Interionic interactions in simple metals

Second-order pseudopotential theory is combined with the Fermi-Thomas dielectric response to derive an analytic form for a purely repulsive screened Coulomb interaction between ions balanced by a volume-dependent energy which has no direct influence on the detailed structural properties. The interaction is evaluated for the empty-core pseudopotential and used to give direct predictions of the bulk modulus, the Cauchy ratio $\frac{c_{12}}{c_{44}}$, the Poisson ratio, and the Grüneisen constant for the simple metals, which are compared with experimental values. The interaction is also used to obtain phonon spectra and densities of modes for aluminum, and these are compared to experiment. Finally a simple expression for the principal volume-dependent energy is obtained.