Ab initio study of the properties of CuAlSe₂: A chalcopyrite compound

Abstract

The ground-state structural, electronic, optical and thermal properties of CuAlSe₂ compound in the body centered tetragonal phase have been studied by employing the full potential linearized augmented plane wave plus local orbitals method based on the density functional theory. For the exchange-correlation effects we have adopted the local density approximation (LDA), generalized gradient approximation (GGA) due to Perdew, Burke and Ernzerhof (PBE) and Engel and Vosko (EV). At the equilibrium unit cell volume, ration of the lattice constants, c/a, has been obtained as 1.99 and the unit cell constant a₀ = 5.51Å which are well comparable with the experimental results. The energy band gap obtained using EVGGA (1.92 eV) is in good agreement in comparison to that using LDA (1.09 eV), GGA (PBE) (1.26 eV) and other earlier available data. Upper portion of the valance band is mainly composed of Cu-d and Se-p states and they are highly hybridized. The optical properties such as dielectric function, refraction, reflection, conductivity, absorption and loss of energy of CuAlSe₂ are presented. The quasi Harmonic Debye model is applied to study the thermal and vibrational effects for the stable BCT CuAlSe₂. Thermal parameters such as Gruneisen parameter, Debye temperature, specific heat etc have been determined as a function of pressure and temperature.