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1.
Elastic constants and thermodynamic properties of Mg2SixSn1-x from first-principles calculations
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<正>This paper stuides the elastic constants and some thermodynamic properties of Mg2SixSnn-1(x=0,0.25,0.5, 0.75,1) compounds by first-principles total energy calculations using the pseudo-potential plane-waves approach based on density functional theory,within the generalized gradient approximation for the exchange and correlation potential. The elastic constants of Mg2SixSnn-1 were calculated.It shows that,at 273 K,the elastic constants of Mg2Si and Mg2Sn are well consistent with previous experimental data.The isotropy decreases with increasing Sn content.The dependences of the elastic constants,the bulk modulus,the shear modulus and the Debye temperatures of Mg2Si and Mg2Si0.5Sn0.5 on pressure were discussed.Through the quasi-harmonic Debye model,in which phononic effects were considered,the specific heat capacities of Mg2SixSn1-x at constant volume and constant pressure were calculated.The calculated specific heat capacities are well consistent with the previous experimental data. 相似文献
2.
M. Guemou B. BouhafsA. Abdiche R. KhenataY. Al Douri S. Bin Omran 《Physica B: Condensed Matter》2012,407(8):1292-1300
Density functional calculations are performed to study the structural, electronic and optical properties of technologically important BxGa1−xAs ternary alloys. The calculations are based on the total-energy calculations within the full-potential augmented plane-wave (FP-LAPW) method. For exchange-correlation potential, local density approximation (LDA) and the generalized gradient approximation (GGA) have been used. The structural properties, including lattice constants, bulk modulus and their pressure derivatives, are in very good agreement with the available experimental and theoretical data. The electronic band structure, density of states for the binary compounds and their ternary alloys are given. The dielectric function and the refractive index are also calculated using different models. The obtained results compare very well with previous calculations and experimental measurements. 相似文献
3.
M.A. HelalA.K.M.A. Islam 《Physica B: Condensed Matter》2011,406(24):4564-4568
The elastic, electronic, and optical properties of MNNi3 (M=Zn, Sn, and Cu) have been calculated using the plane-wave ultrasoft pseudopotential technique, which is based on the first-principle density functional theory (DFT) with generalized gradient approximation (GGA). The optimized lattice parameters, independent elastic constants (C11, C12, and C44), bulk modulus B, compressibility K, shear modulus G, and Poisson's ratio υ, as well as the band structures, total and atom projected densities of states and finally the optical properties of MNNi3 have been evaluated and discussed. The electronic band structures of the two hypothetical compounds show metallic behavior just like the superconducting ZnNNi3. Using band structures, the origin of features that appear in different optical properties of all the three compounds has been discussed. The large reflectivity of the predicted compounds in the low energy region might be useful in good candidate materials for coating to avoid solar heating. 相似文献
4.
H. Bouafia B. Sahli S. Hiadsi B. Abidri D. Rached B. Amrani 《Physica B: Condensed Matter》2012,407(12):2154-2159
The structural, elastic, electronic, and thermodynamic properties of the cubic NaAlO3-perovskite are calculated using the full potential linearized augmented plane wave with local orbital (FP-LAPW)+lo. The exchange-correlation energy, is treated in generalized gradient approximation (GGA) using the Perdew–Burke–Ernzerhof (PBE) parameterization. The calculated equilibrium parameter is in good agreement with other works. The bulk modulus, elastic constants and their related parameters, such as Young modulus, shear modulus, and Poisson ratio were predicted. The electronic band structure of this compound has been calculated using the Angel-Vosko (EV) generalized gradient approximation (GGA) for the exchange correlation potential. We deduced that NaAlO3-perovskite exhibit a wide-gap which it is an indirect from R to Γ point. The analysis of the density of states (DOS) curves shows ionic and covalent character bond for Al–O and Na–O respectively. 相似文献
5.
Zhenhai Liang Yongbo DingJinqian Jia Caimei FanPeide Han 《Physica B: Condensed Matter》2011,406(11):2266-2269
A theoretical study on Sb-doped SnO2 has been carried out by means of periodic density functional theory (DFT) at generalized gradient approximation (GGA) level. Stability and conductivity analyses were performed based on the formation energy and electronic structures. The results show that Sn0.5Sb0.5O2 solid solution is stable because the formation energy of Sn0.5Sb0.5O2 is −0.06 eV. The calculated energy band structure and density of states showed that the band gap of SnO2 narrowed due to the presence of the Sb impurity energy levels in the bottom of the conduction band, namely there is Sb 5s distribution of electronic states from the Fermi level to the bottom of conduction band after the doping of antimony. The studies provide a theoretical basis to the development and application of Sn1−xSbxO2 solid solution electrode. 相似文献
6.
The structural, elastic constants and anisotropy of RuB2 under pressure are investigated by first-principles calcula-tions based on the plane wave pseudopotential density functional theory method within the local density approximation (LDA) as well as the generalized gradient approximation (GGA) for exchange and correlation. The results accord well with the available experimental and other theoretical data. The elastic constants, elastic anisotropy, and Debye temperature Θ as a function of pressure are presented. It is concluded that RuB2 is brittle in nature at low pressure, whereas it becomes ductile at higher pressures. An analysis for the calculated elastic constant has been made to reveal the mechanical stability of RuB2 up to 100 GPa. 相似文献
7.
Based on the pseudopotential method under the virtual crystal approximation that takes into account the effect of compositional disorder, the electron and heavy-hole effective masses and the dielectric constants in GaxIn1−xAs (0≤x≤1) have been calculated. The results are firstly used in the Wannier equation, which allowed the determination of the exciton reduced mass, binding energy and Bohr radius; then, the polaron properties have been investigated. In this respect, the Fröhlich coupling parameter, Debye temperature and polaron effective mass are calculated and their dependence on the Ga concentration is examined. For InAs and GaAs, our results are generally in reasonable agreement with the known data in the literature, while for compositions x in the range 0-1, our treatment represents the first theoretical predictions. It is found that the exciton and polaron properties for compositions 0<x<1 differ from those of the parent compounds suggesting thus more diverse opportunities to describe most exciton and polaron properties in ternary mixed crystals of interest. 相似文献
8.
We determine the structural, electronic, elastic and optical properties of fluoro-perovskite KZnF3 using the full potential linear augmented plane wave approach (FP-LAPW) based on the density functional theory (DFT). The exchange-correlation potential is treated by the local density approximation (LDA) and the generalized gradient approximation (GGA). The calculated structural parameters are in good agreement with the available data. We have obtained an indirect band gap. The effect of the pressure on the band gaps is investigated. We evaluate the elastic constants (Cij), elastic moduli and the Debye temperature. The imaginary and the real parts of the dielectric function ε(ω) and some optical constants are also calculated. 相似文献
9.
The pseudo-potential plane-wave method using the generalized gradient approximation (GGA) within the framework of the density functional theory is applied to study the structural and thermodynamic properties of Y 3Al5O12. The lattice constants and bulk modulus are calculated. They keep in good agreement with other theoretical data and experimental results. The quasi-harmonic Debye model, in which the phononic effects are considered, is applied to the study of the thermodynamic properties. The temperature effect on the structural parameters, bulk modulus, thermal expansion coefficient, specific heats and Debye temperatures in the whole range from 0 to 20 GPa and temperature range from 0 to 1500 K. 相似文献
10.
Yong-Kai WeiJing-Xin Yu Zhi-Guo LiYan Cheng Guang-Fu Ji 《Physica B: Condensed Matter》2011,406(23):4476-4482
The elastic and thermodynamic properties of CsCl-type structure CaB6 under high pressure are investigated by first-principles calculations based on plane-wave pseudopotential density functional theory method within the generalized gradient approximation (GGA). The calculated lattice parameters of CaB6 under zero pressure and zero temperature are in good agreement with the existing experimental data and other theoretical data. The pressure dependences of the elastic constants, bulk modulus B (GPa), and its pressure derivative B′, shear modulus G, Young's modulus E, elastic Debye temperature ΘB, Zener's anisotropy parameter A, Poisson ratios σ, and Kleinmann parameter ζ are also presented. An analysis for the calculated elastic constants has been made to reveal the mechanical stability of CaB6 up to 100 GPa. The thermodynamic properties of the CsCl-type structure CaB6 are predicted using the quasi-harmonic Debye model. The pressure-volume-temperature (P-V-T) relationship, the variations of the heat capacity CV, Debye temperature ΘD, and the thermal expansion α with pressure P and temperature T, as well as the Grüneisen parameters γ are obtained systematically in the ranges of 0-100 GPa and 0-2000 K. 相似文献
11.
M.A. AliA.K.M.A. Islam 《Physica B: Condensed Matter》2012,407(6):1020-1026
The structural, elastic, electronic and optical (x=0) properties of doped Sn1−xBixO2 and Sn1−xTaxO2 (0≤x≤0.75) are studied using the first-principles pseudopotential plane-wave method within the local density approximation. The independent elastic constants Cij and other elastic parameters of these compounds have been calculated for the first time. The mechanical stability of the compounds with different doping concentrations has also been studied. The electronic band structure and density of states are calculated and the effect of doping on these properties is also analyzed. It is seen that the band gap of the undoped compound narrowed with dopant concentration, which disappeared for x=0.26 for Bi doping and 0.36 for Ta doping. The materials thus become conductive oxides through the change in the electronic properties of the compound for x≤0.75, which may be useful for potential application. The calculated optical properties, e.g. dielectric function, refractive index, absorption spectrum, loss-function, reflectivity and conductivity of the undoped SnO2 in two polarization directions are compared with both previous calculations and measurements. 相似文献
12.
Qi Song Yu-Qing Hou Li-Sha LiZhen-Yi Jiang Bo ZhouXiao-Dong Zhang 《Physica B: Condensed Matter》2012,407(4):565-570
At the generalized gradient approximation (GGA), the elastic constants of the orthorhombic phase of NH3BH3 were calculated with plane-wave pseudo-potential method. Our calculation showed that the orthorhombic phase NH3BH3 is a loose and brittle material, as well as hard to be deformed, also we calculated the elastic anisotropies and the Debye temperatures from the elastic constants. And from the band structure and density of state (DOS), we concluded that NH3BH3 is a wide-gap semiconductor and the band gap is almost 6.0 eV. The bonds between N atoms and H atoms show a strong covalent characteristic, B atoms and H atoms form ironic bonds, and so as to the B-N bonds. Electrons from the B atoms are absorbed by the H atoms around the B atoms, and the H atoms display electronegativity. 相似文献
13.
Abdel Razik Degheidy Abdel Salam ElabsyElkenany Brens Elkenany 《Superlattices and Microstructures》2012
This work is concerned with the dependence of the electronic energy band structures for GaAs1−xPx alloys on temperature and pressure that is based on local empirical pseudo-potential method. The band structures of GaAs1−xPx alloys were calculated in the virtual crystal approximation using the EPM which incorporates compositional disorder as an effective potential. 相似文献
14.
A. Abdiche R. BaghdadR. Khenata R. RianeY. Al-Douri M. GuemouS. Bin-Omran 《Physica B: Condensed Matter》2012,407(3):426-432
The structural and electronic properties of cubic zinc blende BN, BP, AlN and AlP compounds and their BxAl1−xNyP1−y quaternary alloys, have been calculated using the non relativistic full-potential linearized-augmented plane wave FP-LAPW method. The exchange-correlation potential is treated with the local density approximation of Perdew and Wang (LDA-PW) as well as the generalized gradient approximation (GGA) of Perdew-Burke and Ernzerhof (GGA-PBE). The calculated structural properties of BN, BP, AlN and AlP compounds are in good agreement with the available experimental and theoretical data. A nonlinear variation of compositions x and y with the lattice constants, bulk modulus, direct and indirect band gaps is found. The calculated bowing of the fundamental band gaps is in good agreement with the available experimental and theoretical value. To our knowledge this is the first quantitative theoretical investigation on BxAl1−xNyP1−y quaternary alloy and still awaits experimental confirmations. 相似文献
15.
The density functional theory (DFT) calculations of structural, elastic, electronic and optical properties of the cubic antiperovskite AsNMg3 has been reported using the pseudo-potential plane wave method (PP-PW) within the generalized gradient approximation (GGA). The equilibrium lattice, bulk modulus and its pressure derivative have been determined. The elastic constants and their pressure dependence 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 AsNMg3 aggregate. We estimated the Debye temperature of AsNMg3 from the average sound velocity. This is the first quantitative theoretical prediction of the elastic properties of AsNMg3 compound, and it still awaits experimental confirmation. Band structure, density of states and pressure coefficients of energy gaps are also given. The fundamental band gap (Γ-Γ) initially increases up to 4 GPa and then decreases as a function of pressure. Furthermore, the dielectric function, optical reflectivity, refractive index, extinction coefficient, and electron energy loss are calculated for radiation up to 30 eV. The all results are compared with the available theoretical and experimental data. 相似文献
16.
S. Amari S. MéçabihB. Abbar N. BenosmanB. Bouhafs 《Physica B: Condensed Matter》2012,407(17):3639-3645
We have investigated the structural, electronic and magnetic properties of substitutional europium rare earth impurity in cubic CdS and CdSe by employing the ab-initio method. Calculations were performed by using the full potential linearized augmented plane wave plus local orbitals (FP-L/APW+lo) method within the framework of spin-polarized density functional theory (DFT). The electronic exchange-correlation energy is described by generalized gradient approximation GGA and GGA+U (U is the Hubbard correction). The GGA+U method is applied to the rare-earth 4f states. We have calculated the lattice parameters, bulk modulii, the first pressure derivatives of the bulk modulii and the cohesive energies. The calculated densities of states presented in this study identify the metallic behavior of CdEuS and CdEuSe when we use the GGA scheme, whereas when we use the GGA+U, we see that these compounds are half-metallic. 相似文献
17.
The structural parameters with stability upon Si incorporation and elastic, electronic, thermodynamic and optical properties of Ti3Al1−xSixC2 (0≤x≤1) are investigated systematically by the plane wave pseudopotential method based on the density functional theory (DFT). The increase of some elastic parameters with increasing Si-content renders the alloys to possess higher compressive and tensile strength. The Vickers hardness value obtained with the help of Mulliken population analysis increases as x is increased from 0 to 1. The solid solutions considered are all metallic with valence and conduction bands, which have a mainly Ti 3d character, crossing the Fermi level. The temperature and pressure dependences of bulk modulus, normalized volume, specific heats, thermal expansion coefficient, and Debye temperature are all obtained through the quasi-harmonic Debye model with phononic effects for T=0−1000 K and P=0−50 GPa. The obtained results are compared with other results available. Further an analysis of optical functions for two polarization vectors reveals that the reflectivity is high in the visible–ultraviolet region up to ∼10.5 eV region showing promise as a good coating material. 相似文献
18.
Sunil Singh Chouhan Pooja Soni Gitanjali Pagare S.P. Sanyal M. Rajagopalan 《Physica B: Condensed Matter》2011,406(3):339-344
A theoretical study of structural, electronic, elastic, thermal and mechanical properties of nonmagnetic intermetallics YM (M=Cu, Zn and Ag), which crystallize in CsCl-type structure, is performed using first principles density functional theory based on full potential linearized augmented plane wave (FP-LAPW) method. The calculations are carried out within the generalized gradient approximation (GGA) for the exchange correlation potential. The calculated ground state properties such as lattice constants, bulk modulus and elastic constants agree well with the experiment. From energy dispersion curves, it is found that these compounds are metallic in nature. The ductility of these intermetallics is determined by calculating the bulk to shear ratio B/GH. The calculated results indicate that YAg is the most ductile amongst the present YM compounds. The results obtained are compared with the available experimental and theoretical results. The mechanical and thermal properties are predicted from the calculated values of elastic constants. 相似文献
19.
Z.F. Gu J.C. Zhao J.Q. Li Q.Y. Han 《Journal of magnetism and magnetic materials》2009,321(20):3426-3429
The structure and magnetostriction of Tb0.2Pr0.8(Fe0.4Co0.6)1.93−xCx intermetallic compounds were studied by X-ray diffraction and magnetic measurements. Almost a single cubic Laves phase forms in the alloys for x ≤0.20, and a small amount of C can inhibit the formation of the 1:3 phase. The lattice parameter increases when 0≤x≤0.15, while the Tc and the spontaneous magnetization decreases with increasing x. The lattice parameter decreases slowly when 0.15≤x≤0.30, while the Tc decreases evidently with increasing x. The magnetostriction λa (=λ∥-λ⊥) is improved at low magnetic fields at room temperature for the compounds with 0.05≤x≤0.10, indicating that these C-containing compounds are promising magnetostrictive materials. 相似文献
20.
B. Bahloul A. Bentabet L. Amirouche Y. Bouhadda S. Bounab B. Deghfel N. Fenineche 《Journal of Physics and Chemistry of Solids》2014
Structural, electronic and thermodynamic properties of SrTe and BaTe compounds and their ternary mixed crystals BaxSr1−xTe in the rock-salt structure have been studied with density functional theory (DFT), whereas the optical properties have been obtained by using empirical methods such as the modified Moss relation. The exchange-correlation potential was calculated using the generalized gradient approximation (GGA) of Perdew–Burke–Ernzerhof (PBE) and the local density approximation (LDA) of Teter–Pade (TP). In the present work, we used the virtual-crystal approximation (VCA) to study the effect of composition (x). The calculated lattice parameters at equilibrium volume and the bulk modulus for x=0 and x=1 are in good agreement with the literature data. Furthermore, the BaxSr1−xTe alloys are found to be an indirect band gap semiconductor. In addition, we have also predicted the heat capacities (CV), the entropy(S), the internal energy (U) and the Helmholtz free energy (F) of the parent compounds SrTe and BaTe. 相似文献