First-Principle Studies Of Electronic Structure And Phonons In Na_xCoO₂ Material

Thermoelectric material can do a direct conversion from heat energy to electrical ergy. Its application mainly include thermal power generation and thermoelectric oling. Such material has long life,high reliability,no noise and no moving parts,vironment-friendly,basically no maintenance and so on advantages. Compared th conventional thermoelectric materials, NaxCoO2 material can work in a gh-temperature oxidation atmosphere long-time and mostly non toxic,no any llution to environment.In this article the calculation of phonon dispersion relations of Na0.6CoO2 is done the framework of the density functional theory. Exchange-correlation effect is ated in the framework of generalized approximation using a functional proposed Perdew-Burke-Ernzerhof. The whole calculation is carried out by the plane wave (?)f consistent field method (pwscf code). The result show that at different Na sition,unlike almost exactly the same elelctronic structure, phonon spectrum and nsity of states are apparently different. we find that there are two parts of phonons th in the different Na atomic positions, and the gap in Na(2) case is quite smaller m in Na(1) case. The optical phonon frequencies at M and K points are indicate singly degenerated characteristic unlike the center of Brillouin zone phonon modes. Finally, the acoustic phonon frequencies are almost linearly decreased with wave vector around theΓpoint.