First-principle study of the lattice dynamic and thermodynamic properties of Zn-based semiconductors with wurtzite structure

The first-principle calculations for the structural, dynamic and thermodynamic properties of the IIB-VIA Zn-based compound semiconductors ZnX (X=O, S, Se, Te) with wurtzite structure are preformed in this work. The density-functional perturbation theory are applied to obtain the Born effective charge tensors, the phonon dispersion curves, as well as corresponding density of states. The results show that the Born effective charge tensors are anisotropic and exhibit the anisotropy of material itself. The calculated phonon frequencies of ZnO and ZnS at Γ point and along high symmetry directions are in agreement with other calculations and experimental data. The phonon contributions to the internal energy, free energy, entropy and specific heat are determined within the harmonic approximation based on the calculated phonon dispersion relations. The calculated results of entropy are slightly larger than the experimental values by about 4.5%, since the effects of anharmonicity are ignored and the theoretical lattice constants are used in the calculations.