Pressure-induced polymorphism in nanostructured SnSe

The pressure-induced phase transitions in nanostructured SnSe were investigated using angle-dispersive X-ray diffraction in a synchrotron source along with first-principles density functional theory (DFT) calculations. The variation of the cell parameters along with enthalpy calculations for pressures up to 18 GPa have been considered. Both the experimental and the theoretical approaches demonstrate a phase transition at around 4 GPa. Below 8.2 GPa the X-ray diffraction patterns were fitted using the Rietveld method with space groupPnma(No. 62). The lattice parameters and atomic positions for the above-mentioned symmetry were used in DFT calculations of thermodynamic parameters. The enthalpy calculations with the computationally optimized structure and the proposedPnmastructure of SnSe were compatible. The variations of the cell volume for the high-pressure phases are described by a third-order Birch–Murnaghan equation of state.

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Crystal structure determination of karibibite, an Fe3+ arsenite, using electron diffraction tomography

Mineralogical Magazine ◽

10.1180/minmag.2016.080.159 ◽

2017 ◽

Vol 81 (5) ◽

pp. 1191-1202 ◽

Cited By ~ 5

Author(s):

Fernando Colombo ◽

Enrico Mugnaioli ◽

Oriol Vallcorba ◽

Alberto García ◽

Alejandro R. Goñi ◽

...

Keyword(s):

Crystal Structure ◽

Electron Diffraction ◽

Dft Calculations ◽

Density Functional ◽

Weak Interactions ◽

Diffraction Tomography ◽

X Ray Diffraction ◽

Orthorhombic Space Group ◽

X Ray ◽

Cell Parameters

AbstractThe crystal structure of karibibite, Fe33+(As3+O2)4(As23+O5)(OH), from the Urucum mine (Minas Gerais, Brazil), was solved and refined from electron diffraction tomography data [R1 = 18.8% for F > 4σ(F)] and further confirmed by synchrotron X-ray diffraction and density functional theory (DFT) calculations. The mineral is orthorhombic, space group Pnma and unit-cell parameters (synchrotron X-ray diffraction) are a = 7.2558(3), b = 27.992(1), c = 6.5243 (3) Å, V = 1325.10(8) Å3, Z = 4. The crystal structure of karibibbite consists of bands of Fe3+O6 octahedra running along a framed by two chains of AsO3 trigonal pyramids at each side, and along c by As2O5 dimers above and below. Each band is composed of ribbons of three edge-sharing Fe3+O6 octahedra, apex-connected with other ribbons in order to form a kinked band running along a. The atoms As(2) and As(3), each showing trigonal pyramidal coordination by O, share the O(4) atom to form a dimer. In turn, dimers are connected by the O(3) atoms, defining a zig-zag chain of overall (As3+O2)n-n stoichiometry. Each ribbon of (Fe3+O6) octahedra is flanked on both edges by the (As3+O2)n-n chains. The simultaneous presence of arsenite chains and dimers is previously unknown in compounds with As3+. The lone-electron pairs (4s2) of the As(2) and As(3) atoms project into the interlayer located at y = 0 and y = ½, yielding probable weak interactions with the O atoms of the facing (AsO2) chain.The DFT calculations show that the Fe atoms have maximum spin polarization, consistent with the Fe3+ state.

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XRD Analysis of Ferrite Ceramics with Different Heat Treatment

Materials Science Forum ◽

10.4028/www.scientific.net/msf.970.314 ◽

2019 ◽

Vol 970 ◽

pp. 314-319

Author(s):

Anatoly P. Surzhikov ◽

Sergei A. Ghyngazov ◽

Vitaly A. Vlasov ◽

Oldrich Stary ◽

Alexey N. Sokolovskiy

Keyword(s):

Heat Treatment ◽

Rietveld Method ◽

Structural Characteristics ◽

Xrd Analysis ◽

X Ray Diffraction ◽

Unit Cell Parameters ◽

X Ray ◽

Cell Parameters ◽

Qualitative And Quantitative ◽

Diffraction Patterns

A comparative analysis of the structural characteristics of LiZnTi ferrites sintered at the temperature of 1280 and 1360 K was performed. The qualitative and quantitative X-ray diffraction (XRD) analysis of the samples, main phase structural analysis, and unit cell parameters were carried out using the non-standard method (Rietveld method). Diffraction patterns were recorded on an ARL X'TRA diffractometer in the CuKα1+α2 and CuKβ scanning modes.

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X-ray powder diffraction data of LaNi0.5Ti0.45Co0.05O3, LaNi0.45Co0.05Ti0.5O3, and LaNi0.5Ti0.5O3 perovskites

Powder Diffraction ◽

10.1017/s0885715620000767 ◽

2021 ◽

pp. 1-6

Author(s):

Mariana M. V. M. Souza ◽

Alex Maza ◽

Pablo V. Tuza

Keyword(s):

Crystal Structure ◽

Rietveld Method ◽

Pechini Method ◽

Powder Diffraction Data ◽

X Ray Diffraction ◽

Unit Cell Parameters ◽

X Ray ◽

Cell Parameters ◽

Modified Pechini Method ◽

Scanning Electron

In the present work, LaNi0.5Ti0.45Co0.05O3, LaNi0.45Co0.05Ti0.5O3, and LaNi0.5Ti0.5O3 perovskites were synthesized by the modified Pechini method. These materials were characterized using X-ray fluorescence, scanning electron microscopy, and powder X-ray diffraction coupled to the Rietveld method. The crystal structure of these materials is orthorhombic, with space group Pbnm (No 62). The unit-cell parameters are a = 5.535(5) Å, b = 5.527(3) Å, c = 7.819(7) Å, V = 239.2(3) Å3, for the LaNi0.5Ti0.45Co0.05O3, a = 5.538(6) Å, b = 5.528(4) Å, c = 7.825(10) Å, V = 239.5(4) Å3, for the LaNi0.45Co0.05Ti0.5O3, and a = 5.540(2) Å, b = 5.5334(15) Å, c = 7.834(3) Å, V = 240.2(1) Å3, for the LaNi0.5Ti0.5O3.

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X-ray diffraction patterns for BaR2PdO5 (R=Nd, Sm, Eu, and Gd)

Powder Diffraction ◽

10.1017/s0885715600008800 ◽

1996 ◽

Vol 11 (1) ◽

pp. 9-12

Author(s):

W. Wong-Ng

Keyword(s):

Materials Characterization ◽

X Ray Diffraction ◽

Space Group ◽

X Ray ◽

Cell Parameters ◽

Diffraction Patterns ◽

The Eu

Calculated patterns for the BaR2PdO5 series, in which X is Pd and R=Nd, Sm, Eu, or Gd, have been prepared for materials characterization until experimental patterns can be determined. These compounds are isostructural to the superconductor related “brown phases” BaLa2CuO5 and BaNd2CuO5, which are tetragonal with space group P4/mbm, Z=4. The cell parameters of the Eu and Gd compounds were derived from the La and Nd analogs. The calculated patterns of these four compounds compared well to an experimental pattern of BaNd2CuO5.

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Structure Refinements of the Layered Intergrowth Phases SbIIISbV x A 1−x TiO6 (x≃0, A = Ta, Nb) Using Synchrotron X-ray Powder Diffraction Data

Acta Crystallographica Section B Structural Science ◽

10.1107/s0108768197007787 ◽

1997 ◽

Vol 53 (6) ◽

pp. 861-869 ◽

Cited By ~ 2

Author(s):

C. D. Ling ◽

J. G. Thompson ◽

S. Schmid ◽

D. J. Cookson ◽

R. L. Withers

Keyword(s):

Single Crystal ◽

Powder Diffraction ◽

Diffraction Data ◽

Homologous Series ◽

Rietveld Method ◽

Powder Diffraction Data ◽

X Ray Diffraction ◽

Synchrotron Source ◽

X Ray ◽

The Family

The structures of the layered intergrowth phases SbIIISb^{\rm V}_xAl-xTiO6 (x \simeq 0, A = Ta, Nb) have been refined by the Rietveld method, using X-ray diffraction data obtained using a synchrotron source. The starting models for these structures were derived from those of Sb^{\rm III}_3Sb^{\rm V}_xA 3−xTiO14 (x = 1.26, A = Ta and x = 0.89, A = Nb), previously solved by single-crystal X-ray diffraction. There were no significant differences between the derived models and the final structures, validating the approach used to obtain the models and confirming that the n = 1 and n = 3 members of the family, Sb^{\rm III}_nSb^{\rm V}_xA n−xTiO4n+2 are part of a structurally homologous series.

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Synthesis and properties of double gadolinium tellurites

Bulletin of the Karaganda University Chemistry series ◽

10.31489/2021ch3/67-73 ◽

2021 ◽

Vol 103 (3) ◽

pp. 67-73

Author(s):

A.A. Toibek ◽

◽

K.T. Rustembekov ◽

D.A. Kaikenov ◽

M. Stoev ◽

...

Keyword(s):

Phase Analysis ◽

Solid Phase ◽

Heat Capacities ◽

Ceramic Technology ◽

Phase Method ◽

X Ray Diffraction ◽

X Ray ◽

Cell Parameters ◽

Temperature Range ◽

Diffraction Patterns

For the first time, double gadolinium tellurites of the composition GdMIITeO4.5 (MII — Sr, Ba) were synthesized by the solid-phase method. The solid-phase synthesis of samples was carried out from decrepitated gadolinium (III) and tellurium (IV) oxides, strontium, and barium carbonates according to the standard ceramic technology. The synthesis was carried out in the temperature range of 800-1100 °C. The samples obtained were confirmed by X-ray phase analysis. X-ray phase analysis was carried out on an Empyrean instrument in the XRDML Pananalitical format. The intensity of the diffraction maxima was estimated on a 100-point scale. X-ray diffraction patterns indexing of the powder of gadolinium tellurites — alkaline earth metals studied were carried out by the homology method. The reliability and correctness of the results of indexing the X-ray diffraction patterns are confirmed by the good agreement between the experimental and calculated values of the interplanar distances (d) and the agreement between the values of the X-ray and pycnometric densities. It was found that compounds GdSrTeO4.5 and GdBaTeO4.5 crystallize in the monoclinic system and have the unit cell parameters, namely GdSrTeO4.5 — a = 12.7610, b = 10.4289, c = 8.6235 Å, V° = 1141.83 Å3, β = 95.77°, Z = 5, ρrent. = 3.22, ρpikn. = (3.10±0.09) g/cm3; GdBaTeO4.5 — a = 15.7272, b = 15.8351, c = 7.1393 Å, V° = 1769.72 Å3, β = 95.53°, Z = 8, ρrent = 3.71, ρpick = (3.61±0.10) g/cm3. Using the Landiya method, the standard heat capacities of the compounds were estimated from the calculated values of the standard entropies, and the temperature dependences of the heat capacities of the gadolinium tellurites synthesized were determined in the temperature range of 298–850 K.

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Bi3+ and Eu3+ Activated Luminescent Behaviors in Non-Stoichiometric LaO0.65F1.7 Structure

Materials ◽

10.3390/ma13102326 ◽

2020 ◽

Vol 13 (10) ◽

pp. 2326

Author(s):

Sungjun Yang ◽

Sangmoon Park

Keyword(s):

Optical Materials ◽

Emission Spectra ◽

Lattice Energy ◽

Host Lattice ◽

X Ray Diffraction ◽

Unit Cell Parameters ◽

X Ray ◽

Cell Parameters ◽

Diffraction Patterns ◽

Cation Sites

Optical materials composed of La1-p-qBipEuqO0.65F1.7 (p = 0.001–0.05, q = 0–0.1) were prepared via a solid-state reaction using La(Bi,Eu)2O3 and NH4F precursors at 1050 °C for two hours. X-ray diffraction patterns of the phosphors were obtained permitting the calculation of unit-cell parameters. The two La3+ cation sites were clearly distinguished by exploiting the photoluminescence excitation and emission spectra through Bi3+ and Eu3+ transitions in the non-stoichiometric host lattice. Energy transfer from Bi3+ to Eu3+ upon excitation with 286 nm radiation and its mechanism in the Bi3+- and Eu3+-doped host structures is discussed. The desired Commission Internationale de l’Eclairage values, including emissions in blue-green, white, and red wavelength regions, were obtained from the Bi3+- and Eu3+-doped LaO0.65F1.7 phosphors.

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Synthesis, Crystal Structure, Thermal Analysis, and DFT Calculations of Molecular Copper(II) Chloride Complexes with Bitopic Ligand 1,1,2,2-tetrakis(pyrazol-1-yl)ethane

Crystals ◽

10.3390/cryst9040222 ◽

2019 ◽

Vol 9 (4) ◽

pp. 222

Author(s):

Lider ◽

Sukhikh ◽

Smolentsev ◽

Semitut ◽

Filatov ◽

...

Keyword(s):

Dft Calculations ◽

Coordination Compounds ◽

Density Functional ◽

Water Molecules ◽

X Ray Diffraction ◽

Chloride Complexes ◽

Functional Theory ◽

X Ray ◽

Lattice Water ◽

Ir Bands

Two binuclear coordination compounds of Cu(II) chloride with the bitopic ligand 1,1,2,2-tetrakis(pyrazol-1-yl)ethane (Pz4) of the composition [Cu2(µ2Pz4)(DMSO)2Cl4]·4H2O and [Cu2(µ2Pz4)(DMSO)2Cl4]∙2DMSO were prepared and characterized by elemental analysis, IR spectroscopy, thermogravimetric analysis, single-crystal X-ray diffraction, and powder diffraction analysis. It was shown that in contrast to silver(I) and copper(II) nitrates, copper(II) chloride forms discrete complexes instead of coordination polymers. The supramolecular structure of the complex [Cu2(µ2Pz4)(DMSO)2Cl4]·4H2O with lattice water molecules is formed by OH···Cl and OH···O hydrogen bonds. Density functional theory (DFT) calculations of vibrational frequencies of the ligand and its copper(II) complex allowed for assigning IR bands to specific vibrations.

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High-Pressure Structural Behavior and Equation of State of Kagome Staircase Compound, Ni3V2O8

Crystals ◽

10.3390/cryst10100910 ◽

2020 ◽

Vol 10 (10) ◽

pp. 910

Author(s):

Daniel Diaz-Anichtchenko ◽

Robin Turnbull ◽

Enrico Bandiello ◽

Simone Anzellini ◽

Daniel Errandonea

Keyword(s):

High Pressure ◽

Equation Of State ◽

Density Functional ◽

Room Temperature ◽

Ambient Pressure ◽

Density Functional Theory Calculations ◽

X Ray Diffraction ◽

X Ray ◽

Cell Parameters ◽

A Chain

We report on high-pressure synchrotron X-ray diffraction measurements on Ni3V2O8 at room-temperature up to 23 GPa. According to this study, the ambient-pressure orthorhombic structure remains stable up to the highest pressure reached in the experiments. We have also obtained the pressure dependence of the unit-cell parameters, which reveals an anisotropic compression behavior. In addition, a room-temperature pressure–volume third-order Birch–Murnaghan equation of state has been obtained with parameters: V0 = 555.7(2) Å3, K0 = 139(3) GPa, and K0′ = 4.4(3). According to this result, Ni3V2O8 is the least compressible kagome-type vanadate. The changes of the crystal structure under compression have been related to the presence of a chain of edge-sharing NiO6 octahedral units forming kagome staircases interconnected by VO4 rigid tetrahedral units. The reported results are discussed in comparison with high-pressure X-ray diffraction results from isostructural Zn3V2O8 and density-functional theory calculations on several isostructural vanadates.

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Configurations and conformations of glycosyl sulfoxides

Canadian Journal of Chemistry ◽

10.1139/v10-091 ◽

2010 ◽

Vol 88 (11) ◽

pp. 1154-1174 ◽

Cited By ~ 6

Author(s):

Hong Liang ◽

Micheline MacKay ◽

T. Bruce Grindley ◽

Katherine N. Robertson ◽

T. Stanley Cameron

Keyword(s):

Solid State ◽

Dft Calculations ◽

Gas Phase ◽

Density Functional ◽

Lone Pair ◽

Azido Group ◽

X Ray Diffraction ◽

X Ray ◽

Comparison Of The Results ◽

P Type

X-ray crystallographic studies of two axial glycosyl sulfoxides having RS configurations (derivatives of phenyl 2-azido-2-deoxy-1-thio-α-d-galactopyranoside S-oxide) show that they adopt anti conformations in the solid state, in contrast to previous observations and assumptions. Density functional theory (DFT) calculations at the B3lYP6–311G+(d,p)/6–31G(d) level confirm that anti conformations of both phenyl and methyl RS glycosyl sulfoxides of 2-azido-2-deoxy-α-d-pyranosides are more stable than exo-anomeric conformations in the gas phase. 1D NOE measurements indicate that the more polar exo-anomeric conformers are only populated to a slight extent in solution. The anti conformations are distorted so that the glycosyl substituents are closer to being eclipsed with H1. This distortion allows S n → σ* overlap if the sulfur lone pair is a p-type lone pair. Evidence for this overlap comes from short C1–S bond distances, as short as the comparable bond distances in the X-ray crystal structure and in the results from DFT calculations for the SS glycoside, which does adopt the expected exo-anomeric conformation, both in the solid state and in solution, and has normal n → σ* overlap. For 2-deoxy derivatives not bearing a 2-azido group, gas-phase DFT calculations at the same level indicate that the anti- and exo-anomeric conformers have comparable stabilities. Comparison of the results of the two series shows that electronegative substituents in equatorial orientations at C2 destabilize conformations with parallel S–O arrangements, the conformation favored by having an endocyclic C–O dipole antiparallel to the S–O dipole, by about 2.5 kcal mol–1 (1 cal = 4.184 J). An equatorial glycosyl sulfoxide, (SS) phenyl 3,4,6-tri-O-acetyl-2-deoxy-2-phthalimido-1-thio-β-d-glucopyranoside S-oxide, also adopts an anti conformation in the solid state as shown by X-ray diffraction. It also adopts this conformation in solution, in contrast to studies of other equatorial glycosyl sulfoxides.

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