structural and thermodynamic properties of alumina

we have investigated the electronic structure and thermodynamic properties of supercell of the
-al2o3 by first-principles calculation in framework of density functional theory (dft) and full potential linearized augmented plane wave (fp-lapw) with generalized gradient approximation (gga) and by quasi-harmonic debye model. our calculated value for direct band gap of α-al2o3 is 7.2 ev which is very close to its experimental measurement. through the quasi-harmonic debye model, in which the phononic effects are considered, we have obtained successfully the thermodynamic parameters including the relative volume and heat capacity over a pressure range 0-70 gpa and a wide temperature range of 0-2000 k.