scholarly journals optPBE-vdW density functional theory study of liquid water and pressure-induced structural evolution in ice Ih

2017 ◽  
Vol 95 (11) ◽  
pp. 1205-1211 ◽  
Author(s):  
Xue Yong ◽  
John S. Tse ◽  
Niall J. English
Keyword(s):  
Density Functional ◽  
Structural Parameters ◽  
Structural Evolution ◽  
Hexagonal Structure ◽  
Density Functional Theory Study ◽  
Phonon Modes ◽  
Functional Theory ◽  
Exchange Correlation ◽  
Crystal Transformation ◽  
Non Local

The accuracy of several local and non-local van der Waals (vdW) corrected exchange correlation functionals on the description of the effect of pressure on ice has been investigated. In a preliminary survey, the non-local vdW correction used in conjunction with the optPBE functional was shown to provide the best overall agreement on the structural parameters of ice Ih with experiments. More importantly, this combination reproduced correctly the recently observed crystal → crystal transformation in ice Ih at 80 K prior to amorphisation. The predicted transition pressure of 1.9 GPa is somewhat higher, showing that the current generation of vdW functionals are still not sufficiently accurate for the ice system. The existence of an intermediate crystalline state with a shear-hexagonal structure confirms the earlier prediction that the collapse of crystalline structure under compression originates from the softening of phonon modes in ice Ih’s basal plane.

Theoretical Investigations on Mechanical Stability and Electronic Structure of NbN under Pressures

2011 ◽  
Vol 90-93 ◽  
pp. 1264-1271
Author(s):  
Xiao Feng Li ◽  
Jun Yi Du
Keyword(s):  
Debye Temperature ◽  
Density Functional ◽  
Mechanical Stability ◽  
Structural Parameters ◽  
Theoretical Data ◽  
Hexagonal Structure ◽  
Functional Theory ◽  
Theoretical Investigations ◽  
Crystallographic Structures ◽  
Good Agreement

The ground structure, elastic and electronic properties of several phases of NbN are determined based on ab initio total-energy calculations within the framework of density functional theory. Among the five crystallographic structures that have been investigated, the hexagonal phases have been found to be more stable than the cubic ones. The calculated equilibrium structural parameters are in good agreement with the available experimental results. The elastic constants of five structures in NbN are calculated, which are in consistent with the obtained theoretical and experimental data. The corresponding Debye temperature and elastic ansitropies are also obtained. The Debye temperature of NbN in various structures consistent with available experimental and theoretical data, in which the Debye temperature of δ-NbN is highest. The anisotropies of ZB-NbN, NaCl-NbN, CsCl-NbN gradually increases. For hexagonal structure, the anisotropies of ε-NbN are stronger than that of δ-NbN. The electronic structures of NbN under pressure are investigated. It is found that NbN have metallization and the hybridizations of atoms in NbN under pressure become stronger.

Oxides, Silicides, and Silicates of Zirconium and Hafnium; Density Functional Theory Study

2002 ◽  
Vol 716 ◽  
Author(s):  
Maciej Gutowski ◽  
John E. Jaffe ◽  
Chun-Li Liu ◽  
Matt Stoker ◽  
Anatoli Korkin
Keyword(s):  
Density Functional Theory ◽  
Density Functional ◽  
Gate Dielectric ◽  
Density Functional Theory Calculations ◽  
Heat Of Formation ◽  
Density Functional Theory Study ◽  
Functional Theory ◽  
Exchange Correlation ◽  
The Difference ◽  
Constituent Elements

AbstractIt is known that the chemistries of hafnium and zirconium are more nearly identical than for any other two congeneric elements. Thus, both zirconia and hafnia, with the dielectric constant K > 20, have emerged as potential replacements for silica (K = 3.9) as a gate dielectric. We report an important difference between the zirconia/Si and hafnia/Si interfaces based on density functional theory calculations with the Perdew-Wang 91 exchange-correlation functional on the oxides, silicides, and silicates of Zr and Hf. The zirconia/Si interface has been found to be unstable with respect to formation of silicides whereas the hafnia/Si interface is stable. The difference between the two interfaces results from the fact that HfO2 is more stable than ZrO2 (i.e. has a larger heat of formation from its constituent elements) by more than 53 kJ/mol. The hafnium silicides, on the other hand, are less stable than zirconium silicides by ca. 20 kJ/mol.

scholarly journals Structural and piezoelectric coefficients of AlP under pressure

2018 ◽  
Vol 6 (2) ◽  
pp. 53
Author(s):  
Salah Daoud ◽  
Rabie Mezouar ◽  
Abdelfateh Benmakhlouf
Keyword(s):  
Density Functional ◽  
Structural Parameters ◽  
Generalized Gradient ◽  
Aluminum Phosphide ◽  
Functional Theory ◽  
Exchange Correlation ◽  
Generalized Gradient Approximation ◽  
Zinc Blende ◽  
Density Functional Perturbation Theory ◽  
The Density Functional Theory

The present work aims to investigate the structural parameters and the piezoelectric coefficients of cubic zinc-blende Aluminum phosphide (AlP) under high pressure up to 21 GPa, using plane wave-pseudopotential (PW-PP) approach in the framework of the density functional theory (DFT) and the density functional perturbation theory (DFPT) with the generalized gradient approximation (GGA) for the exchange-correlation functional. The results obtained are analyzed and compared with other data of the literature. The structural parameters and the piezoelectric coefficients calculated here agree well with other data of the literature. We found also that both the direct and converse piezoelectric coefficients increase with increasing pressure up to 21 GPa. 

Structural evolution, electronic and magnetic manners of small rhodium Rhn+/− (n = 2–8) clusters: a detailed density functional theory study

RSC Advances ◽  
2016 ◽  
Vol 6 (9) ◽  
pp. 6946-6959 ◽  
Author(s):  
Abhijit Dutta ◽  
Paritosh Mondal
Keyword(s):  
Density Functional Theory ◽  
Magnetic Properties ◽  
Electronic Structure ◽  
Density Functional ◽  
Structural Evolution ◽  
Density Functional Theory Study ◽  
Functional Theory ◽  
Magic Cluster

We have evaluated the stable electronic structure and magnetic properties of all neutral and ionic Rhn (n = 2–8) clusters using density functional theory. This study reveals that Rh4 is the magic cluster based on the calculated reactivity parameters.

scholarly journals Spinelectronic investigation of the quaternary vanadium fluoride Rb2NaVF6: Ab-initio method

2020 ◽  
Vol 66 (5 Sept-Oct) ◽  
pp. 604
Author(s):  
M. Berber ◽  
N. Bouzouira ◽  
H. Abid ◽  
A. Boudali ◽  
H. Moujri
Keyword(s):  
Density Functional ◽  
Structural Parameters ◽  
Magnetic Moments ◽  
Generalized Gradient ◽  
Functional Theory ◽  
Half Metallic ◽  
Exchange Correlation ◽  
Spin Polarized ◽  
Higher Temperature ◽  
Good Agreement

In this study, we have investigated the structural, electronic, and magnetic properties of the Rb2NaVF6 compound. We have performed our calculations by the use of first-principle methods based on spin-polarized density functional theory, where the electronic exchange-correlation potential is treated by the generalized gradient approximation GGA- PBEsol coupled with the improved TB-mBJ approach. The calculated structural parameters of Rb2NaVF6 are in good agreement with the available experimental data. Rb2NaVF6 exhibits a half-metallic ferromagnetic feature with a spin polarization of 100 % at the Fermi level and a direct large half-metallic gap of 3.582 eV. The total magnetic moments are 2 μB. This material is half-metallic ferromagnets, and it can be potential candidates for spintronics applications at a higher temperature.

scholarly journals First Insight on Electronic Structure, Structural Stability, Dynamical and Mechanical Properties of Two-Dimensional LaAuo3.

2019 ◽  
pp. 1-17
Keyword(s):  
Electronic Structure ◽  
Structural Stability ◽  
Density Functional ◽  
Structural Parameters ◽  
Hybrid Functional ◽  
Functional Theory ◽  
Exchange Correlation ◽  
Fundamental Understanding ◽  
Covalent Interactions ◽  
Detailed Chemical

Abstract The electronic structure, structural stability, dynamical, mechanical, ionic conductivity, optical properties, and bonding nature of LaAuO3 are investigated by means of first principle calculations based on density functional theory (DFT). The equilibrium structural parameters are obtained within the general gradient approximation (GGA), in particular using the Perdew Burke Ernzerhof (PBE) exchange correlation functional, while the electronic structure is investigated using the screened hybrid functional proposed by Heyd, Scuseria and Ernzerhof (HSE06). The computed band gaps values and the nature of the electronic structure are found to be similar to ZnO and GaN. The detailed chemical bonding analysis reveals the nature of bonds: La–O exhibit mainly ionic interaction, whereas Au-O exhibits iono-covalent interactions. This study provides a fundamental understanding of the structural, mechanical, and electronic properties of LaAuO3.

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