scholarly journals New Zirconium Diboride Polymorphs—First-Principles Calculations

Materials ◽  
2020 ◽  
Vol 13 (13) ◽  
pp. 3022 ◽  
Author(s):  
Marcin Maździarz ◽  
Tomasz Mościcki
Keyword(s):  
Thermodynamic Properties ◽  
First Principles ◽  
Density Functional ◽  
Formation Enthalpy ◽  
Density Functional Theory Calculations ◽  
Zirconium Diboride ◽  
Point Of View ◽  
Phonon Modes ◽  
Functional Theory ◽  
Space Group

Two new hypothetical zirconium diboride (ZrB 2 ) polymorphs: (hP6-P6 3 /mmc-space group, no. 194) and (oP6-Pmmn-space group, no. 59), were thoroughly studied under the first-principles density functional theory calculations from the structural, mechanical and thermodynamic properties point of view. The proposed phases are thermodynamically stable (negative formation enthalpy). Studies of mechanical properties indicate that new polymorphs are less hard than the known phase (hP3-P6/mmm-space group, no. 191) and are not brittle. Analysis of phonon band structure and density of states (DOS) also show that the phonon modes have positive frequencies everywhere and the new ZrB 2 phases are not only mechanically but also dynamically stable. The estimated acoustic Debye temperature, Θ D , for the two new proposed ZrB 2 phases is about 760 K. The thermodynamic properties such as internal energy, free energy, entropy and constant-volume specific heat are also presented.

Graphene bandgap induced by ferroelectric Pca21 HfO2 substrates: a first-principles study

2019 ◽  
Vol 21 (27) ◽  
pp. 15001-15006 ◽  
Author(s):  
George Alexandru Nemnes ◽  
Daniela Dragoman ◽  
Mircea Dragoman
Keyword(s):  
Density Functional Theory ◽  
Electronic Properties ◽  
First Principles ◽  
Density Functional ◽  
Orthorhombic Phase ◽  
Density Functional Theory Calculations ◽  
Functional Theory ◽  
Space Group ◽  
First Principles Study

The electronic properties of graphene on top of ferroelectric HfO2 substrates in an orthorhombic phase with space group Pca21 are investigated using density functional theory calculations.

scholarly journals Structural, Mechanical and Thermodynamic Properties under Pressure Effect of Rubidium Telluride: First Principle Calculations

2017 ◽  
Vol 62 (2) ◽  
pp. 865-871 ◽  
Author(s):  
K. Bidai ◽  
M. Ameri ◽  
I. Ameri ◽  
D. Bensaid ◽  
A. Slamani ◽  
...  
Keyword(s):  
Thermodynamic Properties ◽  
First Principles ◽  
Density Functional ◽  
Poisson Ratio ◽  
Density Functional Theory Calculations ◽  
Lattice Parameter ◽  
Thermodynamic Quantities ◽  
Generalized Gradient ◽  
Functional Theory ◽  
Equilibrium Lattice Parameter

AbstractFirst-principles density functional theory calculations have been performed to investigate the structural, elastic and thermodynamic properties of rubidium telluride in cubic anti-fluorite (anti-CaF2-type) structure. The calculated ground-state properties of Rb2Te compound such as equilibrium lattice parameter and bulk moduli are investigated by generalized gradient approximation (GGA-PBE) that are based on the optimization of total energy. The elastic constants, Young’s and shear modulus, Poisson ratio, have also been calculated. Our results are in reasonable agreement with the available theoretical and experimental data. The pressure dependence of elastic constant and thermodynamic quantities under high pressure are also calculated and discussed.

Understanding the advantage of hexagonal WO3 as an efficient photoanode for solar water splitting: a first-principles perspective

2016 ◽  
Vol 4 (29) ◽  
pp. 11498-11506 ◽  
Author(s):  
Taehun Lee ◽  
Yonghyuk Lee ◽  
Woosun Jang ◽  
Aloysius Soon
Keyword(s):  
Density Functional Theory ◽  
Band Gap ◽  
Water Splitting ◽  
Anode Material ◽  
First Principles ◽  
Density Functional ◽  
Density Functional Theory Calculations ◽  
Good Alternative ◽  
Functional Theory ◽  
Solar Water Splitting

Using first-principles density-functional theory calculations, we investigate the advantage of using h-WO3 (and its surfaces) over the larger band gap γ-WO3 phase for the anode in water splitting. We demonstrate that h-WO3 is a good alternative anode material for optimal water splitting efficiencies.

Probing the electronic structures of Con (n = 1–5) clusters on γ-Al2O3 surfaces using first-principles calculations

2017 ◽  
Vol 19 (5) ◽  
pp. 3679-3687 ◽  
Author(s):  
Tao Yang ◽  
Masahiro Ehara
Keyword(s):  
Density Functional Theory ◽  
First Principles ◽  
Electronic Structures ◽  
Density Functional ◽  
Density Functional Theory Calculations ◽  
First Principles Calculations ◽  
Functional Theory

Using density functional theory calculations, we discussed the geometric and electronic structures and nucleation of small Co clusters on γ-Al2O3(100) and γ-Al2O3(110) surfaces.

scholarly journals Strain Conditions for the Inverse Heusler Type Fully Compensated Spin-Gapless Semiconductor Ti2MnAl: A First-Principles Study

Materials ◽  
2018 ◽  
Vol 11 (11) ◽  
pp. 2091 ◽  
Author(s):  
Tie Yang ◽  
Liyu Hao ◽  
Rabah Khenata ◽  
Xiaotian Wang
Keyword(s):  
Thermodynamic Properties ◽  
First Principles ◽  
Density Functional ◽  
Theoretical Study ◽  
Debye Model ◽  
Pressure Effects ◽  
First Principles Calculation ◽  
Strain Condition ◽  
Functional Theory ◽  
Future Work

In this work, we systematically studied the structural, electronic, magnetic, mechanical and thermodynamic properties of the fully compensated spin-gapless inverse Heusler Ti2MnAl compound under pressure strain condition by applying the first-principles calculation based on density functional theory and the quasi-harmonic Debye model. The obtained structural, electronic and magnetic behaviors without pressure are well consistent with previous studies. It is found that the spin-gapless characteristic is destroyed at 20 GPa and then restored with further increase in pressure. While, the fully compensated ferromagnetism shows a better resistance against the pressure up to 30 GPa and then becomes to non-magnetism at higher pressure. Tetragonal distortion has also been investigated and it is found the spin-gapless property is only destroyed when c/a is less than 1 at 95% volume. Three independent elastic constants and various moduli have been calculated and they all show increasing tendency with pressure increase. Additionally, the pressure effects on the thermodynamic properties under different temperature have been studied, including the normalized volume, thermal expansion coefficient, heat capacity at constant volume, Grüneisen constant and Debye temperature. Overall, this theoretical study presents a detailed analysis of the physical properties’ variation under strain condition from different aspects on Ti2MnAl and, thus, can provide a helpful reference for the future work and even inspire some new studies and lead to some insight on the application of this material.

Preliminary First Principles Study Of Hf and Zr Aluminates as Replacement High-k Dielectrics

2001 ◽  
Vol 670 ◽  
Author(s):  
Michael Haverty ◽  
Atsushi Kawamoto ◽  
Gyuchang Jun ◽  
Kyeongjae Cho ◽  
Robert Dutton
Keyword(s):  
Density Functional Theory ◽  
Dielectric Constant ◽  
Bulk Density ◽  
First Principles ◽  
Density Functional ◽  
Density Functional Theory Calculations ◽  
Conduction Band Edge ◽  
Functional Theory ◽  
Trade Off ◽  
High K

ABSTRACTBulk Density Functional Theory calculations were performed on Hf and Zr substitutions for Al in κ-alumina. The lowest energy configuration found was an octahedrally coordinated Zr site. Zr dissolution was favorable with an enthalpy of -2eV/unit cell for forming Al1.875Zr0.125O3 from pure Zr and κ-alumina. Hf and Zr substitution for Al atoms introduced empty d-states below the conduction band edge reducing the Eg of pure κ-alumina (7.5eV) to 6.4-5.9eV. The edge of the valence band however remained fixed by the O p-state character. The substitution of Hf and Zr into the alumina structure may lead to a higher dielectric constant, but will also reduce Eg and result in a trade off in tunneling currents in devices.

First-Principles Analysis on Interaction between Dopant (Ga, Sb) and Contamination Metal Atoms in Ge Crystals

2013 ◽  
Vol 205-206 ◽  
pp. 417-421
Author(s):  
Tatsunori Yamato ◽  
Koji Sueoka ◽  
Takahiro Maeta
Keyword(s):  
First Principles ◽  
Density Functional ◽  
Density Functional Theory Calculations ◽  
Binding Energies ◽  
Functional Theory ◽  
Substitutional Site ◽  
Metal Impurities ◽  
Metal Atoms ◽  
Total Energies ◽  
Group 3

The lowest energetic configurations of metal impurities in 4throw (Sc - Zn), 5throw (Y - Cd) and 6throw (Hf - Hg) elements in Ge crystals were determined with density functional theory calculations. It was found that the substitutional site is the lowest energetic configuration for most of the calculated metals in Ge. The most stable configurations of dopant (Ga, Sb) - metal complexes in Ge crystals were also investigated. Following results were obtained. (1) For Ga dopant, 1st neighbor T-site is the most stable for metals in group 3 to 7 elements while substitutional site next to Ga atom is the most stable for metals in group 8 to 12 elements. (2) For Sb dopant, substitutional site next to Sb atom is the most stable for all calculated metals. Binding energies of the interstitial metalMiwith the substitutional dopantDswere obtained by the calculated total energies. The calculated results for Ge were compared with those for Si.

Thermodynamic Properties of CaSiO3 Perovskite at High Pressure and High Temperature

2009 ◽  
Vol 64 (5-6) ◽  
pp. 399-404 ◽  
Author(s):  
Zi-Jiang Liu ◽  
Xiao-Ming Tan ◽  
Yuan Guo ◽  
Xiao-Ping Zheng ◽  
Wen-Zhao Wu
Keyword(s):  
Thermodynamic Properties ◽  
First Principles ◽  
Density Functional ◽  
High Pressures ◽  
Local Density ◽  
Harmonic Approximation ◽  
Debye Model ◽  
Functional Theory ◽  
Casio3 Perovskite ◽  
First Time

The thermodynamic properties of tetragonal CaSiO3 perovskite are predicted at high pressures and temperatures using the Debye model for the first time. This model combines the ab initio calculations within local density approximation using pseudopotentials and a plane wave basis in the framework of density functional theory, and it takes into account the phononic effects within the quasi-harmonic approximation. It is found that the calculated equation of state is in excellent agreement with the observed values at ambient condition. Based on the first-principles study and the Debye model, the thermal properties including the Debye temperature, the heat capacity, the thermal expansion and the entropy are obtained in the whole pressure range from 0 to 150 GPa and temperature range from 0 to 2000 K.

scholarly journals Oxygen Vacancy Induced Magnetism in Anti-Perovskite Topological Dirac Semimetal Ba3SnO

2021 ◽  
Author(s):  
Javaria Batool ◽  
Syed Muhammad Alay-e-Abbas ◽  
Gustav Johansson ◽  
Waqas Zulfiqar ◽  
Muhammad Arsam Danish ◽  
...  
Keyword(s):  
Density Functional Theory ◽  
Oxygen Vacancy ◽  
Electronic Properties ◽  
Thermodynamic Stability ◽  
First Principles ◽  
Density Functional ◽  
Density Functional Theory Calculations ◽  
Vacancy Defect ◽  
Functional Theory ◽  
Dirac Semimetal

The thermodynamic, structural, magnetic and electronic properties of pristine and intrinsic vacancy defect containing topological Dirac semimetal Ba3SnO are studied using first-principles density functional theory calculations. The thermodynamic stability of...

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