S. Labidi

Structural, electronic, thermodynamic and optical properties of alkaline earth oxides MgO, SrO and their alloys

The structural, electronic, optical and thermodynamic properties of Mg1 xSrxO ternary alloys in NaCl structures at various Sr concentrations are presented. The calculations were performed using the full potential linearized augmented plane wave (FP-LAPW) method within the density functional theory (DFT) in the local density approximation (LDA) and two developed refinements, namely the generalized gradient approximation (GGA) of Perdew et al (1996 Phys. Rev. Lett. 77 3865) for the structural properties and Engel and Vosko (1993 Phys. Rev. B 47 13164) for the band structure calculations. Deviation of the lattice constants from Vegard’s law and the bulk modulus from the linear concentration dependence (LCD) were observed for the alloys. The microscopic origins of the gap bowing were explained by using the approach of Bernard and Zunger (1986 Phys. Rev. Lett. 34 5982). The refractive index and optical dielectric constant for the alloys of interest were calculated by using different models. In addition, the thermodynamic stability of the alloys was investigated by calculating the critical temperatures of alloys.

FP-LAPW investigations of SrS1−xSex, SrS1−xTex and SrSe1−xTex ternary alloys

The ab initio full potential linearized augmented plane wave (FP-LAPW) method within density functional theory (DFT) was applied to study the effect of composition on the structural, electronic, optical and thermodynamic properties of SrS1−xSex, SrS1−xTex and SrSe1−xTex ternary alloys. For exchange–correlation energy and corresponding potential, the generalized gradient approximation (GGA) by Perdew–Burke–Ernzerhof (PBE) and Engel–Vosko (EVGGA) have been used. Deviation of the lattice constants from Vegards law and the bulk modulus from linear concentration dependence (LCD) were observed for the three alloys. The microscopic origins of the gap bowing were explained by using the approach of Zunger and co-workers. The refractive index and optical dielectric constant for the alloys of interest are calculated by using different models. In addition the thermodynamic stability of the alloys was investigated by calculating the critical temperatures of alloys.

First principle calculations of structural, electronic, thermodynamic and optical properties of Pb1−xCaxS,Pb1−xCaxSe and Pb1−xCaxTe ternary alloys

Using first principles total energy calculations within the full potential linearized augmented plane wave (FP-LAPW) method, we have investigated the structural, electronic, thermodynamic and optical properties of Pb(1-x)Ca(x)S, Pb(1-x)Ca(x)Se and Pb(1-x)Ca(x)Te ternary alloys. The effect of composition on lattice parameter, bulk modulus, band gap, refractive index and dielectric function was investigated. Deviations of the lattice constants from Vegards law and the bulk modulus from linear concentration dependence were observed for the three alloys. Using the approach of Zunger and co-workers, the microscopic origins of band gap bowing have been detailed and explained. The disorder parameter (gap bowing) was found to be mainly caused by the chemical charge transfer effect. On the other hand, the thermodynamic stability of these alloys was investigated by calculating the excess enthalpy of mixing, ΔH(m), as well as the phase diagram. It was shown that all of these alloys are stable at low temperature. The calculated refractive indices and optical dielectric constants were found to vary nonlinearly with Ca composition.

STRUCTURAL, ELECTRONIC, OPTICAL AND THERMODYNAMIC PROPERTIES OF PbS, PbSe AND THEIR TERNARY ALLOY PbS1-xSex

On the basis of ab initio calculations employing density functional theory (DFT), we investigate the structural, electronic, optical and thermodynamic properties of two binaries: PbS and PbSe in rock-salt structures. In addition, several compositions with various ordered structures of PbS1-xSex alloys were studied. The calculations were performed using the full potential linearized augmented plane wave (FP-LAPW) method within the generalized gradient approximation (GGA). Various quantities, such as equilibrium lattice constants, bulk modulus, band structures and refractive index for all Se-concentrations are presented. The microscopic origins of the gap bowing were explained by using the approach of Zunger and coworkers. On the other hand, the thermodynamic stability of these alloys was investigated by calculating the excess enthalpy of mixing ΔHm as well as the phase diagram.

First principles calculations of structural, electronic, thermodynamic and optical properties of BAs1 - xPx alloy

First principles calculations have been used to investigate the structural, electronic, thermodynamic and optical properties of boron ternary alloy BAs1 - x Px, using a hybrid full-potential (linear) augmented plane wave plus the local orbitals (APW + lo) method within the density-functional theory (DFT). The Perdew–Burke–Ernzerhof generalized gradient approximation (PBE-GGA) as well as the Engel–Vosko (EV)-GGA are used to calculate the band gap. We investigated the effect of composition on lattice constant, bulk modulus and band gap. Deviations of the lattice constant from Vegards law and the bulk modulus from linear concentration dependence (LCD) were observed for the alloy. Using the approach of Zunger and co-workers, the microscopic origins of the gap bowing are explained. The thermodynamic stability of the alloy is investigated by calculating the excess enthalpy of mixing ΔHm as well as the phase diagram. The calculated phase diagram showed a broad miscibility gap for the alloy of interest with a high critical temperature. For optical properties, the compositional dependence of the refractive index and the dielectric constant is studied.

Ab initio calculations of fundamental properties of SrTe1−xOx alloys

Structural, electronic, optical and thermodynamic properties of the SrTe1−xOx alloys (0 ≤ x ≤ 1) in rock-salt phase are calculated using the full potential-linearized augmented plane wave (FP-LAPW) method within density functional theory. The exchange-correlation potential for structural properties was calculated by the standard local density approximation (LDA) and GGA (PBE) and the new form of GGA (WC) which is an improved form of the most popular Perdew–Burke–Ernzerhof (PBE), while for electronic properties, in addition to LDA, GGA corrections; Engel–Vosko GGA (EV-GGA) and modified Becke–Johnson (mBJ) schemes were also applied. The results show that the use of GGA (WC) in our calculations is more appropriate than GGA and LDA and gives a good description of structural properties such as lattice parameters and bulk modulus. Our investigation on the effect of composition on lattice constant, bulk modulus and band gap for ternary alloys shows almost nonlinear dependence on the composition. In addition to FP-LAPW method, the composition dependence of the refractive index and the dielectric constant was studied by different models. On the other hand, the thermodynamic stability of this alloy was investigated by calculating the excess enthalpy of mixing ΔHm as well as the phase diagram.