The phonon spectra of LiH and LiD from density-functional perturbation theory

We present a self-consistent linear response calculation of phonon dispersion relations in LiH and LiD. Our calculations are performed within density-functional perturbation theory using the local-density approximation and the plane-wave pseudopotential method with the inclusion of the non-linear core correction for exchange and correlation. We accurately estimate zero-point effects on the structural properties at zero temperature. The calculated lattice parameter is a little too small with respect to experiment. The non linear core correction and the inclusion of zero-point effects reduce the discrepancy from 5.1% to 2.5%. Good agreement is obtained between calculated and observed phonon dispersions.