Ab initiorelativistic pseudopotential study of the zero-temperature structural properties of SnTe and PbTe

The equilibrium lattice parameters, bulk moduli, cohesive energies, k=0 TO-phonon frequencies and elastic constant $C_{44}$ of SnTe and PbTe are calculated completely from first principles with use of the local-density-functional pseudopotential total-energy method including relativistic effects. Good agreement with experiment is obtained. The approximation of neglecting spin-orbit coupling is found to be adequate for most purposes. Band structures and valence charge densities are presented. The latter are seen to differ significantly from previous empirical-pseudopotential-method calculations. The form of ${\omega }_{\mathrm{TO}\left(\mathrm{P}\right)}$ in PbTe is found to be linear for small pressures P. Some possibilities for further applications of this method to these materials are discussed.