scholarly journals Pressure-induced Pb–Pb bonding and phase transition in Pb2SnO4

2020 ◽  
Vol 76 (6) ◽  
pp. 979-991
Author(s):  
Dominik Spahr ◽  
Michał Stękiel ◽  
Dominik Zimmer ◽  
Lkhamsuren Bayarjargal ◽  
Katja Bunk ◽  
...  
Keyword(s):  
Phase Transition ◽  
Density Functional Theory ◽  
High Pressure ◽  
Powder Diffraction ◽  
Density Functional ◽  
Structural Phase ◽  
Irreducible Representations ◽  
Ambient Conditions ◽  
Functional Theory ◽  
Electron Pairs

High-pressure single-crystal to 20 GPa and powder diffraction measurements to 50 GPa, show that the structure of Pb2SnO4 strongly distorts on compression with an elongation of one axis. A structural phase transition occurs between 10 GPa and 12 GPa, with a change of space group from Pbam to Pnam. The resistivity decreases by more than six orders of magnitude when pressure is increased from ambient conditions to 50 GPa. This insulator-to-semiconductor transition is accompanied by a reversible appearance change from transparent to opaque. Density functional theory-based calculations show that at ambient conditions the channels in the structure host the stereochemically-active Pb 6s 2 lone electron pairs. On compression the lone electron pairs form bonds between Pb2+ ions. Also provided is an assignment of irreducible representations to the experimentally observed Raman bands.

Janus monolayer of WSeTe, a new structural phase transition material driven by electrostatic gating

Nanoscale ◽  
2018 ◽  
Vol 10 (46) ◽  
pp. 21629-21633 ◽  
Author(s):  
Yajing Sun ◽  
Zhigang Shuai ◽  
Dong Wang
Keyword(s):  
Phase Transition ◽  
Density Functional Theory ◽  
Structural Phase Transition ◽  
Density Functional ◽  
Structural Phase ◽  
Density Functional Theory Calculations ◽  
Functional Theory ◽  
Electrostatic Gating ◽  
Phase Transition Kinetics

By density functional theory calculations, we show that the Janus monolayer of WSeTe has faster semiconductor–semimetal phase transition kinetics than MoTe2.

scholarly journals DFT Calculations of the Structural, Mechanical, and Electronic Properties of TiV Alloy Under High Pressure

Symmetry ◽  
2019 ◽  
Vol 11 (8) ◽  
pp. 972 ◽  
Author(s):  
Fang Yu ◽  
Yu Liu
Keyword(s):  
Phase Transition ◽  
High Pressure ◽  
Electronic Properties ◽  
Structural Phase Transition ◽  
Density Functional ◽  
Structural Phase ◽  
Applied Pressure ◽  
Functional Theory ◽  
The Density Functional Theory ◽  
Dimensionless Ratio

A calculation program based on the density functional theory (DFT) is applied to study the structural, mechanical, and electronic properties of TiV alloys with symmetric structure under high pressure. We calculate the dimensionless ratio, elastic constants, shear modulus, Young’s modulus, bulk modulus, ductile-brittle transition, material anisotropy, and Poisson’s ratio as functions of applied pressure. Results suggest that the critical pressure of structural phase transition is 42.05 GPa for the TiV alloy, and structural phase transition occurs when the applied pressure exceeds 42.05 GPa. High pressure can improve resistance to volume change, as well as the ductility and atomic bonding, but the strongest resistances to elastic and shear deformation occur at P = 5   GPa for TiV alloy. Furthermore, the results of the density of states (DOS) indicate that the TiV alloy presents metallicity. High pressure disrupts the structural stability of the TiV alloy with symmetry, thereby inducing structural phase transition.

scholarly journals Stability and electronic structure of magnesium hydride and magnesium deuteride under high pressure

2021 ◽  
Vol 2145 (1) ◽  
pp. 012026
Author(s):  
Chayaphon Boonchot ◽  
Prutthipong Tsuppayakorn-Aek ◽  
Udomsilp Pinsook ◽  
Thiti Bovornratanaraks
Keyword(s):  
Phase Transition ◽  
Density Functional Theory ◽  
High Pressure ◽  
Electronic Structure ◽  
Density Functional ◽  
Formation Enthalpy ◽  
Band Structures ◽  
Functional Theory ◽  
Superconducting Metal ◽  
Quantum Espresso

Abstract Metal polyhydrides have attracted considerable attention because some of them become a metal under high pressure, and some undergo a phase transition into a superconductor. Some superconducting metal polyhydrides have recently been discovered with a high value of critical temperature (Tc) under pressure. In this research, we calculated the structures of MgH2, MgH3 and MgD3 under pressure between 0-300 GPa in order to determine the formation enthalpy and electronic property of their structures under high pressure by using density functional theory (DFT) based on the Quantum Espresso code. We found that the band structures reveal the metallic character of the compounds under high pressure. The energy band structures of MgHx and MgDx are exactly the same. However, their phonon dispersions are different due to the so-called isotope effect. We determined the composition stability by using the convex hull of Mg, H and the compounds. We found that MgH3 becomes thermodynamically more stable than MgH2 at around 150 GPa. The results of phonons confirm that they are dynamically stable. This finding is served as a basis for future superconducting calculations.

Revised prediction of B1 to B2 phase transition pressures in YbN, YbP and YbAs

2005 ◽  
Vol 220 (8) ◽  
Author(s):  
Björn Winkler ◽  
Victor Milman
Keyword(s):  
Phase Transition ◽  
Density Functional Theory ◽  
Density Functional ◽  
Structural Phase ◽  
Quantum Mechanical ◽  
Quantum Mechanical Calculations ◽  
Generalized Gradient ◽  
Functional Theory ◽  
Model Calculations ◽  
B2 Phase

AbstractQuantum mechanical calculations based on density functional theory and a generalized gradient approx imation have been used to study the pressure-induced B1 to B2 structural phase transition in YbN, YbP and YbAs. The phase transitions are predicted to occur at 137 GPa in YbN, at 25 GPa in YbP, and at 20 GPa in YbAs. These values are significantly lower than those predicted by empirical poten tial model calculations. Bulk moduli are predicted to be 136, 70 and 63 GPa for YbN, YbP and YbAs, respectively.

scholarly journals High-Pressure Study of Two Polymorphs of 2,4,6-Trinitrotoluene Using Neutron Powder Diffraction and Density Functional Theory Methods

2019 ◽  
Vol 123 (43) ◽  
pp. 26095-26105 ◽  
Author(s):  
Sumit Konar ◽  
Adam A. L. Michalchuk ◽  
Nilgun Sen ◽  
Craig L. Bull ◽  
Carole A. Morrison ◽  
...  
Keyword(s):  
Density Functional Theory ◽  
High Pressure ◽  
Powder Diffraction ◽  
Density Functional ◽  
Neutron Powder Diffraction ◽  
Functional Theory ◽  
High Pressure Study

Phase Transition and Elastic Properties of Zinc Sulfide Under High Pressure from First Principles Calculations

2011 ◽  
Vol 66 (10-11) ◽  
pp. 656-660
Author(s):  
Dai Wei ◽  
Song Jin-Fan ◽  
Wang Ping ◽  
Lu Cheng ◽  
Lu Zhi-Wen ◽  
...  
Keyword(s):  
Phase Transition ◽  
High Pressure ◽  
Zinc Sulfide ◽  
Elastic Properties ◽  
First Principles ◽  
Density Functional ◽  
Theoretical Calculations ◽  
Structural Phase ◽  
Functional Theory ◽  
The Density Functional Theory

A theoretical investigation on structural and elastic properties of zinc sulfide semiconductor under high pressure is performed by employing the first-principles method based on the density functional theory. The calculated results show that the transition pressure Pt for the structural phase transition from the B3 structure to the B1 structure is 17:04 GPa. The calculated values are generally speaking in good agreement with experiments and with similar theoretical calculations.

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