Theory of lattice-dynamical properties of solids: Application to Si and Ge

It is demonstrated that the ab initio pseudopotential theory within the local-density-functional formalism provides an accurate theoretical framework for the study of lattice-dynamical properties of solids. With the use of atomic numbers and masses of constituent elements and the crystal structure as the only input information, the calculated phonon frequencies and mode-Gr\"uneisen parameters at Γ and X, the third-order force constant for LTO (Γ), the shear modulus, and the zone-center TA [110] velocity are all in excellent agreement with experiment. Comparison with other microscopic calculations is made.