Disclosing the behavior under hydrostatic pressure of rhombohedral MgIn2Se4 by means of first-principles calculations

2020 ◽  
Vol 22 (38) ◽  
pp. 21909-21918 ◽  
Author(s):  
Khaled Boukri ◽  
Tarik Ouahrani ◽  
Michael Badawi ◽  
Kamel Demmouche ◽  
Ruth Franco ◽  
...  
Keyword(s):  
Phase Transition ◽  
Hydrostatic Pressure ◽  
First Principles ◽  
Van Der Waals ◽  
Van Der Waals Interactions ◽  
First Principles Calculations ◽  
Inverse Spinel

The rhombohedral layered MgIn2Se4 undergoes a pressure-induced phase transition to an inverse spinel one, loses its van der Waals interactions, and becomes more covalent.

scholarly journals First-principles calculations and experimental studies of XYZ2 thermoelectric compounds: detailed analysis of van der Waals interactions

2018 ◽  
Vol 6 (40) ◽  
pp. 19502-19519 ◽  
Author(s):  
Jan-Hendrik Pöhls ◽  
Zhe Luo ◽  
Umut Aydemir ◽  
Jon-Paul Sun ◽  
Shiqiang Hao ◽  
...  
Keyword(s):  
Detailed Analysis ◽  
First Principles ◽  
Van Der Waals ◽  
Experimental Studies ◽  
Van Der Waals Interactions ◽  
First Principles Calculations ◽  
Prediction Of Properties

van der Waals interactions enhanced the prediction of properties in layered thermoelectrics.

scholarly journals Coexistence of plastic and partially diffusive phases in a helium-methane compound

2020 ◽  
Vol 7 (10) ◽  
pp. 1540-1547
Author(s):  
Hao Gao ◽  
Cong Liu ◽  
Andreas Hermann ◽  
Richard J Needs ◽  
Chris J Pickard ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Phase Diagram ◽  
First Principles ◽  
Van Der Waals ◽  
Van Der Waals Interactions ◽  
First Principles Calculations ◽  
Helium Atoms ◽  
Wide Range ◽  
Pure Methane ◽  
The Universe

Abstract Helium and methane are major components of giant icy planets and are abundant in the universe. However, helium is the most inert element in the periodic table and methane is one of the most hydrophobic molecules, thus whether they can react with each other is of fundamental importance. Here, our crystal structure searches and first-principles calculations predict that a He3CH4 compound is stable over a wide range of pressures from 55 to 155 GPa and a HeCH4 compound becomes stable around 105 GPa. As nice examples of pure van der Waals crystals, the insertion of helium atoms changes the original packing of pure methane molecules and also largely hinders the polymerization of methane at higher pressures. After analyzing the diffusive properties during the melting of He3CH4 at high pressure and high temperature, in addition to a plastic methane phase, we have discovered an unusual phase which exhibits coexistence of diffusive helium and plastic methane. In addition, the range of the diffusive behavior within the helium-methane phase diagram is found to be much narrower compared to that of previously predicted helium-water compounds. This may be due to the weaker van der Waals interactions between methane molecules compared to those in helium-water compounds, and that the helium-methane compound melts more easily.

The Key Role of van der Waals Interactions in MPc/Au(111) (M = Co, Fe, H2) Systems Based on First-Principles Calculations

2014 ◽  
Vol 118 (48) ◽  
pp. 27843-27849 ◽  
Author(s):  
Shaoyuan Li ◽  
Jialei Hao ◽  
Feifei Li ◽  
Ziping Niu ◽  
Zhenpeng Hu ◽  
...  
Keyword(s):  
First Principles ◽  
Van Der Waals ◽  
Van Der Waals Interactions ◽  
First Principles Calculations

Thermodynamic Stability of Hexagonal and Rhombohedral Bn at Cvd Conditions from Van der Waals Corrected First Principles Calculations

2019 ◽  
Author(s):  
Henrik Pedersen ◽  
Björn Alling ◽  
Hans Högberg ◽  
Annop Ektarawong
Keyword(s):  
Thin Films ◽  
Thermodynamic Stability ◽  
First Principles ◽  
Thermal Equilibrium ◽  
Density Functional ◽  
Van Der Waals ◽  
Chemical Vapor ◽  
First Principles Calculations ◽  
Functional Theory ◽  
The Stability

Thin films of boron nitride (BN), particularly the sp<sup>2</sup>-hybridized polytypes hexagonal BN (h-BN) and rhombohedral BN (r-BN) are interesting for several electronic applications given band gaps in the UV. They are typically deposited close to thermal equilibrium by chemical vapor deposition (CVD) at temperatures and pressures in the regions 1400-1800 K and 1000-10000 Pa, respectively. In this letter, we use van der Waals corrected density functional theory and thermodynamic stability calculations to determine the stability of r-BN and compare it to that of h-BN as well as to cubic BN and wurtzitic BN. We find that r-BN is the stable sp<sup>2</sup>-hybridized phase at CVD conditions, while h-BN is metastable. Thus, our calculations suggest that thin films of h-BN must be deposited far from thermal equilibrium.

Orbital change manipulation metal–insulator transition temperature in W-doped VO2

2015 ◽  
Vol 17 (17) ◽  
pp. 11638-11646 ◽  
Author(s):  
Xinfeng He ◽  
Yijie Zeng ◽  
Xiaofeng Xu ◽  
Congcong Gu ◽  
Fei Chen ◽  
...  
Keyword(s):  
Phase Transition ◽  
Infrared Spectroscopy ◽  
Transition Temperature ◽  
Phase Transition Temperature ◽  
First Principles ◽  
Insulator Transition ◽  
First Principles Calculations ◽  
Orbital Structure ◽  
Metal Insulator Transition ◽  
Metal Insulator

Using ultraviolet-infrared spectroscopy and first principles calculations, it is revealed that changes in the orbital structure can regulate the W-doped VO2 phase transition temperature.

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