TITLE:
Thermal Properties and Phonon Dispersion of Bi2Te3 and CsBi4Te6 from First-Principles Calculations
AUTHORS:
Shen Li, Clas Persson
KEYWORDS:
Quasi Harmonic Approximation, Thermal Expansion, Heat Capacity, Phonon Dispersion
JOURNAL NAME:
Journal of Applied Mathematics and Physics,
Vol.3 No.12,
December
4,
2015
ABSTRACT: The narrow-gap semiconductor CsBi4Te6 is a promising material for low temperature thermoelectric applications. Its thermoelectric property is significantly better than the well-explored, high-performance thermoelectric material Bi2Te3 and related alloys. In this work, the thermal expansion and the heat capacity at constant pressure of CsBi4Te6 are determined within the quasiharmonic approximation within the density functional theory. Comparisons are made with available experimental data, as well as with calculated and measured data for Bi2Te3. The phonon band structures and the partial density of states are also investigated, and we find that both CsBi4Te6 and Bi2Te3 exhibit localized phonon states at low frequencies. At high temperatures, the decrease of the volume expansion with temperature indicates the potential of a good thermal conductivity in this temperature region.