First-principles study on structural, elastic and thermal properties of γ-TiAl and α2-Ti3Al phases in TiAl-based alloy under high pressure

2017 ◽  
Vol 31 (11) ◽  
pp. 1750079 ◽  
Author(s):  
Chaoyan Zhang ◽  
Hua Hou ◽  
Yuhong Zhao ◽  
Xiaomin Yang ◽  
Yaqiong Guo
Keyword(s):  
High Pressure ◽  
Thermal Properties ◽  
Density Functional ◽  
Theoretical Data ◽  
Debye Model ◽  
Functional Theory ◽  
The Density Functional Theory ◽  
Two Phases ◽  
Calculated Equilibrium ◽  
Good Agreement

The structural, elastic and thermal properties of [Formula: see text]-TiAl and [Formula: see text]-Ti3Al phases in the TiAl-based alloy under pressure were reported using CASTEP program based on the density functional theory. The calculated equilibrium parameters and elastic constants are in good agreement with experimental and the available theoretical data. The results indicate that under the same pressure, the [Formula: see text] phase in the direction along [Formula: see text]-axis is easier to be compressed than the [Formula: see text] phase, while the compression along [Formula: see text]-axis of [Formula: see text] phase is larger than that of [Formula: see text] phase; when the pressure is below 20 GPa, both the two phases are elastically stable, but the [Formula: see text] phase have higher shear modulus and Young’s modulus, and the [Formula: see text] phase has better ductility and plasticity. Debye temperature, bulk modulus, thermal expansion coefficient and heat capacity of the [Formula: see text] phase and [Formula: see text] phase under high pressure and high temperature were also successfully calculated and compared using the quasi-harmonic Debye model in the present work.

scholarly journals Structural, elastic, electronic and thermal properties of InAs: A study of functional density

2017 ◽  
Vol 26 (46) ◽  
Author(s):  
Víctor Mendoza-Estrada ◽  
Melissa Romero-Baños ◽  
Viviana Dovale-Farelo ◽  
William López-Pérez ◽  
Álvaro González-García ◽  
...  
Keyword(s):  
Thermal Properties ◽  
Density Functional ◽  
Experimental Studies ◽  
Debye Model ◽  
Band Gap Energy ◽  
Functional Theory ◽  
Zinc Blende ◽  
The Density Functional Theory ◽  
The Stability ◽  
Experimental Values

In this research, first-principles calculations were carried out within the density functional theory (DFT) framework, using LDA and GGA, in order to study the structural, elastic, electronic and thermal properties of InAs in the zinc-blende structure. The results of the structural properties (a, B0, ) agree with the theoretical and experimental results reported by other authors. Additionally, the elastic properties, the elastic constants (C11, C12 and C44), the anisotropy coefficient (A) and the predicted speeds of the sound ( , , and ) are in agreement with the results reported by other authors. In contrast, the shear modulus (G), the Young's modulus (Y) and the Poisson's ratio (v) show some discrepancy with respect to the experimental values, although, the values obtained are reasonable. On the other hand, it is evident the tendency of the LDA and GGA approaches to underestimate the value of the band-gap energy in semiconductors. The thermal properties (V, , θD yCV) of InAs, calculated using the quasi-harmonic Debye model, are slightly sensitive as the temperature increases. According to the stability criteria and the negative value of the enthalpy of formation, InAs is mechanically and thermodynamically stable. Therefore, this work can be used as a future reference for theoretical and experimental studies based on InAs.

First-principle-based structural and thermodynamic parameters of Ni–Al intermetallic compounds under different pressures and temperatures

2021 ◽  
pp. 2150124
Author(s):  
Shabir Ali ◽  
Taihong Huang ◽  
Peng Song ◽  
Syed Hatim Shah ◽  
Rawaid Ali ◽  
...  
Keyword(s):  
Bulk Modulus ◽  
Intermetallic Compounds ◽  
Thermodynamic Parameters ◽  
Density Functional ◽  
Debye Model ◽  
First Principles Calculation ◽  
Functional Theory ◽  
The Density Functional Theory ◽  
Temperature Ranges ◽  
Good Agreement

The structural and temperature reliance manner of the thermodynamic parameters of Ni–Al intermetallic compounds with different pressures is comprehensively studied by executing first-principles calculation using the density functional theory (DFT). The calculated optimized volume and bulk modulus are in good agreement with the experimental and theoretical results at zero pressure. Quasi-harmonic Debye model is adopted to find out the bulk modulus, volumetric thermal expansion coefficient, Debye temperature, Gibbs free energy and enthalpy of Ni–Al intermetallic compounds in different pressure ranges from 0 MPa to 600 MPa and temperature ranges from 0 K to 1200 K. Additionally, special attention is paid to calculate the mutual relationships between the thermodynamic parameters with different pressures and temperatures.

scholarly journals Structural, Elastic and Thermal Properties of Lanthanide Monoantimonides

2018 ◽  
Vol 2 (1) ◽  
Keyword(s):  
Thermal Properties ◽  
Density Functional ◽  
Theoretical Data ◽  
Full Potential ◽  
Functional Theory ◽  
Augmented Plane Wave ◽  
Cauchy Pressure ◽  
The Density Functional Theory ◽  
G Ratio ◽  
Linearized Augmented Plane Wave

Structural, elastic and thermal properties of lanthanide monoantimonides LnSb (Ln = La, Ce, Pr, Nd, Sm, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu) compounds have been studied theoretically using full potential linearized augmented plane wave plus local orbitals (FP-LAPW + lo) method within the density functional theory. The structural properties are investigated by using GGA-PBEsol scheme. We calculated bulk modulus, shear modulus, Young’s modulus, anisotropic ratio, Kleinman parameters, Poisson’s ratio, Lame’s co-efficient, sound velocities for shear and longitudinal waves, and Debye temperature. We also predict the Cauchy pressure and B/G ratio in order to explore the ductile and brittle behaviors of these compounds.Our results are in good agreement with available experimental and other theoretical data and also provide predictions where no experimental or theoretical results are available.

Theoretical study of protactinium at high pressure

2005 ◽  
Vol 893 ◽  
Author(s):  
Börje Johansson ◽  
Sa Li ◽  
Eyvaz Eyvaz ◽  
Rajeev Ahuja
Keyword(s):  
High Pressure ◽  
Density Functional ◽  
The Body ◽  
Generalized Gradient ◽  
Functional Theory ◽  
Fitting Procedure ◽  
A Value ◽  
The Density Functional Theory ◽  
Murnaghan Equation ◽  
Good Agreement

AbstractWe have studied the crystal structure of Pa metal under high pressure by means of first-principles calculations based on the density functional theory (DFT) using the generalized gradient approximation (GGA). The body centered tetragonal (bct) to orthorhombic (α-U) phase transition was calculated to take place at 29 GPa and with a volume change of 1.3%. The calculated c/a for the bct phase reaches the ideal c/a value (0.816) at around 50 GPa. A bulk modulus of 113 GPa was derived from a Murnaghan equation of state (EOS) fitting procedure. Our results are in general good agreement with recent experiment performed by Haire et al. [Phys. Rev. B 67, 134101 (2003)]. We have also calculated the phonon spectrum for fcc, bct and bcc Pa. The latter gives imaginary frequencies showing the low temperature instability of this crystallographic phase for Pa.

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.

Pressure effect on the structural, phonon, elastic and thermodynamic properties of L12phase RH3TA: First-principles calculations

2018 ◽  
Vol 32 (14) ◽  
pp. 1850169
Author(s):  
Leini Wang ◽  
Zhang Jian ◽  
Wei Ning
Keyword(s):  
Thermodynamic Properties ◽  
Density Functional ◽  
Harmonic Approximation ◽  
Debye Model ◽  
Approximation Model ◽  
Functional Theory ◽  
The Density Functional Theory ◽  
Relationship Of ◽  
G Ratio ◽  
Wide Pressure

The phonon, elastic and thermodynamic properties of L12phase Rh3Ta have been investigated by the density functional theory (DFT) approach combined with the quasi-harmonic approximation model. The results of the phonon band structure show that L12phase Rh3Ta possesses dynamical stability in the pressure range from 0–80 GPa due to the absence of imaginary frequencies. The pressure dependences with the elastic constants C[Formula: see text], shear modulus G, bulk modulus B, Young’s modulus Y, Poisson’s ratio and B/G ratio have been analyzed. The results of the elastic properties studies show that L12phase Rh3Ta compound is mechanically stable and possesses a higher hardness, improved ductility and plasticity under higher pressures. The pressure and temperature relationship of the thermodynamic properties, such as the Debye temperature [Formula: see text], heat capacity C[Formula: see text], thermal expansion coefficient [Formula: see text] and the Grüneisen parameter [Formula: see text] are predicted by the quasi-harmonic Debye model in a wide pressure (0–80 GPa) and temperature (0–750 K) ranges.

scholarly journals Thermal properties of cubic zincblende thallium-phosphide from quasi-harmonic Debye model approximation

2017 ◽  
Vol 5 (1) ◽  
pp. 14 ◽  
Author(s):  
Salah Daoud
Keyword(s):  
High Pressure ◽  
Thermal Properties ◽  
Bulk Modulus ◽  
Unit Cell Volume ◽  
Theoretical Data ◽  
Debye Model ◽  
Zero Temperature ◽  
Isothermal Bulk Modulus ◽  
Model Approximation ◽  
First Order

The thermal properties of cubic zincblende (B3) thallium - phosphide (TlP) compound under high pressure up to 12 GPa have been studied using the quasi-harmonic Debye model approximation. The relative unit cell volume, the isothermal bulk modulus, the first order derivative isothermal bulk modulus, the Debye temperature and the Grüneisen parameter are studied at zero-temperature and at standard ambient temperature (298 K) respectively. Our obtained values of the different previous quantities are in general in agreement compared to other theoretical data of the literature.

A combined study of the equation of state of monazite-type lanthanum orthovanadate usingin situhigh-pressure diffraction andab initiocalculations

2014 ◽  
Vol 70 (3) ◽  
pp. 533-538 ◽  
Author(s):  
Olga Ermakova ◽  
Javier López-Solano ◽  
Roman Minikayev ◽  
Stefan Carlson ◽  
Agata Kamińska ◽  
...  
Keyword(s):  
Equation Of State ◽  
Density Functional ◽  
Room Temperature ◽  
Theoretical Data ◽  
Perfect Agreement ◽  
Functional Theory ◽  
Compression Direction ◽  
The Density Functional Theory ◽  
Murnaghan Equation

Lanthanum orthovanadate (LaVO4) is the only stable monazite-type rare-earth orthovanadate. In the present paper the equation of state of LaVO4is studied usingin situhigh-pressure powder diffraction at room temperature, andab initiocalculations within the framework of the density functional theory. The parameters of a second-order Birch–Murnaghan equation of state,i.e.those fitted to the experimental and theoretical data, are found to be in perfect agreement – in particular, the bulk moduli are almost identical, with values of 106 (1) and 105.8 (5) GPa, respectively. In agreement with recent reported experimental data, the compression is shown to be anisotropic. Its nature is comparable to that of some other monazite-type compounds. The softest compression direction is determined.

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