scholarly journals Can We Predict the Isosymmetric Phase Transition? Application of DFT Calculations to Study the Pressure Induced Transformation of Chlorothiazide

2021 ◽  
Vol 22 (18) ◽  
pp. 10100
Author(s):  
Łukasz Szeleszczuk ◽  
Anna Helena Mazurek ◽  
Katarzyna Milcarz ◽  
Ewa Napiórkowska ◽  
Dariusz Maciej Pisklak
Keyword(s):  
Phase Transition ◽  
Dft Calculations ◽  
Structural Phase ◽  
Geometry Optimization ◽  
Group Symmetry ◽  
Ab Initio Molecular Dynamics ◽  
Diuretic Agent ◽  
Molecular Dynamics Calculations ◽  
Secondary Function ◽  
Periodic Dft Calculations

Isosymmetric structural phase transition (IPT, type 0), in which there are no changes in the occupation of Wyckoff positions, the number of atoms in the unit cell, and the space group symmetry, is relatively uncommon. Chlorothiazide, a diuretic agent with a secondary function as an antihypertensive, has been proven to undergo pressure-induced IPT of Form I to Form II at 4.2 GPa. For that reason, it has been chosen as a model compound in this study to determine if IPT can be predicted in silico using periodic DFT calculations. The transformation of Form II into Form I, occurring under decompression, was observed in geometry optimization calculations. However, the reverse transition was not detected, although the calculated differences in the DFT energies and thermodynamic parameters indicated that Form II should be more stable at increased pressure. Finally, the IPT was successfully simulated using ab initio molecular dynamics calculations.

X-ray diffraction and Raman study of DL-alanine at high pressure: revision of phase transitions

2012 ◽  
Vol 68 (4) ◽  
pp. 412-423 ◽  
Author(s):  
Nikolay A. Tumanov ◽  
Elena V. Boldyreva
Keyword(s):  
Phase Transition ◽  
Phase Transitions ◽  
Structural Phase ◽  
Group Symmetry ◽  
Second Phase ◽  
Structural Phase Transitions ◽  
X Ray Diffraction ◽  
X Ray ◽  
Cell Parameters ◽  
Raman Study

The effect of pressure on DL-alanine has been studied by X-ray powder diffraction (up to 8.3 GPa), single-crystal X-ray diffraction and Raman spectroscopy (up to ∼ 6 GPa). No structural phase transitions have been observed. At ∼ 1.5–2 GPa, cell parameters b and c become accidentally equal to each other, but the space-group symmetry does not change. There is no phase transition between 1.7 and 2.3 GPa, contrary to what has been reported earlier [Belo et al. (2010). Vibr. Spectrosc. 54, 107–111]. The presence of the second phase transition, which was claimed to appear within the pressure range from 6.0 to 7.3 GPa (Belo et al., 2010), is also argued. The changes in the Raman spectra have been shown to be continuous in all the pressure ranges studied.

A structural phase transition in NaTaOGeO4 and its relation to phase transitions in titanite

2007 ◽  
Vol 63 (4) ◽  
pp. 545-550 ◽  
Author(s):  
Thomas Malcherek
Keyword(s):  
Phase Transition ◽  
Phase Transitions ◽  
Transition Metal ◽  
Structural Phase Transition ◽  
Order Parameter ◽  
Diffuse Scattering ◽  
Structural Phase ◽  
Group Symmetry ◽  
Critical Temperatures ◽  
Symmetry Properties

A structural phase transition from space-group symmetry P21/c to C2/c is reported for NaTaOGeO4 (NTGO). The critical temperature has been located at T c = 116 K, based on the appearance of sharp diffraction maxima at positions h + k = 2n + 1 of reciprocal space on cooling below this temperature. Strongly anisotropic diffuse scattering in sheets normal to [001] is observable for T > T c and persists up to ambient temperature. Similarities to phase transitions observed in other compounds of the titanite structure type are discussed. The symmetry properties of these phase transitions are reassessed on the basis of the structural data available. The primary order parameter is identified with the displacement of the transition metal cation M (M = Ta in NTGO) away from the centre of symmetry that it nominally occupies in the paraphase. The order parameter transforms as the Y_{2}^{-} representation. The anisotropic diffuse scattering is attributed to the one-dimensional correlation of local M displacements parallel to the direction of chains of trans-corner-sharing MO6 octahedra. The critical temperatures of the isomorphous phase transitions in various titanite-type compounds depend linearly on the squared transition-metal displacement measured in the ordered P21/c phase.

Structural Phase Transition of Multilayer VSe2

2020 ◽  
Vol 12 (22) ◽  
pp. 25143-25149 ◽  
Author(s):  
Dian Li ◽  
Xiong Wang ◽  
Chi-ming Kan ◽  
Daliang He ◽  
Zejun Li ◽  
...  
Keyword(s):  
Phase Transition ◽  
Structural Phase Transition ◽  
Structural Phase

scholarly journals Raman spectroscopy study of the behavior of the soft mode in a structural phase transition in the Pr3Sb5O12 crystal

2015 ◽  
Vol 57 (11) ◽  
pp. 2286-2289 ◽  
Author(s):  
A. S. Oreshonkov ◽  
A. K. Khodzhibaev ◽  
A. S. Krylov ◽  
M. F. Umarov ◽  
A. N. Vtyurin
Keyword(s):  
Phase Transition ◽  
Raman Spectroscopy ◽  
Structural Phase Transition ◽  
Soft Mode ◽  
Structural Phase ◽  
Spectroscopy Study

Optical Switching of Coherent VO2 Precipitates Embedded in Sapphire

1995 ◽  
Vol 396 ◽  
Author(s):  
L. A. Gea ◽  
L. A. Boatner ◽  
J. D. Budai ◽  
R. A. Zuhr
Keyword(s):  
Phase Transition ◽  
Vanadium Dioxide ◽  
Thermal Processing ◽  
Optical Switching ◽  
Optical Transmission ◽  
Structural Phase ◽  
Switching Behavior ◽  
New Type ◽  
Single Crystal Sapphire ◽  
Smart Surface

AbstractIn this work, we report the formation of a new type of active or “smart” surface that is produced by ion implantation and thermal processing. By co-implanting vanadium and oxygen into a single-crystal sapphire substrate and annealing the system under appropriate conditions, it was possible to form buried precipitates of vanadium dioxide that were crystallographically oriented with respect to the host AI2O3 lattice. The implanted VO2 precipitate system undergoes a structural phase transition that is accompanied by large variations in the optical transmission which are comparable to those observed for thin films of VO2 deposited on sapphire. Co-implantation with oxygen was found to be necessary to ensure good optical switching behavior.

scholarly journals The origin of the lattice thermal conductivity enhancement at the ferroelectric phase transition in GeTe

2021 ◽  
Vol 7 (1) ◽  
Author(s):  
Đorđe Dangić ◽  
Olle Hellman ◽  
Stephen Fahy ◽  
Ivana Savić
Keyword(s):  
Phase Transition ◽  
Thermal Conductivity ◽  
Phase Transitions ◽  
Thermoelectric Materials ◽  
Ferroelectric Phase Transition ◽  
Lattice Thermal Conductivity ◽  
Ferroelectric Phase ◽  
Structural Phase ◽  
High Symmetry ◽  
Structural Phase Transitions

AbstractThe proximity to structural phase transitions in IV-VI thermoelectric materials is one of the main reasons for their large phonon anharmonicity and intrinsically low lattice thermal conductivity κ. However, the κ of GeTe increases at the ferroelectric phase transition near 700 K. Using first-principles calculations with the temperature dependent effective potential method, we show that this rise in κ is the consequence of negative thermal expansion in the rhombohedral phase and increase in the phonon lifetimes in the high-symmetry phase. Strong anharmonicity near the phase transition induces non-Lorentzian shapes of the phonon power spectra. To account for these effects, we implement a method of calculating κ based on the Green-Kubo approach and find that the Boltzmann transport equation underestimates κ near the phase transition. Our findings elucidate the influence of structural phase transitions on κ and provide guidance for design of better thermoelectric materials.

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