THE PHONON-SPECTRA OF LIH AND LID FROM DENSITY-FUNCTIONAL PERTURBATION-THEORY

We present a self-consistent linear response calculation of phonon dis persion relations in LiH and LiD. Our calculations are performed withi n density-functional perturbation theory using the local-density appro ximation and the plane-wave pseudopotential method with the inclusion of the non-linear core correction for exchange and correlation. We acc urately estimate zero-point effects on the structural properties at ze ro temperature. The calculated lattice parameter is a little too small with respect to experiment. The non linear core correction and the in clusion of zero-point effects reduce the discrepancy from 5.1% to 2.5% . Good agreement is obtained between calculated and observed phonon di spersions.