THE INVESTIGATION THE STRUCTURAL, ELECTRONIC, ELASTIC, THERMODYNAMICS, AND VIBRATIONAL PROPERTIES SOME OF BINARY (CdS, CdSe, CdTe, CdF2, AlBi, BBi) COMPOUNDS BY AB INITIO METHOD

Bu çalısmada bazı ikili bilesiklerin (CdS, CdSe, CdTe, CdF2, AlBi ve BBi) yapısal, elektronik, elastik, termodinamik ve titresimsel özelikleri normconserving pseudopotansiyel ve yogunluk fonksiyoneli teorisine dayanan ab initio metodla hesaplandı. Bilesiklerin örgü parametreleri, bant yapıları, elastik sabitleri, Debye sıcaklıkları, erime sıcaklıkları, ses hızları, Zener anizotropi faktörü, Young ve Shear modülleri, Poisson oranları, fonon dispersiyon egrileri ve durum yogunlukları hesaplandı. Elde edilen sonuçlar mevcut deneysel ve teorik sonuçlarla karsılastırıldı. Ayrıca, bant aralıgının, elastik ve termodinamik özelliklerin basınçla degisimi incelendi. Kullandıgımız metodun bilesiklerin özelliklerini oldukça dogru bir sekilde tahmin ettigi görüldü. izmir gundem komik videolar cizgi film izle cizgi film 3d oyunlar oyunlar In this work, the structural, electronic, elastic, thermodynamics, and vibrational properties of some binary (CdS, CdSe, CdTe, CdF2, AlBi, and BBi) compounds are calculated by using ab initio calculations within norm-conserving pseudopotentials and density functional theory. For these compounds, the lattice parameters, band structures, elastic constants, Debye temperatures, melting temperatures, sound velocities, Zener anisotropy factors, Poisson ratios, Young and Shear moduli, phonon dispersion curves, and density of state are calculated. The obtained results are compared with the available experimental and theoretical data. Furthermore the pressure-dependence of band gaps, elastic and thermodynamic properties are also investigated. It is found that the method used presented the properties of these compounds quite well

Computational study of mechanical stability and phonon properties of MXenes Mo2ScC2T2(T = O and F): 2D materials

The structural, electronic, elastic, and phonon properties of pristine Mo2ScC2 and surface terminated Mo2ScC2T2 (T = O and F) were investigated by employing density functional theory calculations. Generalized gradient approximation was used to model exchange-correlation effects. The electronic band structure was calculated using both Perdew-Burke-Ernzerhof and Heyd-Scuseria-Ernzerhof functional and found that all considered materials are metallic. Elastic constants, Young's moduli, shear moduli, in-plane stiffnesses, and Poisson's ratios were tabulated and showed that pristine Mo2ScC2 and surface terminated Mo2ScC2T2 satisfy the mechanical stability criteria. Furthermore, Mo2ScC2O2 has been found to be a significant candidate for ultrasensitive sensors due to its ultrahigh Young's modulus. The absence of the imaginary line in phonon band structures confirms the dynamic stability of Mo2ScC2, Mo2ScC2O2, and Mo2ScC2F2. Furthermore, Debye temperatures, phonon group velocities, thermodynamic properties, and Grüneisen parameters were calculated for Mo2ScC2 and Mo2ScC2O2. Finally, it is understood that Mo2ScC2 and Mo2ScC2O2 are suitable candidates for applications that require low thermal conductivity

Mechanical and dynamical stability of TiAsTe compound from ab initio calculations

WOS: 000358148500004The first-principles calculations are employed to provide a fundamental understanding of the structural features and relative thermodynamical, mechanical and phonon stability of TiAsTe compound. The calculated lattice parameters are in good agreement with available experimental results. We have computed elastic constants, its derived moduli and ratios that characterize mechanical properties for the first time. The calculated elastic constants indicate that these materials are mechanically stable at ambient condition. The minimum thermal conductivities of TiAsTe are calculated using both Clarke's model and Cahill's model. Furthermore, the elastic anisotropy has been visualized in detail by plotting the directional dependence of compressibility, Young's modulus and shear modulus. Our results suggest strong elastic anisotropy for this compound. Additionally, the phonon spectra and phonon density of states are also obtained and discussed. The full phonon dispersion calculations confirm the dynamic stability of TiAsTe

The first principles studies of the MgB7 compound: Hard material

WOS: 000319309300013The electronic, mechanical, and vibrational properties of MgB7 are investigated by means of density functional theory as implemented in pseudo-potential plane wave approach. Using the calculated elastic constants, the bulk modulus, shear modulus, Young's modulus, Possion's ratio, Debye temperature, hardness, and anisotropy value were derived. It is found that MgB7 in considered structure is mechanically stable and exhibits brittle character according to the B/G criterion. The band structure of this compound is a semiconductor with an indirect band gap. Furthermore, the phonon dispersion, density of states, Born effective charge tensors, Gruneisen parameter, temperature-dependent variations of the internal energy, free energy, entropy, and heat capacity are also computed and discussed. (C) 2013 Elsevier Ltd. All rights reserved

The structural and mechanical properties of CdN compound: A first principles study

WOS: 000294099900020First principles calculations are performed to investigate the structural, elastic, and mechanical properties of CdN for various structures: NaCl, CsCl, ZnS, wurtzite, WC, CdTe, NiAs, and CuS. The local density and generalized gradient approximations are used for modeling exchange-correlation effects. Our calculations indicate that CuS (B18) structure is energetically the most stable among the considered structures. The some basic physical properties such as lattice parameters, bulk modulus, and second-order elastic constants are calculated. We have also predicted the shear modulus, Young's modulus, Poison's ratio, Debye temperature, and sound velocities. Our structural and some other results are consistent with the available theoretical data

First-principles calculations of vibrational and thermodynamical properties of rare-earth diborides

WOS: 000313561600044We have tried to theoretically predict the lattice dynamical and thermodynamic properties of rare earth diborides (XB2, X = Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm) in AlB2-type structure based on density functional theory within generalized gradient approximation. The calculated equilibrium lattice parameters are in overall agreement with the available experiment and other theoretical results. The phonon dispersion curves are derived by using the direct method. The lattice dynamical results are showed that these compounds are dynamically stable for the considered structure, and these properties exhibits, almost, similar trend for these compounds. In addition, thermodynamic properties such as the free energy, enthalpy, entropy and heat capacity are, also successfully predicted and analyzed with the help of phonon dispersion. (C) 2012 Elsevier B. V. All rights reserved

Phonon transport properties of NbCoSb compound

We present a first-principles study of the phonon transport properties of the Half-Heusler NbCoSb compound. The single crystal elastic constants have been calculated using the stress- strain method. The mechanical properties such as bulk modulus, shear modulus, Young's modulus, Poisson's ratio, and anisotropy factor are estimated using the Voigt-Reuss-Hill approximation. The Grüneisen parameters, phonon life time, and lattice thermal conductivity have been studied in detail. The elastic and phonon properties reveal that this compound is mechanically and dynamically stable. An analysis of the harmonic and anharmonic phonon dispersion and vibrational density of states reveal that, NbCoSb has a very low lattice thermal conductivity, hence, it is a candidate thermoelectric material

Ab initio calculations of the elastic, electronic, optical, and vibrational properties of PdGa compound under pressure

WOS: 000308870300065The structural, elastic, electronic, optical, and vibrational properties of cubic PdGa compound are investigated using the norm-conserving pseudopotentials within the local density approximation (LDA) in the framework of the density functional theory. The calculated lattice constant has been compared with the experimental value and has been found to be in good agreement with experimental data. The obtained electronic band structures show that PdGa compound has no band gap. The second-order elastic constants have been calculated, and the other related quantities such as the Young's modulus, shear modulus, Poisson's ratio, anisotropy factor, sound velocities, and Debye temperature have also been estimated. Our calculated results of elastic constants show that this compound is mechanically stable. Furthermore, the real and imaginary parts of the dielectric function and the optical constants such as the electron energy-loss function, the optical dielectric constant and the effective number of electrons per unit cell are calculated and presented in the study. The phonon dispersion curves are also derived using the direct method

First-principles study of the structural, elastic, electronic, optical, and vibrational properties of intermetallic Pd2Ga

WOS: 000301341400059The structural, elastic, electronic, optical, and vibrational properties of the orthorhombic Pd2Ga compound are investigated using the norm-conserving pseudopotentials within the local density approximation in the frame of density functional theory. The calculated lattice parameters have been compared with the experimental values and found to be in good agreement with these results. The second-order elastic constants and the other relevant quantities, such as the Young's modulus, shear modulus, Poisson's ratio, anisotropy factor, sound velocity, and Debye temperature, have been calculated. It is shown that this compound is mechanically stable after analysing the calculated elastic constants. Furthermore, the real and imaginary parts of the dielectric function and the optical constants, such as the optical dielectric constant and the effective number of electrons per unit cell, are calculated and presented. The phonon dispersion curves are derived using the direct method. The present results demonstrate that this compound is dynamically stable

First-principles study of structural, elastic, electronic and vibrational properties of BiCoO3

WOS: 000340337200001We used density functional theory (DFT) to study the structural, elastic, electronic, and lattice dynamical properties of tetragonal BiCoO3 applying the "norm-conserving" pseudopotentials within the local spin density approximation (LSDA). The calculated equilibrium lattice parameters and atomic displacements are in agreement with the available experimental and theoretical results. Moreover, the structural stability of tetragonal BiCoO3 were confirmed by the calculated elastic constants. In addition, the elastic properties of polycrystalline aggregates including bulk, shear and Young's moduli, and Poisson's ratio are also determined. The electronic band structure, total and partial density of states (DOS and PDOS) with ferromagnetic spin configuration are obtained. The results show that tetragonal BiCoO3 has an indirect band gap with both up- and down-spin configurations and its bonding behavior is of covalent nature. We compute Born effective charge (BEC) which is found to be quite anisotropic of Bi, Co and O atoms. The infrared and Raman active phonon mode frequencies at the Gamma point are found. The phonon dispersion curves exhibit imaginary frequencies which lead from the high-symmetry tetragonal phase to low-symmetry rhombohedral phase in BiCoO3. The six independent elastic constants, including bulk, shear and Young's moduli, and Poisson's ratio, complete BEC tensor and phonon dispersion relations in tetragonal BiCoO3 are predicted for the first time. Results of the calculations are compared with the existing experimental and theoretical data. (C) 2014 Elsevier Masson SAS. All rights reserved.Cukurova University [FEF2011D13, FEF2010BAP8]This work supported by Cukurova University under project number FEF2011D13 and FEF2010BAP8