the advantage of Cd{sup 2+} ions over Ca{sup 2+} and Ba{sup 2+} from the viewpoint of increasing σ{sub dc}.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2018

Electrical Conductivity of Cancrinite-Type Na{sub 8−2x}Ca{sub x}[Al{sub 6}Si{sub 6}O{sub 24}][CO{sub 3}] · 2H{sub 2}O (x ≤ 0.03) Crystals

The electrical conductivity of crystals of artificial cancrinite Na{sub 8−2x}Ca{sub x}[Al{sub 6}Si{sub 6}O{sub 24}][CO{sub 3}] · 2H{sub 2}O (x ≤ 0.03) has been studied in the temperature range of 498−604 K. These crystals were grown by hydrothermal synthesis on a seed in the Na{sub 2}O–Al{sub 2}O{sub 3}–SiO{sub 2}–H{sub 2}O system (t = 380−420°С, P = 3 × 10{sup 7}−9 × 10{sup 7} Pa). The ionic conductivity of a single-crystal sample (sp. gr. P6{sub 3}), measured along the crystallographic axis c, is low: σ = 8 × 10{sup –7} S/cm at 300°С. The electric transport activation energy is E{sub a} = 0.81 ± 0.05 eV. The relationship between the ionic conductivity and specific features of the atomic structure of cancrinites is discussed.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2018

Formation of Dislocations and Twins As a Result of Uniaxial Compression of Magnesium Single Crystals: Molecular Dynamics Simulation

An atomistic simulation of the deformation of ideal magnesium crystal along the [112̄0] crystallographic axis has been performed. The evolution of structural defects under load at T = 300–350 K is considered in detail. It is established that the nucleation of dislocations in an ideal crystal occurs when the stress reaches a level of 0.1G (G is the shear modulus). The acting deformation modes are found to be prismatic slip of a dislocations and {101̄3} twinning. The formation of dislocation networks and dislocation sites in the twinning plane is observed. Some reactions are proposed to describe the dislocation evolution in the (3̄034) plane.

36 MATERIALS SCIENCE↗
DOE OSTI2018

A Two-Dimensional Coordination Polymer Based on 1,1':4',1''-Terphenyl-2',4,4'',5'-tetracarboxylate

The coordination polymer, [MnL{sub 0.5}(H{sub 2}O)(phen)]{sub n} (H{sub 4}L = 1,1':4',1''-terphenyl-2',4,4'',5'-tetracarboxylic acid, phen = 1,10-phenanthroline), has been solvothermal synthesized and structurally characterized by single-crystal X-ray diffraction. Complex crystallizes in triclinic sp. gr.P1̄ with Z = 2. Two carboxylate oxygen atoms in the central phenyl rings from two μu{sub 6{sup −}}L{sup 4–} ligands doubly-bridge two Mn(II) ions to form the dinuclear Mn{sub 2}(O{sub COO{sup −}}){sub 2} unit. Each dinuclear Mn{sub 2}(O{sub COO{sup −}}){sub 2} unit links four L{sup 4–} ligands and each L{sup 4–}ligand bridges four dinuclear Mn{sub 2}(O{sub COO{sup −}}){sub 2} units to generate a 2D coordination network, which can be rationalized as a binodal (4,4) topological network by considering the dinuclear Mn{sub 2}(O{sub COO{sup −}}){sub 2} units and L{sup 4–} ligands as 4-connected nodes.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Thermal Expansion of EuF{sub 2+x} Single Crystals and Their Thermal Stability

Thermal expansion of an EuF{sub 2.136} nonstoichiometric crystal with the fluorite structure type (Eu{sub 0.864}{sup 2+}Eu{sub 0.136}{sup 3+}F{sub 2.136}, lattice parameter 5.82171(5) Å) has been experimentally investigated in the temperature range of 9–500 K. The coefficient of thermal expansion is α = 15.8 × 10{sup –6} K{sup –1} at T = 300 K. The observed anomalies in the behavior of the coefficient of thermal expansion at T > 400 K are related to the oxidation processes with partition of Eu{sup 2+} ions. It is established by differential scanning calorimetry that the onset temperature of EuF{sub 2+x} oxidation in air is 430 K and that this process occurs in three stages. X-ray diffraction analysis shows that the oxidation is accompanied by the formation of a phase mixture based on two modifications of the Eu{sub 1–y}{sup 3+}Eu{sub y}{sup 2+}F{sub 3–y} solid solution with the structure types of tysonite (LaF{sub 3}), orthorhombic β-YF{sub 3} phase, and europium oxyfluorides of variable composition EuO{sub 1–x}F{sub 1+2x}, with dominance of the latter.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2018

Spectrometer of Synchrotron Radiation Based on Diffraction Focusing a Divergent Beam Formed by a Compound Refractive Lens

The results of the first experimental realization of a spectrometer based on the effect of diffraction focusing of X rays by a flat single crystal are discussed. A secondary X-ray source with a relatively high angular divergence and small sizes was formed at the focus of a compound refractive lens having 50 beryllium biconcave elements with a curvature radius of 50 μm. The silicon spectrometer crystal was cut in the form of a wedge of variable thickness, oriented perpendicular to the diffraction plane. The reflection 111 was used for energies of 8.3 and 12 keV. To simulate the experiment, a computer program was developed, which takes into account accurately and for the first time the focusing of radiation by the lens and its subsequent diffraction in the crystal. A calculated curve for a monochromatic beam has made it possible to determine the monochromator spectrum with high resolution from experimental data for a polychromatic beam. It is shown that monochromator resolution increases with an increase in the distance from the compound refractive lens to the crystal.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2018

Synthesis, Characterization, Crystal Structure, and Hirshfeld Surface Analysis of Ethyl 2-(4-bromophenyl)-1-cyclohexyl-1H-benzo[d]imidazole-5-carboxylate

The title compound, C{sub 22}H{sub 23}N{sub 2}BrO{sub 2} was synthesized via one-pot reductive cyclization method and characterized by CNH analysis, FT-IR, UV-visible, mass, {sup 1}H and {sup 13}C NMR spectra, thermogravimetric analysis (TGA) and single crystal X-ray diffraction method. The compound crystallizes in monoclinic crystal system: sp. gr. P2{sub 1}/c, Z = 4. The crystal data reveals that the intermolecular interactions of the C–H···π and π···π type connect the molecules which was also visualized with the help of Hirshfeld surface analysis.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗