scholarly journals Theoretical and experimental studies of compression and shear deformation behavior of Osmium to 280 GPa

2021 ◽  
Author(s):  
Chia Min Lin ◽  
Kaleb C Burrage ◽  
Chris Perreault ◽  
Wei-Chih Chen ◽  
Cheng-Chien Chen ◽  
...  
Keyword(s):  
Shear Stress ◽  
Shear Strength ◽  
Dft Calculations ◽  
Density Functional ◽  
Theoretical Calculations ◽  
Experimental Studies ◽  
Axial Ratio ◽  
Shear Direction ◽  
X Ray Diffraction ◽  
X Ray

Abstract The compression behavior of osmium metal was investigated up to 280 GPa (volume compression V/Vo =0.725) under nonhydrostatic conditions at ambient temperature using angle dispersive axial x-ray diffraction (A-XRD) with a diamond anvil cell (DAC). In addition, shear strength of osmium was measured to 170 GPa using radial x-ray diffraction (R-XRD) technique in DAC. Both diffraction techniques in DAC employed platinum as an internal pressure standard. Density functional theory (DFT) calculations were also performed, and the computed lattice parameters and volumes under compression are in good agreement with the experiments. DFT predicts a monotonous increase in axial ratio (c/a) with pressure and the structural anomalies of less than 1 % in (c/a) ratio below 150 GPa were not reproduced in theoretical calculations and hydrostatic measurements. The measured value of shear strength of osmium (τ) approaches a limiting value of 6 GPa above a pressure of 50 GPa in contrast to theoretical predictions of 24 GPa and is likely due to imperfections in polycrystalline samples. DFT calculations also enable the studies of shear and tensile deformations. The theoretical ideal shear stress is found along the (001)[1-10] shear direction with the maximal shear stress ~24 GPa at critical strain ~0.13.

scholarly journals 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 ◽  
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.

Structure and conformational analysis of a bidentate pro-ligand, C21H34N2S2, from powder synchrotron diffraction data and solid-state DFTB calculations

2009 ◽  
Vol 65 (5) ◽  
pp. 639-646 ◽  
Author(s):  
Edward E. Ávila ◽  
Asiloé J. Mora ◽  
Gerzon E. Delgado ◽  
Ricardo R. Contreras ◽  
Luis Rincón ◽  
...  
Keyword(s):  
Solid State ◽  
Diffraction Data ◽  
Density Functional ◽  
Simulated Annealing Algorithm ◽  
Theoretical Calculations ◽  
Tight Binding ◽  
Van Der Waals Interactions ◽  
Am1 Calculations ◽  
X Ray Diffraction ◽  
X Ray

The molecular and crystalline structure of ethyl 1′,2′,3′,4′,4a′,5′,6′,7′-octahydrodispiro[cyclohexane-1,2′-quinazoline-4′,1′′-cyclohexane]-8′-carbodithioate (I) was solved and refined from powder synchrotron X-ray diffraction data. The initial model for the structural solution in direct space using the simulated annealing algorithm implemented in DASH [David et al. (2006). J. Appl. Cryst. 39, 910–915] was obtained performing a conformational study on the fused six-membered rings of the octahydroquinazoline system and the two spiran cyclohexane rings of (I). The best model was chosen using experimental evidence from 1H and 13C NMR [Contreras et al. (2001). J. Heterocycl. Chem. 38, 1223–1225] in combination with semi-empirical AM1 calculations. In the refined structure the two spiran rings have the chair conformation, while both of the fused rings in the octahydroquinazoline system have half-chair conformations compared with in-vacuum density-functional theory (DFT) B3LYP/6-311G*, DFTB (density-functional tight-binding) theoretical calculations in the solid state and other related structures from X-ray diffraction data. Compound (I) presents weak intramolecular hydrogen bonds of the type N—H...S and C—H...S, which produce delocalization of the electron density in the generated rings described by graph symbols S(6) and S(5). Packing of the molecules is dominated by van der Waals interactions.

Configurations and conformations of glycosyl sulfoxides

2010 ◽  
Vol 88 (11) ◽  
pp. 1154-1174 ◽  
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.

Combined analysis of chemical bonding in a CuIIdimer using QTAIM, Voronoi tessellation and Hirshfeld surface approaches

2015 ◽  
Vol 71 (5) ◽  
pp. 543-554 ◽  
Author(s):  
Anna V. Vologzhanina ◽  
Svitlana V. Kats ◽  
Larisa V. Penkova ◽  
Vadim A. Pavlenko ◽  
Nikolay N. Efimov ◽  
...  
Keyword(s):  
Dft Calculations ◽  
Density Functional ◽  
Voronoi Tessellation ◽  
Quantitative Description ◽  
Hirshfeld Surface ◽  
Epr Spectra ◽  
Antiferromagnetic Coupling ◽  
X Ray Diffraction ◽  
Spin Distribution ◽  
X Ray

Interaction of 1-(1H-pyrazol-5-yl)ethanone oxime (H2PzOx) with copper(II) chloride in the presence of pyridine afforded a binuclear discrete [Cu2(HPzOx)2Cl2py2] complex, which was characterized by Fourier transform–IR and electron paramagnetic resonance (EPR) spectra, magnetochemistry and high-resolution X-ray diffraction experiments. Multipole refinement of X-ray diffraction data and density-functional theory (DFT) calculations of an isolated molecule allowed charge and spin distributions to be obtained for this compound. Magnetochemistry data, EPR spectra and DFT calculations of an isolated molecule show antiferromagnetic coupling between copper(II) ions. The spin distribution suggests an exchange pathwayviathe bridging pyrazole ring in the equatorial plane of the CuN4Cl coordination polyhedron, thus providing support for the classical superexchange mechanism; the calculated value of the magnetic coupling constant −2Jis equal to 220 cm−1, which compares well with the experimental value of 203 ± 2 cm−1. Chemical connectivity was derived by Bader's `quantum theory of atoms in molecules' and compared with Voronoi tessellation and Hirshfeld surface representations of crystal space. All methodologies gave a similar qualitative and semi-quantitative description of intra- and intermolecular connectivity.

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

2017 ◽  
Vol 81 (5) ◽  
pp. 1191-1202 ◽  
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.

scholarly journals Structural and electronic properties of the spinel Li4Ti5O12

2019 ◽  
Vol 20 (46) ◽  
pp. 7-12 ◽  
Author(s):  
Sarantuya Lkhagvajav ◽  
Namsrai Tsogbadrakh ◽  
Enkhjargal Enkhbayar ◽  
Sevjidsuren Galsan ◽  
Pagvajav Altantsog
Keyword(s):  
Electronic Properties ◽  
First Principles ◽  
Density Functional ◽  
Experimental Studies ◽  
First Principles Calculations ◽  
X Ray Diffraction ◽  
X Ray ◽  
Structural And Electronic Properties ◽  
Hubbard U ◽  
Uv Visible

In this study, the structure and electronic properties of the spinel compound Li4Ti5O12 (LTO) are investigated both theoretical and experimental methods. The experimental studies of structural and electronic properties were performed by X-ray diffraction and UV-visible spectroscopy. The first principles calculations allowed to establish the relationship between the structure and electronic properties. The spinel type structure of LTO is refined by the Rietveld analysis using the X-ray diffraction (XRD). The band gap of LTO was determined to be 3.55 eV using the UV-visible absorption spectra. The Density functional theory (DFT) augmented without and with the Hubbard U correction (GGA and GGA +U+J0) is used to elucidate the electronic structure of LTO. We have performed systematic studies of the first principles calculations based on the GGA and GGA+U for the crystal structure and electronic properties of spinel LTO. We propose that a Hubbard U correction improves the DFT results.

X-ray and DFT Investigation of (E)-4-bromo-5-methoxy-2-((o-tolylimino)methyl)phenol Compound

2018 ◽  
pp. 454-461
Keyword(s):  
Density Functional ◽  
Theoretical Calculations ◽  
Population Analysis ◽  
Diffraction Method ◽  
Dft Method ◽  
Basis Set ◽  
X Ray Diffraction ◽  
Mulliken Population ◽  
Charge Delocalization ◽  
X Ray

(E)-4-bromo-5-methoxy-2-((o-tolylimino)methyl)phenol was investigated by experimental and theoretical methodologies. The solid state molecular structure was determined by X-ray diffraction method. All theoretical calculations were performed by density functional theory (DFT) method by using B3LYP/6-31G(d,p) basis set. The titled compound showed the preference of enol form, as supported by X-ray diffraction method. The geometric and molecular properties were compaired for both enol-imine and keto-amine forms for title compound. Stability of the molecule arises from hyperconjugative interactions, charge delocalization and intramolecular hydrogen bond has been analyzed using natural bond orbital (NBO) analysis. Mulliken population method and natural population analysis (NPA) have been studied. Also, condensed Fukui function and relative nucleophilicity indices calculated from charges obtained with orbital charge calculation methods (NPA). Molecular electrostatic potential (MEP) and non linear optical (NLO) properties are also examined.

scholarly journals Pressure-dependent X-ray diffraction of the multiferroics RMn2O5

2019 ◽  
Vol 75 (4) ◽  
pp. 687-696 ◽  
Author(s):  
Wei Peng ◽  
Victor Balédent ◽  
Marie-Bernadette Lepetit ◽  
Antoine Vaunat ◽  
Elisa Rebolini ◽  
...  
Keyword(s):  
Dft Calculations ◽  
Density Functional ◽  
Room Temperature ◽  
Exchange Interactions ◽  
X Ray Diffraction ◽  
Functional Theory ◽  
X Ray ◽  
X Ray Scattering ◽  
Pressure Evolution ◽  
Good Agreement

The room-temperature structural properties of the RMn2O5 multiferroics have been investigated under pressure, using powder X-ray scattering and density functional theory (DFT) calculations. It was possible to determine the lattice parameters and the main atomic positions as a function of pressure. Good agreement was observed between the X-ray and DFT results for most of the determined crystallographic data. From the DFT calculations, it was possible to infer the pressure evolution of the exchange interactions, and this analysis led to the conclusion that the onset of the q = (½, 0, ½) magnetic structure under pressure is related to the increase in the J 1 super-exchange terms (due to the reduction in the Mn—O distances) compared with the Mn—R exchange interactions. In addition, the 1D antiferromagnetic character of the compounds should be reinforced under pressure.

scholarly journals Synthesis of Pure NiTiSn by Mechanical Alloying: An Investigation of the Optimal Experimental Conditions Supported by First Principles Calculations

Metals ◽  
2018 ◽  
Vol 8 (10) ◽  
pp. 835 ◽  
Author(s):  
Monique Tillard ◽  
Alexandre Berche ◽  
Philippe Jund
Keyword(s):  
Mechanical Alloying ◽  
Density Functional ◽  
Annealing Temperature ◽  
Theoretical Calculations ◽  
First Principles Calculations ◽  
X Ray Diffraction ◽  
Experimental Conditions ◽  
Functional Theory ◽  
X Ray ◽  
Careful Investigation

Synthesis of NiTiSn by a mechanical alloying process followed by a high temperature thermal annealing was studied. Experiments were conducted varying parameters like the provided energy, the mechanical alloying reaction time, as well as the annealing temperature and duration. Based on the careful investigation of the phases present in the samples by systematic X-ray diffraction (after mechanical alloying and after annealing) and selected microscopy analyses, a reaction mechanism is proposed supported by theoretical calculations at the DFT (Density Functional Theory) level. An energy window to prepare directly NiTiSn has been evidenced. Highly pure NiTiSn has also been obtained by conversion from a multicomponent precursor obtained by low energy mechanical alloying.

Optical limiting properties, structure and simplified TD-DFT calculations of scandium tetra-15-crown-5 phthalocyaninates

2020 ◽  
Vol 24 (04) ◽  
pp. 589-601 ◽  
Author(s):  
Aviwe May ◽  
Poulomi Majumdar ◽  
Alexander G. Martynov ◽  
Lyudmila A. Lapkina ◽  
Sergey I. Troyanov ◽  
...  
Keyword(s):  
Dft Calculations ◽  
Density Functional ◽  
Theoretical Calculations ◽  
Optical Limiting ◽  
X Ray Diffraction ◽  
Compound I ◽  
Neutral Radical ◽  
Organic Chromophores ◽  
Sandwich Compound ◽  
Td Dft

The optical limiting properties of crown-ether-substituted scandium(III) phthalocyaninate complexes, bis-tetra-15-crown-5-phthalocyaninates Sc[(15C5)4Pc][Formula: see text] (I) and Sc[(15C5)4Pc][Formula: see text] (Ia), together with monophthalocyaninate [(15C5)4Pc]Sc(OAc) (II) were measured by using the Z-scan technique (532 nm laser and pulse rate of 10 ns). It was revealed that expansion of the [Formula: see text]-system on moving from the monomeric Sc complex II to sandwich compound I and changing the electronic state of the sandwich compound from the anionic Ia species to the neutral radical I improves the optical limiting properties. The Im[[Formula: see text]] values obtained lie in the 10[Formula: see text]–10[Formula: see text] esu range that is consistent with those reported previously for other organic chromophores. The crystal structure of sandwich Sc(III) complex I was elucidated by means of single-crystal X-ray diffraction analysis and was used to guide a series of theoretical calculations. It was demonstrated that the application of simplified time-dependent density functional theory (sTD-DFT) calculations can provide reasonably accurate predictions for compounds of this type when the geometries of the complexes are clearly defined.

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