Average Elastic Wave Velocities Research Articles

Elastic wave speeds, Debye temperature and microhardness of YX3 (X = In, Sn, Tl and Pb) intermetallic compounds

In the present work, we reviewed and report on the theoretical prediction of the longitudinal, transverse and average elastic wave veloci-ties, and the Debye temperature for some nonmagnetic YX3 (X = In, Sn, Tl, and Pb) intermetallic compounds with stable cubic AuCu3-type structure. The lattice parameters and the elastic constants used here are taken from the work of Abraham et al [1] using the general-ized gradient approximation (PBE-GGA). Our results are analyzed and compared with the available theoretical and experimental data, and in general a good agreement is found. The deviation between our value (224.4 K) of the Debye temperature θD for YSn3 material and the experimental one (210 K) is around 6.62%, while the deviation between our result (1401 m/s) of the transverse elastic wave velocity for YTl3 intermetallic material and the calculated one (1470 m/s) is about 4.93%. In addition the Young’s Modulus and Poisson’s Ratio of YX3 intermetallic compounds for the crystallographic planes (100), (110) and (111) are predicted.

Structural, electronic and elastic properties of FeCrAs Half-metallic ferromagnetic Half-Heusler Alloy: A First-Principles study

In this work, we employ full potential linearized augmented plane wave approach based on the density functional theory to calculate the structural, electronic, and elastic properties of FeCrAs Half-Heusler compound. For electron exchange, we have considered the most common Generalized Gradient Approximation (PBE-GGA and PBEsol-GGA), as exchange and correlation potential for investigating these properties. The half-metallic ferromagnetic behavior is confirmed by density of states and spin-polarized band structures analysis, which show that the FeCrAs has an indirect band-gap in the spin-down channel and a metallic behaviour in the spin-up channel. Furthermore, the elastic constants (Cij) and the related elastic moduli confirm their stability in the cubic phase and demonstrate their brittle nature. The Debye’s temperature along with compressional, Shear and average elastic wave velocities has also been calculated.[copyright information to be updated in production process]

Ab initio full-potential study of the fundamental properties of chalcopyrite semiconductors XPN2 (X = H, Cu)

This article reports the electronic, optical and structural properties of XPN2 (X = H, Cu) chalcopyrite semiconductors by implying the density functional theory (DFT) with full potential linearized augmented plane wave plus local orbitals (APW+lo) method. The calculated electronic and structural parameters such as energy band gap, anion displacement, tetragonal ratio and lattice parameters have shown good agreement with the previous experimental and theoretical results. The optical properties are described by calculating the absorption coefficients, dielectric function along with real and imaginary part of the dielectric function. Voigt-Reuss-Hill approximations are used to calculate the set of macroscopic elastic moduli including average elastic wave velocity, Young, shear and bulk moduli, Debye temperature and Poisson’s coefficient for chalcopyrite CuPN2 and HPN2. Finally, the semi-classical Bolzmann theory is applied with BolzTrap code to compute the transport properties such as thermal electrical conductivity, figure of merit and Seebeck coefficient for these materials.

A theoretical analysis of elastic and optical properties of half Heusler MCoSb (M=Ti, Zr and Hf)

Ab initio calculation of the Elastic and Optical properties of cubic half-Heusler compounds MCoSb (M = Ti, Zr and Hf) are reported using the FP-LAPW approach of the Density Functional Theory. Generalized Gradient Approximation was used as the exchange and correlation potential for investigating these properties. It was found that the Bulk modulus decreases with the increase in temperature and increases with the increase in pressure for all of the three Heusler compounds under study. The Debye's temperature along with compressional, Shear and average elastic wave velocities has also been calculated. The elastic results are compared with the available theoretical and experimental works. The optical investigation of the compounds shows high reflectivity at the infrared region of the photon energy. The imaginary part of the dielectric function reveled the optically non-metallic behavior of the MCoSb compounds, with optical band gap being around 1 eV.

Elastic Constants and Related Properties of Compressed Rocksalt CuX (X =Cl, Br): Ab Initio Study

Abstract First-principles calculations are performed to study the structural and elastic properties, sound velocities, and Debye temperature of rocksalt-structured copper monochloride (CuCl) and copper monobromide (CuBr). The structural parameters, elastic constants, longitudinal, transverse, and average elastic wave velocities, and the Debye temperature in the pressure range 10–20 GPa are successfully predicted and analysed. The variation of the elastic constants and bulk modulus as a function of pressure is found to be non-linear for CuCl and almost linear for CuBr. Based on the obtained values of the elastic constants, the bulk modulus, the isotropic shear modulus, Young’s modulus, Poisson’s ratio, and Pugh’s ratio of the aggregate materials are also investigated. The analysis of Poisson’s and Pugh’s ratios shows that these materials become ductile for pressures in the range 10–20 GPa. The evolution of the longitudinal sound velocity under pressure indicates the hardening of the corresponding phonons in both materials.

The structural, elastic, electronic and optical properties of orthorhombic FeX2 (X=S, Se, Te)

The structural, elastic, electronic and optical properties of FeX2 (X = S, Se, Te) with orthorhombic (space group Pnnm) structure have been investigated through the first-principles calculations. The calculated lattice constants, internal structure parameters and two kinds of Fe-X bond lengths agree reasonably with the experimental results. The corresponding single crystal elastic constants, polycrystalline elastic moduli, transverse, longitudinal, average elastic wave velocities, Debye temperature and minimum thermal conductivity decrease from FeS2 to FeTe2 while the elastic anisotropy index increases from FeS2 to FeTe2. All the three compounds show the brittle nature and covalent bonding. The orthorhombic FeX2 are non-magnetic semiconductors with indirect band gaps of 1.17eV, 0.64eV and 0.27eV, respectively. There have strong hybridizations between Fe-d orbitals and X-p orbitals. The real part and imaginary part of the dielectric function, refractive index and absorption coefficient are obtained and analyzed, the results show that the three compounds possess excellent absorption properties in ultraviolet and visible light regions. Both elastic properties and optical properties exhibit obvious anisotropy in the three compounds.

The structural, elastic and electronic properties of marcasite FeS2 under pressure

Employing the spin-polarized first-principles calculations, we have investigated the structural, elastic and electronic properties of marcasite FeS2 (m-FeS2) under pressure from 0 to 15 GPa. At zero pressure, the m-FeS2 is a non-magnetic semiconductor with an indirect band gap of 1.17 eV. The conduction band minimum (CBM) is mainly contributed by Fe-t2g states and a little by Fe-eg states, while the valence band maximum (VBM) is completely contributed by Fe-t2g states. The m-FeS2 is mechanically stable in the range of considered pressure. The c axis is the easiest to compress, while b axis is the hardest to compress. Both the brittle nature and covalent combination are observed for m-FeS2. With increasing pressure, the bulk modulus, shear modulus, Young's modulus, Poisson's ratio, anisotropy index AU, density, longitudinal, transverse, average elastic wave velocities, Debye temperature and minimum thermal conductivity of m-FeS2 increase smoothly, and both a small red shift for VBM and a small blue shift for CBM result in an increase of band gap.

Prediction study of structural, elastic and electronic properties of FeMP (M = Ti, Zr, Hf) compounds

Abstract First principles calculations are applied in the study of FeMP (M = Ti, Zr, Hf) compounds. We investigate the structural, elastic, mechanical and electronic properties by combining first-principles calculations with the CASTEP approach. For ideal polycrystalline FeMP (M = Ti, Zr, Hf) the shear modulus, Young’s modulus, Poisson’s ratio, elastic anisotropy indexes, Pugh’s criterion, elastic wave velocities and Debye temperature are also calculated from the single crystal elastic constants. The shear anisotropic factors and anisotropy are obtained from the single crystal elastic constants. The Debye temperature is calculated from the average elastic wave velocity obtained from shear and bulk modulus as well as the integration of elastic wave velocities in different directions of the single crystal.

Mechanical and Thermophysical Properties of Cubic Rock-Salt AlN Under High Pressure

Density functional theory, density functional perturbation theory, and the Debye model have been used to investigate the structural, elastic, sound velocity, and thermodynamic properties of AlN with cubic rock-salt structure under high pressure, yielding the equilibrium structural parameters, equation of state, and elastic constants of this interesting material. The isotropic shear modulus, Pugh ratio, and Poisson’s ratio were also investigated carefully. In addition, the longitudinal, transverse, and average elastic wave velocities, phonon contribution to the thermal conductivity, and interesting thermodynamic properties were predicted and analyzed in detail. The results demonstrate that the behavior of the elastic wave velocities under increasing hydrostatic pressure explains the hardening of the corresponding phonons. Based on the elastic stability criteria under pressure, it is found that AlN with cubic rock-salt structure is mechanically stable, even at pressures up to 100 GPa. Analysis of the Pugh ratio and Poisson’s ratio revealed that AlN with cubic rock-salt structure behaves in brittle manner.

Sound velocities and thermal properties of BeX (X=S, Se and Te) alkaline-earth chalcogenides

The sound velocities and some thermal properties of BeX (X=S, Se and Te) beryllium-chalcogenides large band gaps semiconductors have been estimated by employing some usual theoretical and emperical formulas. The lattice parameters and the elastic stiffness constants used here are taken from the literature. The longitudinal, transverse and average elastic wave velocities, the Debye temperature, the melting temperature, the thermal conductivity and the Grüneisen parameter are successfully predicted and analyzed in comparison with the available experimental and theoretical data. In general, our obtained results of these quantities agree well with the experimental and other theoretical data of the literature.

Elastic properties of cubic K2B12H12 from theoretical calculations

The elastic and mechanical properties of the cubic Fm3¯ K2B12H12 have been carried out based on first-principles calculations and elastic theory. The optimized structural parameters are in good agreement with available experimental and theoretical data. A serial of physical parameters are predicted for the first time, such as the single independent crystal elastic constants, polycrystalline elastic moduli, linear compressibility, and so on. It is found that the cubic Fm3¯ K2B12H12 is mechanically stable and ductile at zero temperature and zero pressure. The calculated anisotropic factors, directional dependent Young's modulus and Poisson's ratio varied with orientation show that the cubic Fm3¯ K2B12H12 is a rather weak anisotropy in its elastic behavior. In addition, the Debye temperature, average elastic wave velocity, as well as sound velocity in [100], [110] and [111] directions are also calculated.

Comment on “Pressure Induced Phase Transition, Elastic and Thermal Properties of Rare Earth Tellurides”

In the recent article ‘Pressure Induced Phase Transition, Elastic and Thermal Properties of Rare Earth Tellurides’ published by Rukmangad et al. (Trans Indian Inst Met 67(2):185–192, 2014), the high pressure phase transition, elastic and thermal properties of rare earth tellurides (RETe; RE = La, Ce, Pr, Sm and Eu) have been investigated by using a suitable inter-ionic potential with modified ionic charge (Zme) to include Coulomb screening effect. After studying their article, we have found some discrepancies in predicted crystal density, longitudinal, transverse and average elastic wave velocities, and Debye temperature data. The crystal density has been found multiplied by 2. Also the longitudinal, transverse and average elastic wave velocities and Debye temperature are different from our reexamined values. Although these discrepancies have no influence on the authors’ conclusion.

Anisotropic elastic and vibrational properties of Ru2B3 and Os2B3: a first-principles investigation

The structural, mechanical and lattice dynamical properties of Ru2B3 and Os2B3 have been investigated by using a first-principles method based on the density functional theory within the generalized gradient approximation. The single crystal elastic constants are numerically estimated using strain–stress approach. The polycrystalline aggregate elastic parameters are calculated from the single elastic constants via the Voigt–Reuss–Hill approximations. Subsequently, the ductility and brittleness are characterized with the estimation from Pugh’s rule (B/G) and Cauchy pressure. Additionally, the Debye temperature is calculated from the average elastic wave velocity obtained from bulk and shear moduli. The calculated parameters are consistent with the previous experimental and theoretical data. These borides are both mechanically and dynamically stable in the considered structure.

Comment on “Density functional investigation on electronic structure and elastic properties of BeX at high pressure”

In the article ‘Density functional investigation on electronic structure and elastic properties of BeX at high pressure’ published in Indian Journal of Physics (Pagare et al., Indian J Phys 90 271, 2016), Pagare et al. have investigated the structural, electronic, thermal, elastic and mechanical properties of BeX (X = Co, Ni, Cu and Pd) intermetallic compounds at high pressure. We believe that the authors committed an error during the calculation of the crystal density of these compounds which affects the calculation of some other physical properties such as longitudinal, transverse and average elastic wave velocities, and Debye temperature. In this comment, we have reexamined all data again by using the right formulae, and the values of the lattice parameters and the elastic constants obtained by Pagare et al. We have found that the crystal density values obtained by Pagare et al. have been multiplied by four and the values of longitudinal, transverse and average elastic wave velocities and Debye temperature have been divided by two.

Comment on "Ab Initio Study of the Structural, Elastic, Electronic and Optical Properties of Cu3N" [Materials Research. 2014;17(2):303-310

Recently, Rahmati et al., 1 have published a paper in Materials Research 2014; 17(2): 303-310. They have investigated the structural, elastic, electronic and optical properties of Cu3N in its phase cubic anti-ReO3 structure. But it is to be noted, that the numerical values of the density, the longitudinal (vl), transverse (vt) and average (vm) elastic wave velocities, and the Debye temperature obtained by Rahmati et al., 1 seem to be inaccurate. These errors are certainly due to the inaccuracy application of the formula used to calculate the density. In the present comment, we recalculated, and we gave the right numerical values of the density, the longitudinal (vl), transverse (vt) and average sound velocity (vm) and of the Debye temperature of Cu3N material, based on the lattice parameter and the elastic constants obtained in their work.

Comment on: Ab initio calculations of B2 type RHg (R = Ce,Pr,Eu and Gd) intermetallic compounds

In a recent article by Devi et al. [Eur. Phys. J. B 87, 268 (2014)], the structural, electronic, elastic and some thermal properties of B2 type RHg (R = Ce, Pr, Eu and Gd) intermetallic compounds have been studied by ab initio calculations. After the study of their article I found that there are some mistakes in predicted crystal density, longitudinal, transverse and average elastic wave velocities, and Debye temperature data. The crystal density has been found multiplied per 4. Also the longitudinal, transverse and average elastic wave velocities and Debye temperature are different from my reexamined values (all results represented by Devi et al. have been found divided per 2). Although these small mistakes do not influence their conclusion, it is better to correct them. In the present work, I reexamined all data again by using the right formulas, based on the lattice parameters and the elastic constants obtained in the work of Devi et al.

Brittle to Ductile Transition Dependence upon the Transition Pressure of MB_2 (M=Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W) Compounds

First principles calculations were performed to investigate the electronic and elastic properties of the group IV to group VI transition metal borides. As a result, the electronic bands and the density of states (DOS) at the Fermi level were obtained, also the independent elastic constants (C_(ij)) of hexagonal MB_2 (M=Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W) at zero pressure, the bulk moduli (B), the shear moduli (G), and the B/G ratio were also obtained. The brittle/ductile behavior of the group IV to group VI transition metal borides were evaluated and analyzed in comparison with the available data. The Debye temperature for ZrB_2 was calculated from the average elastic wave velocity obtained from the shear and bulk moduli. The calculated elastic properties are found to be in good agreement with the experimental values. The volume expansion coefficient _ versus temperature and pressure for ZrB_2 are discussed. The dependencies of the bulk, shear, Young's modulus, Poisson's ratio, and sound velocities V_l, V_t on the pressure P for ZrB_2 were also analyzed.

Structural, elastic, electronic and optical properties of the quaternary nitridogallate LiCaGaN2: First-principles study

First-principles density functional theory calculations were performed to predict some of the not yet explored physical properties of the monoclinic quaternary nitridogallate LiCaGaN2. The calculated lattice parameters, including the lattice constants, angle β and internal atomic coordinates, are in excellent agreement with the corresponding measured ones, proving the reliability of the chosen theoretical approach. The equation of state, pressure dependence of the lattice constants, unit cell volume, angle β and bond-lengths were explored in detail. The single-crystal and polycrystalline elastic constants and their pressure dependence were numerically estimated. The mechanical stability, ductility/brittleness, average elastic wave velocity, Debye temperature and elastic anisotropy were also assessed. The electronic structure and its evolution with external applied hydrostatic pressure were explored. The bonding character was demonstrated by calculating the site-projected density of states, charge density and effective Mulliken charges of all ions. The effective masses of the charge-carriers were numerically estimated. The complex dielectric function, refractive index, extinction coefficient, absorption coefficient, reflectivity and electron energy-loss function spectra were calculated for different polarizations of the incident light. Pressure dependence of the static dielectric constant, static refractive index and static reflectivity are also reported. To the best of our knowledge, this is the first attempt to explore the aforementioned physical properties for the title material.

Sound velocities and thermal properties of BX (X=As, Sb) compounds

The sound velocities and thermal properties of Boron-Arsenide (BAs) and Boron- Antimonide (BSb) materials have been predicted with the help of the empirical elastic constants which are taken from our previous work which is accepted to publication in International Journal of Scientific World. The longitudinal, transverse and average elastic wave velocities, the Debye temperature, the melting temperature, the thermal conductivity, the linear thermal expansion coefficient and finally the Gruneisen parameter are predicted and analyzed in comparison with the available theoretical data of the literature. Our obtained results are in general in very good agreement with the previous experimental and theoretical data of the literature.

Ab initio prediction of the structural, electronic, elastic and thermodynamic properties of the tetragonal ternary intermetallics XCu2Si2 (X = Ca, Sr)

Structural parameters, electronic structure, elastic constants and thermodynamic properties of the tetragonal ternary intermetallics CaCu2Si2 and SrCu2Si2 are investigated theoretically for the first time using the plane-wave ultra-soft pseudopotential method based on the density functional theory. The calculated equilibrium structural parameters agree well with the existing experimental data. Pressure dependence of the structural parameters is also explored. Analysis of the band structure, total and site-projected l-decomposed densities of states and valence charge distributions reveals the conducting character of both considered materials with a mixture of ionic-covalent chemical bonding character. Pressure dependences of the single-crystal elastic constants C ij for CaCu2Si2 and SrCu2Si2 are explored. The elastic wave velocities propagating along the principal crystallographic directions are numerically estimated. The elastic anisotropy is estimated and further illustrated by 3D-direction-dependent of the Young’s modulus. A set of some macroscopic elastic moduli, including the bulk, Young’s and shear moduli, Poisson’s coefficient, average elastic wave velocities and Debye temperature, were calculated for polycrystalline CaCu2Si2 and SrCu2Si2 from the C ij via the Voigt-Reuss-Hill approximations. Through the quasiharmonic Debye model, which takes into account the phonon effects, the temperature and pressure dependencies of the bulk modulus, unit cell volume, volume thermal expansion coefficient, Debye temperature and volume constant and pressure constant heat capacities of CaCu2Si2 and SrCu2Si2 are explored systematically in the ranges of 0–40 GPa and 0–1400 K.