La revue : Superlattices and Microstructures
Domaine : Physics
Mots Clés : Antiperovskite; FP-APW+LO; Magnetic properties; Elastic properties; Electronic band-structure; Thermoelectric properties
Auteur : T. Seddik, GÖKAY Uğur, F Soyalp, R Khenata, Deo Prakash, IV Kityk, Saleem Ayez Khan, A Bouhemadou, S Bin-Omran, DP Rai, KD Verma
Issn : 0749-6036 Eissn : vol : 109, Num : , pp : 1-12
Date de publication : 2016-08-25
Résume : In this work, we have theoretically investigated the band structure of antiperovskite chromium-based carbides and nitrides Cr3PX (X = C and N) using the first-principles calculation based on the FP-APW+LO method. The principal structural properties i.e., lattice constants (a,b,c) and internal parameters are in accordance with the experimental results. The calculated values of elastic constants indicated that the mechanical strength for both Cr3PC and Cr3PN compounds at (001) plane is higher than the (100) and (010) planes. Moreover, the Cr3PX compounds are expected to be hard materials with ductile nature. In addition, we have found that the FM ground state of herein materials Cr3PC and Cr3PN are energetically favorable with low magnetic moments of about 2.27 and 2.94 μB, respectively, confirming that these are weak ferromagnets. Based on the spin-polarized electronic band structure we have found that both alloys have metallic behavior, such behavior has been shown in the calculated electrical conductivity. We have also estimated other thermoelectric constants like the Seebeck coefficient, thermal conductivity, power factor and electrical resistivity of Cr3PC and Cr3PN compounds.
La revue : Chinese Physics B
Domaine : Physics
Mots Clés : Electronic structure, band gap, optoelectronic, FP-LAPW + lo, TB-LMTO
Auteur : T. Seddik, GÖKAY Uğur, R Khenata, Ş Uğur, Fethi Soyalp, G Murtaza, DP Rai, A Bouhemadou, S Bin Omran
Issn : 1674-1056 Eissn : vol : 25, Num : 10, pp : 107801
Date de publication : 2016-08-25
Résume : In the present work, we investigate the structural, optoelectronic and thermoelectric properties of the YLi3X2 (X = Sb, Bi) compounds using the full potential augmented plane wave plus local orbital (FP-APW+lo) method. The exchange–correlation potential is treated with the generalized gradient approximation/local density approximation (GGA/LDA) and with the modified Becke–Johnson potential (TB-mBJ) in order to improve the electronic band structure calculations. In addition, the estimated ground state properties such as the lattice constants, external parameters, and bulk moduli agree well with the available experimental data. Our band structure calculations with GGA and LDA predict that both compounds have semimetallic behaviors. However, the band structure calculations with the GGA/TB-mBJ approximation indicate that the ground state of the YLi3Sb2 compound is semiconducting and has an estimated indirect band gap (Γ–L) of about 0.036 eV while the ground state of YLi3Bi2 compound is semimetallic. Conversely the LDA/TB-mBJ calculations indicate that both compounds exhibit semiconducting characters and have an indirect band gap (Γ–L) of about 0.15 eV and 0.081 eV for YLi3Sb and YLi3Bi2 respectively. Additionally, the optical properties reveal strong responses of the herein materials in the energy range between the IR and extreme UV regions. Thermoelectric properties such as thermal conductivity, electrical conductivity, Seebeck coefficient, and thermo power factors are also calculated.
La revue : Journal of Electronic Materials
Domaine : Physics
Mots Clés : Electronic structure, band gap, optoelectronic, FP-LAPW + lo, TB-LMTO
Auteur : N Baki, RD Eithiraj, H Khachai, R Khenata, G Murtaza, A Bouhemadou, T. Seddik, S Bin-Omran
Issn : 0947-8396 Eissn : vol : 45, Num : 1, pp : 435-443
Date de publication : 2016-01-01
Résume : The structural, elastic, electronic, optical and thermodynamic properties of the sodium polonide Na2Po compound have been studied through the full potential linearized augmented plane wave plus local orbitals (FP-LAPW + lo) and tight-binding linear muffin-tin orbital (TB-LMTO) methods. The exchange–correlation potential was treated within the local density approximation for the TB-LMTO calculations and within the generalized gradient approximation for the FP-LAPW + lo calculations. In addition, Tran and Blaha-modified Becke–Johnson (TB-mBJ) potential and Engel–Vosko generalized gradient approximation were used for the electronic and optical properties. Ground state properties such as the equilibrium lattice constant, bulk modulus and its pressure derivative were calculated and compared with available data. The single-crystal and polycrystalline elastic constants of the considered compound were calculated via the total energy versus strain in the framework of the FP-LAPW + lo approach. The calculated electronic structure reveals that Na2Po is a direct band gap semiconductor. The frequency-dependent ielectric function, refractive index, extinction coefficient, reflectivity oefficient and electron energy loss function spectra are calculated for a wide energy range. The variations of the lattice constant, bulk modulus, heat capacity, volume expansion coefficient and Debye temperature with temperature and pressure were calculated successfully using the FP-LAPW + lo method in combination with the quasi-harmonic Debye model.
La revue : Journal of Magnetism and Magnetic Materials
Domaine : Physics
Mots Clés : AmO2; GGA+U+SO; Phase transition; Electronic band-structure; Optical properties
Auteur : A Bendjedid, T. Seddik, R Khenata, H Baltache, G Murtaza, A Bouhemadou, S Bin Omran, Sikander Azam, Saleem Ayaz Khan
Issn : 0947-8396 Eissn : vol : 396, Num : , pp : 190-197
Date de publication : 2015-12-15
Résume : In this work, we have investigated the structural, phase transition, optoelectronic and magnetic properties of AmO2 using the full potential linearized augmented plane wave plus local orbital (FP-LAPW+lo) method. The exchange-correlation potential was treated with the generalized gradient approximation (GGA). Moreover, the GGA+U approximation (where U denotes the Hubbard Coulomb energy U term) is employed to treat the f electrons properly. The structurally stable AmO2 compound is the Fm3m phase and at a pressure between 40 and 60 GPa underwent a phase transition to the Pnma phase. Our present calculations have considered ferromagnetic and simple antiferromagnetic ground states and the AF state is favored. However, the experimental situation suggests a complex magnetic structure, perhaps involving multipolar ordering. Our band structure calculation with GGA and GGA+U predicted the metallic behavior of AmO2; however, with the spin–orbit coupling (SOC) added to the Coulomb energy U term, semiconducting ground states with antiferromagnetism is correctly predicted. The projected density of states from the energy-band structure indicates that the band gap opening is governed by the partially filled Am “5f” state, and the calculated gap is approximately 1.29 eV. Moreover, the optical properties reveal strong response of AmO2 in the UV region.
La revue : Journal of alloys and compounds
Domaine : Physics
Mots Clés : NaZnAs; FP-LAPW+lo; Phase transition; Electronic band structure; Optical properties
Auteur : A Djied, T. Seddik, O Merabiha, G Murtaza, R Khenata, R Ahmed, S Bin-Omran, Ş Uğur, A Bouhemadou
Issn : 0925-8388 Eissn : vol : 622, Num : , pp : 812-818
Date de publication : 2015-02-15
Résume : In this study, we predict the structural phase transitions as well as opto-electronic properties of the filled-tetrahedral (Nowotny–Juza) NaZnAs compound. Calculations employ the full potential (FP) linearized augmented plane wave (LAPW) plus local orbitals (lo) scheme. The exchange–correlation potential is treated within the generalized gradient approximation of Perdew–Burke and Ernzerhof (GGA-PBE). In addition, Tran and Blaha (TB) modified Becke–Johnson (mBJ) potential is also used to obtain more accurate optoelectronic properties. Geometry optimization is performed to obtain reliable total energies and other structural parameters for each NaZnAs phase. In our study, the sequence of the structural phase transition on compression is Cu2Sb-type → β → α phase. NaZnAs is a direct (Γ–Γ) band gap semiconductor for all the structural phases. However, compared to PBE-GGA, the mBJ approximation reproduces better fundamental band gaps. Moreover, for insight into its potential for photovoltaic applications, different optical parameters are studied.
La revue : Journal of Magnetism and Magnetic Materials
Domaine : Physics
Mots Clés : Half-metallic; Magnetic moment B and structure; FP-LAPW; GGA
Auteur : M El Amine Monir, H Baltache, G Murtaza, R Khenata, Waleed K Ahmed, A Bouhemadou, S Bin Omran, T. Seddik
Issn : 0304-8853 Eissn : vol : 374, Num : , pp : 50-60
Date de publication : 2015-01-15
Résume : Based on first principles spin-polarized density functional theory, the structural, elastic electronic and magnetic properties of Zn1−xVxSe (for x=0.25, 0.50, 0.75) in zinc blende structure have been studied. The investigation was done using the full-potential augmented plane wave method as implemented in WIEN2k code. The exchange-correlation potential was treated with the generalized gradient approximation PBE-GGA for the structural and elastic properties. Moreover, the PBE-GGA+U approximation (where U is the Hubbard correlation terms) is employed to treat the “d” electrons properly. A comparative study between the band structures, electronic structures, total and partial densities of states and local moments calculated within both GGA and GGA+U schemes is presented. The analysis of spin-polarized band structure and density of states shows the half-metallic ferromagnetic character and are also used to determine s(p)-d exchange constants N0α (conduction band ) and N0β (valence band) due to Se(4p)–V(3d) hybridization. It has been clearly evidence that the magnetic moment of V is reduced from its free space change value of 3 µB and the minor atomic magnetic moment on Zn and Se are generated.
La revue : Journal of alloys and compounds
Domaine : Physics
Mots Clés : FP-APW + lo; Electronic properties; Optical properties; Thermodynamic properties
Auteur : G Murtaza, SK Gupta, T. Seddik, R Khenata, ZA Alahmed, R Ahmed, H Khachai, PK Jha, S Bin Omran
Issn : 0925-8388 Eissn : vol : 597, Num : , pp : 36-44
Date de publication : 2014-06-05
Résume : Structural, elastic, optoelectronic and thermodynamic properties of REGa3 (RE = Sc and Lu) compounds have been studied self consistently by employing state of the art full potential (FP) linearized (L) approach of augmented plane wave (APW) plus local orbitals method. Calculations were executed at the level of Perdew–Burke and Ernzerhof (PBE) parameterized generalized gradient approximation (GGA) for exchange correlation functional in addition to modified Becke–Johnson (mBJ) potential. Our obtained results of lattice parameters show reasonable agreement to the previously reported experimental and other theoretical studies. Analysis of the calculated band structure of ScGa3 and LuGa3 compounds demonstrates their metallic character. Moreover, a positive value of calculated Cauchy pressure, in addition to reflecting their ductile nature, endorses their metallic character as well. To understand optical behavior calculations related to the important optical parameters; real and imaginary parts of the dielectric function, reflectivity R(ω), refractive index n(ω) and electron energy-loss function L(ω) have also been performed. In the present work, thermodynamically properties are also investigated by employing lattice vibrations integrated in quasi harmonic Debye model. Obtained results of volume, heat capacity and Debye temperature as a function of temperature for both compounds, at different values of pressure, are found to be consistent. The calculated value of melting temperature for both compounds (ScGa3 and LuGa3) is found to be similar to the experimental data with an underestimation of 5%.
La revue : Computational materials science
Domaine : Physics
Mots Clés : NaZnP; FP-APW + lo; Phase transition; Elastic constants; Electronic properties; Optical properties
Auteur : A Djied, H Khachai, T. Seddik, R Khenata, A Bouhemadou, N Guechi, G Murtaza, S Bin-Omran, ZA Alahmed, M Ameri
Issn : 0927-0256 Eissn : vol : 84, Num : , pp : 396-403
Date de publication : 2014-03-01
Résume : Ab-initio full potential augmented plane wave plus local orbitals method has been used to investigate the structural phase transition, mechanical and optoelectronic properties of the Nowotny–Juza filled-tetrahedral compound NaZnP. The exchange-correlation potential was treated within the generalized gradient approximation of Perdew–Burke and Ernzerhof (GGA-PBE) and the modified Becke–Johnson potential (TB-mBJ) to improve the accuracy of the electronic band structure. Total-energy and geometry optimizations have been carried out for all structural phases of NaZnP. The following sequence of pressure-driven structural transitions has been found: Cu2Sb-type → β-phase → α-phase. The single-crystal elastic constants of NaZnP in the Cu2Sb-type structure have been calculated using total-energy versus strain method and their corresponding elastic moduli of polycrystalline aggregate, including Young’s modulus, shear modulus and Poisson’s ratio, have been derived. From the elastic parameters, it is inferred that this compound is brittle in nature. The elastic anisotropy was studied in detail using three different indexes; especially the 3D direction dependence of the Young’s modulus was visually described. Furthermore, calculated electronic band structure shows that NaZnP in the Cu2Sb-type phase has a direct energy band gap (Γ–Γ). The TB-mBJ approximation yields larger fundamental band gaps compared to those of PBE-GGA. The examined charge density distributions for the Cu2Sb-type structure show a covalent character for Zn–P bond and ionic nature for Na–P bond. Additionally, real and imaginary parts of the dielectric function, reflectivity and energy loss function spectra have been calculated for radiation up to 30.0 eV with an incident radiation polarized parallel to both [1 0 0] and [0 0 1] crystalline directions.
La revue : Journal of alloys and compounds
Domaine : Physics
Mots Clés : FP-APW + lo; GGA, GGA + U; Magnetic properties; Electronic properties; Thermodynamic properties
Auteur : O Merabiha, T. Seddik, R Khenata, G Murtaza, A Bouhemadou, Y Takagiwa, S Bin Omran, D Rached
Issn : 0925-8388 Eissn : vol : 586, Num : , pp : 529-535
Date de publication : 2014-02-05
Résume : Structural, magnetic, electronic and thermodynamic properties of the hexagonal U3ZrSb5 are theoretically investigated by using the full potential linearized augmented plane wave plus local orbital’s (FP-LAPW + lo) method. The exchange–correlation potential was treated with the generalized gradient approximation GGA of Wu and Cohen. Moreover, the GGA + U approximation (where U is the Hubbard correlation terms) is employed to treat the f electrons properly. The calculated structural parameters are in good agreement with the experimental data. The magnetic study reveals that U3ZrSb5 is a ferromagnetic material. Furthermore, we present a comparative study between the band structures, electronic structures, total and partial densities of states and local moments calculated within both GGA and GGA + U schemes. Our band structure calculations show the metallic behavior of this ferromagnetic compound. The thermodynamic properties are predicted through the quasi-harmonic Debye model, in which the lattice vibrations are taken into account. The variation of relative change in volume, heat capacities and the Debye temperature with temperature and pressure are successfully achieved.
La revue : International Journal of Modern Physics B
Domaine : Physics
Mots Clés : Intermetallics; electronic structure; mechanical properties; thermodynamic properties; ab initio calculations
Auteur : M Ould Kada, T. Seddik, Adlane Sayede, R Khenata, A Bouhemadou, E Deligoz, ZA Alahmed, S Bin Omran, D Rached
Issn : 0217-9792 Eissn : vol : 28, Num : 3, pp : 1450006
Date de publication : 2014-01-30
Résume : Structural, electronic, elastic and thermodynamic properties of Rh3X(X = Zr, Nb, Ta) intermetallic compounds are investigated in the framework of density functional theory (DFT). The exchange-correlation (XC) potential is treated with the generalized gradient approximation (GGA) and local density approximation (LDA). The computed ground state properties agree well with the available theoretical and experimental values. The elastic constants are obtained by calculating the total energy versus volume conserving strains using Mehl model. The electronic and bonding properties are discussed from the calculations of band structures (BSs), densities of states and electron charge densities. The volume and bulk modulus at high pressure and temperature are investigated. Additionally, thermodynamic properties such as the heat capacity, thermal expansion and Debye temperature at high pressures and temperatures are also analyzed.
La revue : Canadian Journal of Physics
Domaine : Physics
Mots Clés : FP-LAPWGGA; Structural properties; half-Heusler
Auteur : A Missoum, T. Seddik, G Murtaza, R Khenata, A Bouhemadou, Y Al-Douri, A Abdiche, H Meradji, H Baltache
Issn : Eissn : vol : 92, Num : 10, pp : 1105-1112
Date de publication : 2014-01-29
Résume : To study the structural, electronic, and optical properties of the half-Heusler CoCrZ (Z = Al, Ga), we have performed ab initio calculations using the full-potential with the mixed basis (APW + lo) method within the generalized gradient approximation. The structural properties as well as the band structures, and total and atomic projected densities of states are computed. From electronic band structures we have found that both compounds have a semimetallic nature. We also studied the evolution of electronic structure of CoCrAl under external hydrostatic pressure. It is found that the pseudo gap around the Fermi level increases continuously with increasing pressure, while the electronic density of states at the Fermi level does not change significantly. Furthermore, the optical properties, such as the dielectric function and refractive index were evaluated and discussed under pressure up to 20 GPa, and the electrical conductivity and electron energy loss were calculated for radiation up to 30 eV. The same way, we have studied the magnetic properties of CoCrAl for lattice expansion up to a = 1.1a0 where a transition from the paramagnetic phase to the half-metallic phase is expected.
La revue : Physica B: Condensed Matter
Domaine : Physics
Mots Clés : Yttrium monochalcogenides; FP-LAPWGGA; Structural properties; Elastic constants; Thermodynamic properties
Auteur : T. Seddik, R Khenata, A Bouhemadou, N Guechi, Adlane Sayede, Dinesh Varshney, Y Al-Douri, AH Reshak, S Bin-Omran
Issn : 0921-4526 Eissn : vol : 428, Num : , pp : 78-88
Date de publication : 2013-11-01
Résume : The full potential linearized augmented plane wave method within the framework of density functional theory is employed to investigate the structural, thermodynamic and elastic properties of the yttrium chalcogenides (YX: X=S, Se, and Te) in their low-pressure phase () and high-pressure phase (). The exchange-correlation potential is treated with the generalized gradient approximation of Perdew–Burke–Ernzerhof (GGA-PBE). Temperature dependence of the volume and both adiabatic and isothermal bulk moduli is predicted for a temperature range from for the both phases of the herein considered materials. Furthermore, we have analyzed the thermodynamic properties such as the heat capacities, CV and CP, thermal expansion, α, and Debye temperature, ΘD, under variable pressure and temperature. We have calculated the isothermal elastic constants CijT of the YX monochalcogenides in both NaCl-B1 and CsCl-B2 phases at zero pressure and a temperature range . The results show that rare earth yttrium monochalcogenides are mechanically stable at high temperature. The elastic anisotropy of all studied materials in the two phases has been studied using three different methods.
La revue : Computational materials science
Domaine : Physics
Mots Clés : A. Alkali metal chalcogenides B. FP-L/APW + lo method D. Structural properties D. Elastic constants D. Electronic properties
Auteur : T. Seddik, R Khenata, A Bouhemadou, D Rached, Dinesh Varshney, S Bin-Omran
Issn : 0927-0256 Eissn : vol : 61, Num : , pp : 206-212
Date de publication : 2012-08-01
Résume : The structural, electronic and elastic properties of the tetragonal alkali metal chalcogenides KLiX [X: S, Se and Te] have been investigated using the full-potential (linearized) augmented plane wave plus local orbitals method. The exchange–correlation potential is treated within the generalized gradient approximation of Wu and Cohen. Moreover, the alternative form of GGA proposed by Engel and Vosko is also used for the electronic properties. The calculated structural parameters are in excellent agreement with the experimental data. The elastic constants Cij are predicted using the total energy variation versus strain technique. The polycrystalline elastic moduli, namely; shear modulus, Young’s modulus, Poisson’s ratio, sound velocities and Debye temperature are derived from the obtained single-crystal elastic constants. Brittleness behavior of these compounds is interpreted via the calculated elastic constants Cij. Calculated band structures show that KLiS and KLiSe have an indirect energy band gap, whereas KLiTe has a direct energy band gap. The contribution of alkali metals and chalcogen atoms to the electronic band structure and electronic density of states has been analyzed. This is the first quantitative theoretical prediction of the elastic and electronic properties for these investigated compounds and still awaits experimental confirmations.
La revue : Applied Physics A
Domaine : Physics
Mots Clés : Ab initio calculation; FP-APW + lo; Structural properties; Elastic constants
Auteur : T. Seddik, R Khenata, O Merabiha, A Bouhemadou, S Bin-Omran, D Rached
Issn : 0947-8396 Eissn : vol : 106, Num : 3, pp : 645-653
Date de publication : 2012-03-01
Résume : The elastic, electronic and thermodynamic properties of fluoro-perovskite KZnF3 have been calculated using the full-potential linearized augmented plane wave (FP-LAPW) method. The exchange-correlation potential is treated with the generalized gradient approximation of Perdew-Burke-Ernzerhof (GGA-PBE). Also, we have used the Engel and Vosko GGA formalism (GGA-EV) to improve the electronic band structure calculations. The calculated structural properties are in good agreement with available experimental and theoretical data. The elastic constants C ij are calculated using the total energy variation with strain technique. The shear modulus, Young’s modulus, Poisson’s ratio and the Lamé coefficients for polycrystalline KZnF3 aggregates are estimated in the framework of the Voigt-Reuss-Hill approximations. The ductility behavior of this compound is interpreted via the calculated elastic constants C ij . Electronic and bonding properties are discussed from the calculations of band structure, density of states and electron charge density. The thermodynamic properties are predicted through the quasi-harmonic Debye model, in which the lattice vibrations are taken into account. The variation of bulk modulus, lattice constant, heat capacities and the Debye temperature with pressure and temperature are successfully obtained.
Prediction study of the structural, elastic and high pressure properties of Yttrium chalcogenide
La revue : Computational materials science
Domaine : Physics
Mots Clés : Yttrium chalcogenides, Ab initio calculation; FP-APW + lo; Structural properties; Phase transition; Elastic constants
Auteur : T. Seddik, R Khenata, A Bouhemadou, Ali H Reshak, F Semari, B Amrani
Issn : 0921-4526 Eissn : vol : 49, Num : 2, pp : 394-399
Date de publication : 2010-08-01
Résume : The full-potential linearized augmented plane-wave plus local orbitals method with the generalized gradient approximation for the exchange–correlation potential (FP-APW + lo-GGA) is used to predict the structural, elastic and high pressure properties of YX with X = S, Se and Te. Ground state properties such as lattice constant, bulk modulus and its pressure derivative are obtained. The pressures at which these compounds undergo structural phase transition from NaCl-type to CsCl-type phases are calculated. The elastic constants and their pressure dependence are calculated using the total energy variation with strain technique. The shear modulus, Young’s modulus, Poisson’s ratio and Lamé’s coefficients are estimated in framework of Voigt–Reuss–Hill approximation for polycrystalline YX aggregates. The Debye temperature is estimated from the average sound velocity. To our knowledge this is the first quantitative theoretical prediction of the elastic and high pressure properties for these compounds and still awaits experimental confirmations.
La revue : Physica B: Condensed Matter
Domaine : Physic
Mots Clés : Lutetium chalcogenidesAb initio calculationFP−APW+loStructural propertiesPhase transitionElastic constants
Auteur : T Seddik, F Semari, R Khenata, A Bouhemadou, B Amrani
Issn : 0921-4526 Eissn : vol : 405, Num : 1, pp : 394-399
Date de publication : 2010-01-01
Résume : Using first-principles density functional calculation, the pressure-induced structural phase transformation and mechanical properties of NaCl type (B1) structure in Lutetium chalcogenides (LuX: X=S, Se, Te) were studied by means of the full-potential augmented plane wave plus local orbitals (FP−APW+lo) method. The calculations were performed within the generalized gradient approximation (GGA) for the exchange-correlation potential. The calculated ground-state properties such us lattice constants agree quit well with the experimental findings. We have determined the full set of first-order elastic constants and their pressure dependence, which have not been calculated and measured yet. The Debye temperature is estimated from the average sound velocity. To our knowledge this is the first quantitative theoretical prediction of the structural phase transition and elastic properties for these compounds and still awaits experimental confirmations.
La revue : Computational materials science
Domaine : Physics
Mots Clés : III-P compoundsFP-APW + loElastic moduliPressure effect
Auteur : A Bouhemadou, R Khenata, M Kharoubi, T. Seddik, Ali H Reshak, Y Al-Douri
Issn : 0927-0256 Eissn : vol : 45, Num : 2, pp : 474-479
Date de publication : 2009-04-01
Résume : The effect of high-pressures on the structural and elastic properties of XP zinc-blende compounds, with X = B, Al, Ga and In, has been investigated using the full-potential augmented plane wave plus local orbitals method within density functional theory. The bulk properties, including lattice constant, bulk modulus and its pressure derivative are obtained. The elastic constants and their pressure dependence are calculated using total energy variation with strain technique. We derived the bulk modulus, shear modulus, Young’s modulus and Poisson’s ratio for ideal polycrystalline XP aggregates. We estimated the Debye temperature of XP compounds from the average sound velocity. Our results are in reasonable agreement with the available theoretical and experimental data.
