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1
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A first-principles studies on TlX (X=P, As)

100%
Ciftci Y., Colakoglu K., Deligoz E.
Open Physics
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2008
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vol. 6
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issue 4
802-807
EN
We present an ab initio study of the structural, electronic and thermodynamic properties of TlX(X=P,As). The plane-wave pseudopotential approach to the density-functional theory within the LDA and GGA approximations implemented in VASP (Viena Ab-initio Simulation Package) is used. The calculated lattice parameter, elastic constants, and band structures are compared with other available theoretical results, and good agreement is obtained. In addition, we have calculated the transition pressure (P t) from zinc-blende (ZB) to (rock-salt) NaCl structures, and have examined some thermodynamic properties.
2
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The structural, elastic and thermodynamic properties of intermetallic compound CeGa2

100%
Çiftci Y., Çolakoǧlu K., Çoban C., Deligöz E.
Open Physics
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2012
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vol. 10
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issue 1
197-205
EN
The structural, elastic and thermodynamic characteristics of CeGa2 compound in the AlB2 (space group: P6/mmm) and the omega trigonal (space group: P-3m1) type structures are investigated using the methods of density functional theory within the generalized gradient approximation (GGA). The thermodynamic properties of the considered structures are obtained through the quasi-harmonic Debye model. The results on the basic physical parameters, such as the lattice constant, the bulk modulus, the pressure derivative of bulk modulus, the phase-transition pressure (P t) from P6/mmm to P-3m1 structure, the second-order elastic constants, Zener anisotropy factor, Poisson’s ratio, Young’s modulus, and the isotropic shear modulus are presented. In order to gain further information, the pressure and temperature-dependent behavior of the volume, the bulk modulus, the thermal expansion coefficient, the heat capacity, the entropy, Debye temperature and Grüneisen parameter are also evaluated over a pressure range of 0–6 GPa and a wide temperature range of 0–1800 K. The obtained results are in agreement with the available experimental and the other theoretical values.
3
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First-principles study of zinc-blende to rocksalt phase transition in BN

100%
Cui S., Feng W., Hu H., Feng Z.
Open Physics
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2010
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vol. 8
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issue 4
628-633
EN
The structural, electronic and elastic properties of the cubic boron nitride (BN) compound are investigated by a first-principle pseudopotential method. The calculations show that the structural phase transition from the zinc-blende(ZB) structure to the rocksalt (RS) structure occurs at a transition pressure of 1088 GPa and with a volume reduction of 3.1%. Both the ZB and RS structures of BN have indirect gaps, with energy gaps of 4.80 eV and 2.11 eV, respectively. The positive pressure derivative of the indirect band gap (Γ-X) energy for the the ZB phase and the predicted ultrahigh metallization pressure are attributed to the absence of d occupations in the valence bands. The increase of the shear modulus with increasing pressure implies that the lattice stability becomes higher when BN is compressed.
4
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Elastic Anisotropic and Thermodynamic Properties of Two BC₇ Phases

100%
Xing M., Li B., Yu Z., Chen Q.
Acta Physica Polonica A
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2017
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vol. 132
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issue 4
1340-1346
EN
The structural, elastic, anisotropic, and thermodynamic properties of P3m1-BC₇ and Pmm2-BC₇ have been studied in this paper utilizing first-principles calculations. In comparison with the elastic properties of Pmm2-BC₇, P3m1-BC₇ exhibits slightly higher values in bulk modulus and B/G, with similar values in shear modulus, the Young modulus, and the Poisson ratio. The calculated Pugh modulus ratio (B/G) and the Poisson ratio demonstrates P3m1-BC₇ from brittle to ductile at 93.60 and 93.73 GPa, respectively. Calculations of shear anisotropic factor, universal elastic anisotropy index, shear modulus, the Young modulus, and the Poisson ratio for BC₇ then demonstrate that Pmm2-BC₇ exhibits a larger elastic anisotropy than P3m1-BC₇. Quasi-harmonic Debye model is finally applied to investigate the Debye temperature, the coefficient of thermal expansion, heat capacity and Grüneisen parameter of Pmm2-BC₇ and P3m1-BC₇.
5
Content available remote

Structural, electronic and elastic properties of Ti2TlC, Zr2TlC and Hf2TlC

88%
Bouhemadou A.
Open Physics
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2009
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vol. 7
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issue 4
753-761
EN
Using First-principle calculations, we have studied the structural, electronic and elastic properties of M2TlC, with M = Ti, Zr and Hf. Geometrical optimization of the unit cell is in good agreement with the available experimental data. The effect of high pressures, up to 20 GPa, on the lattice constants shows that the contractions are higher along the c-axis than along the a axis. We have observed a quadratic dependence of the lattice parameters versus the applied pressure. The band structures show that all three materials are electrical conductors. The analysis of the site and momentum projected densities shows that bonding is due to M d-C p and M d-Tl p hybridizations. The M d-C p bonds are lower in energy and stiffer than M d-Tl p bonds. The elastic constants are calculated using the static finite strain technique. We derived the bulk and shear moduli, Young’s modulus and Poisson’s ratio for ideal polycrystalline M2TlC aggregates. We estimated the Debye temperature of M2TlC from the average sound velocity. This is the first quantitative theoretical prediction of the elastic properties of Ti2TlC, Zr2TlC, and Hf2TlC compounds that requires experimental confirmation.
6
Content available remote

First-Principles Calculations for Structural, Elastic, Electronic and Thermodynamic Properties of HfZn_{2} under Pressure

88%
Li G.-J., Shi L.-T., Hu C.-E., Cheng Y., Ji G.-F.
Acta Physica Polonica A
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2018
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vol. 133
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issue 5
1299-1306
EN
By using density functional theory within the Perdew-Burke-Ernzerhof generalized gradient approximation implemented in the VASP code, we study the structural, elastic, electronic, and thermodynamic properties of C15 Laves-phase compound HfZn_{2}. Comparing the lattice constants calculated from the Perdew-Burke-Ernzerhof generalized gradient approximation and local density approximation, we find that the former is in better agreement with the experimental data. The elastic constants of HfZn_{2} calculated by strain-stress method indicate that they keep stable up to 100 GPa. The bonding characteristics are discussed by analyzing the energy band structure, charge density distribution and charge density difference. Phonon dispersion curves and phonon density of states of HfZn_{2} at the different pressure are predicted for the first time. In addition, there is no imaginary frequency in the phonon band at different pressure, which also shows that HfZn_{2} is stable up to 100 GPa. Vibrational models are also illustrated based on phonon and group theory. The thermodynamic properties under high temperature and high pressure are calculated by different thermodynamic models. The heat capacity at constant pressure and low temperature calculated by quasi-harmonic approximation is more close to the measurement than that calculated by quasi-harmonic Debye models.
7
Content available remote

Elastic properties of (PbySn1−y )2P2S6 solid solutions

88%
Bilanych R., Yevych R., Kohutych A., Perechinskii S., Stoika I., Vysochanskii Y.
Open Physics
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2014
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vol. 12
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issue 9
611-614
EN
Elastic properties of (PbySn1−y )2P2S6 solid solutions were studied using Brillouin scattering technique. Different scattering geometries were used for sound velocities determination that make it possible to find all components of the stiffness tensor. The concentration dependencies of volume compressibility, the Grüneisen parameter and Debye temperature were investigated. The results obtained were used to analyze chemical bonding with substitution of tin by lead at room temperature in the crystals under consideration.
8
Content available remote

High temperature and pressure effects on the elastic properties of B2 intermetallics AgRE

88%
Liu L., Wu X., Li W., Wang R., Liu Q.
Open Physics
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2015
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vol. 13
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issue 1
EN
The high temperature and pressure effects on the elastic properties of the AgRE (RE=Sc, Tm, Er, Dy, Tb) intermetallic compounds with B2 structure have been performed from first principle calculations. For the temperature range 0-1000 K, the second order elastic constants for all the AgRE intermetallic compounds follow a normal behavior: they decrease with increasing temperature. The pressure dependence of the second order elastic constants has been investigated on the basis of the third order elastic constants. Temperature and pressure dependent elastic anisotropic parameters A have been calculated based on the temperature and pressure dependent elastic constants.
9
Content available remote

A Novel Theoretical Study of Elastic and Electronic Properties of M₂CdC (M = Zr, Hf, and Ta) MAX Phases

75%
Mebrek M., Mokaddem A., Doumi B., Yakoubi A., Mir A.
Acta Physica Polonica A
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2018
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vol. 133
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issue 1
76-81
EN
In this study, we have investigated the structural, electronic, and elastic properties of the M₂CdC (M = Ta, Zr, and Hf) MAX phases, using the first-principle methods based on the density functional theory. The calculated formation energies revealed that these compounds are thermodynamically stable in the hexagonal MAX phase. The stability is confirmed by the elastic constants and the conditions of mechanical stability criterion. Also, we have determined the bulk and shear modules of the Young modulus and the Poisson coefficient. The band structures indicate that the three materials are electrically conductive. The chemical bond in M₂CdC is covalent-ionic in nature with the presence of metallic character. For the density of states the hybridization peak between M d and C p occurs in the lower energy range. We have found that there is no gap for these materials due to the existence of a maximum peak of DOS around Fermi level.
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