In our paper, we interested in the study of the thermodynamic properties of the compound VSb2. For this, we used the full potential linearized augmented plane wave (FP-LAPW) method implemented in the Wien2k code. The latter is based on the density functional theory (DFT). We also used the Quasi-Harmonic Debye model implemented in the Gibbs2 code. The exchange-correlation energy of electrons was treated using the generalized gradient approximation (GGA) parameterized by Perdew-Burke and Ernzerhof. The calculation of the pressure and the temperature dependence of the thermodynamic properties of VSb2 material is obtained from that of the electronic structure, within the framework of the Quasi-Harmonic Approximation (QHA). We selected a volumes grid enclosing the equilibrium geometry. At these fixed volumes, the rest of the structural parameters are relaxed and we obtain the energy curve as a function of the volume E(V). The thermodynamic properties such as the primitive cell volume V(Bohr3), the bulk modulus B (GPa), the heat capacities CV(J.mol-1.K-1) and CP(J.mol-1.K-1), the thermal expansion coefficient α (K-1), the Grüneisen parameter γ, and the Debye temperature θD(K) have been studied depending on the temperature (T) in the range [0 ; 500 K], and the pressure (P) in the interval [0 ; 15 GPa]. The increase of the bulk modulus is in agreement with the decrease of the volume, also the volume of the primitive cell and bulk modulus are more sensitive to pressure than to temperature. The thermal expansion is more sensitive at low temperatures than at high temperatures. A specific heat behavior of was found, with a Dulong-Petit limit value of 48.16 J.mol-1.K-1. The effect of the pressure on the Grüneisen parameter is opposite to Debye temperature.
This computational study focused on the optical properties of zinc antimonide ZnSb. It relates to the complex dielectric function ε (ω), the refractive index n (ω), the extinction function k (ω), the optical conductivity σ (ω), the reflectivity R(ω), the absorption coefficient α (ω) and the energy loss spectrum L(ω). These properties are calculated and discussed for a growing energy of the incident electromagnetic radiation ranging from 0 to 14 eV, comprising infrared, visible and ultraviolet regions. All these properties are obtained using the Full Potential Linearized Augmented Plane Wave (FP-LAPW), by solving Kohn-Sham equations. This method based on Density Functional Theory (DFT), implemented in Wien2k simulation package. This compound is already used in photo-optical applications, it is for this reason that we interested in the calculation of its optical properties according to the energy of the incident photons, in order to open up for it other use ways. Since the zinc antimonide ZnSb is a semiconductor, its optical properties are investigated using Generalized Gradient Approximation plus modified Becke–Johnson as the exchange correlation (GGA-mBJ). Our calculations are performed by considering only the interband transition of electrons between the occupied states in valence band and unoccupied conduction band states along high symmetry points in Brillouin zone. In addition, the relations of the optical properties to these transitions are discussed in detail. We have also verified the Penn’s model by showing the inverse relationship between the static real part of dielectric function ε1(0) and the optical band gap Eg. The results obtained are compared with other results existing in the literature.
The Electronic and optical properties of zirconium dichalcogenides (ZrS2,ZrSe2, andZrTe2),have been explored via ab-initio methods based on the density functionaltheory (DFT) within the frame of generalized gradient approximation (GGA) and a couplingtechnique between the plane wave (PW) and the pseudo-potential (PP) approaches. Theobtained results showed that ZrS2 and ZrSe2 are semiconducting materials with energy gapsof 1.15 eV and 0.3 eV respectively from the valence band maximum located at G point andthe conduction band minimum located at L point, while ZrTe2 showed a metallic characterwith a density of states at the Fermi level of about 0.8 states/eV. Based on a Kramers–Kroniganalysis of the reflectivity, we have obtained the spectral dependence of the real andimaginary parts of the complex dielectric function (ε1 and ε2, respectively) and the refractiveindex (n). The collected data were used for the calculation of absorption coefficient,reflectivity index, conductivity, and electron energy loss function of ZrS2, ZrSe2, and ZrTe2 forradiation up to 20 eV. All three chalcogenides were found to be good absorbers of ultravioletradiation. The reflectivity of ZrS2 is low in the visible and near-ultraviolet region butincreases sharply for higher photon energies and approaches 96% at ~18.5 eV. The R(ω) spectrum of ZrTe2, on the other hand, is non-selective and remains above 50% over a widerange of energies from infrared to ultraviolet which suggeststhe potential application of thismaterial as an effective solar reflector. On the other hand, the refractive indices of ZrS2, ZrSe2,and ZrTe2 in the visible range are high. The optical spectra show moderate anisotropy concerning the electric field polarization of the incident light.
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