Lattice dynamics of PbTe polymorphs from first principles

The structure, electronic structure, lattice dynamics and thermodynamics of PbTe polymorphs (B1, Pnma and B2 phase) are systematically investigated via first principle calculations. The calculated lattice constants of PbTe polymorphs are in agreement with the experimental ones. The B1 and Pnma phases are semiconductors with band gap 0.866 and 0.331 eV respectively while the B2 phase is metal. The lattice dynamical results regarding the phonon dispersion curves, phonon density of states and thermodynamic properties are reported, which may provide useful data for further investigation of the phonon contribution to the thermoelectric properties. The vibrational modes at the T point are analyzed using group theory as well as the infrared and Raman spectra activities of the optical phonon branches for the studied polymorphs. Thermodynamics such as enthalpy, free energy, the entropy, heat capacity and Debye temperature in a temperature range of 0–300 K are determined. The present calculation results are in good agreement with the experimental results.