Linear response in a density-functional mixed-basis approach

We present a generalization of density-functional based linear-response cal culations of lattice dynamical properties to the case of general energy-ind ependent basis sets. The formalism accounts for the nonorthogonality and at om-position dependence of the basis functions, and is suited for the applic ation of norm-conserving pseudopotentials. We have implemented this scheme in the framework of a mixed-basis pseudopotential technique, which allows a n efficient treatment of localized electrons. The accuracy of the present s cheme is demonstrated by calculations of the phonon dispersions of the 4d m etals Y and Ag [S0163-1829(99)50930-2].