Lattice Dynamics And Thermodynamics Properties Of Ⅱ-Ⅵ Zn Compound Semiconductors With Wurtzite Structure

II-VI compound semiconductors are being paid to and being widely researched in recent years due to their special optical properties, and their important applications in the laser, infrared and other optical fields. II-VI compound are mainly wide band gaps semiconductors, their band gaps cover the whole visible light spectra, are radiate light almost from the ultraviolet to infrared ragions. At ambient conditions, II-VI Zn-based crystallizes in the wurtzite or sphalerite structure is wide-gap semiconductors with a direct electronic band gap. At present, the research and application of Zn compound semiconductors focus on cubic zinc blend structure, and the research of the hexagonal Zn compound semiconductors with wurtzite still be needed further.In this paper, using the first principles method based on density functional theory, we calculated lattice dynamics and thermodynamic properties of the IIB-VIA Zn-based semiconductor compounds ZnX(X=O, S, Se, Te). Using density-functional perturbation theory, we obtain the Born effective charge tensors of materials, the phonon frequencies at the Brillouin zone center, and the phonon dispersion curves, as well as corresponding density of states and partial density of states. The result of calculation denotes that Born effective charge tensors are anisotropic, exhibit the anisotropy of material itself. By comparison, we found that the calculated phonon frequencies at the Γ point show reasonable agreement with the experimental values and other calculations. The thermodynamics properties including the phonon contribution to the internal energy, the Helmholtz free energy, the entropy, and the constant-volume specific heat of thermodynamic parameters are determined within the quasiharmonic approximation based on the calculated phonon dispersion relations.