Journal of Materials, Processes and Environment

Ab-initio Calculation Of Structural Electronic And Thermodynamic Properties Of Zinc-blende Structure: Znte, Mgte And Their Zn1-x Mgxte Ternary Alloys

Auteurs : Tairi Latifa .

Résumé

The First-principles calculations are performed to study the structural, electronic and thermodynamic properties of Zn1-xMgxTe ternary alloys using the full potential-linearized augmented plane wave method (FP-LAPW) within the density functional theory (DFT). In this approach generalized gradient approximation (PBE-GGA) was used for the exchange-correlation potential. The dependence of the lattice constant bulk modulus and band gap on the composition x was analyzed. The lattice constant for Zn1-xMgxTe alloys exhibits a small deviation from the Vegard’s law. A marginal deviation of the bulk modulus from linear concentration dependence LCD was observed for these alloys. The bowing of the fundamental gap versus composition predicted by our calculations is in good agreement with available theoretical data. The microscopic origins of the gap bowing were explained by using the approach of Zunger and co-workers. To achieve the energy eigen values convergence, the plane wave expansion with RMT Kmax equal to 8.0 was used where RMT is the smallest radii of the muffin-tin spheres and Kmax lmax the cut-off for the wave function basis. The RMT values muffin-tin radii were taken to be 2.25, 2.40 and 2.50 a.u for the B.N and as atoms, respectively. The maximum value for the angular momentum quantum, lmax =10 is utilised for the valence wave function expansion inside the atomic spheres, while the charge density was Fourier expanded up to Gmax =12 (Ryd)1/2. A mesh of 72 and 36 special K-points for the binary compounds and the ternary alloys respectively, were taken in the irreducible wedge of the Brillouin zone for the total energy calculation. Other macroscopic properties such as the function of pressure and temperature are presented in this paper and derived using the standard thermodynamic relations. The thermodynamic stability of this alloy was investigated by calculating the excess enthalpy of mixing, Hm as well as the phase diagram by calculating the critical temperatures, heat capacity and the entropy.

Mots clés

Copper halides, FP-LAPW, First principles calculations, Alloys, Thermodynamic stability.