First-principle calculations of the fundamental properties of CuBrxI1−x ternary alloy

Abstract

Ab initio full-potential linearised augmented plane wave (FP-LAPW) method within density functional theory is applied to study the effect of composition on the structural, electronic and thermodynamic properties of CuBrxI1−x ternary alloy. The structural properties at equilibrium are investigated by using the new form of generalised gradient approximations that are based on the optimisation of total energy. For band structure calculations, both Engel–Vosko and modified Becke–Johnson of the exchange-correlation energy and potential, respectively, are used. Deviation of the lattice constants from Vegard's law and the bulk modulus from linear concentration dependence are observed. The microscopic origins of the gap bowing were explained by using the approach of Zunger and co-workers. On the other hand, 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. A numerical first-principle calculations of the elastic constants as function of pressure is used to calculate C11, C12 and C44.