Evidence of sp-mixing effects on thermodynamic and lattice-dynamic properties of Li and Be

It is shown that the generalised non-local model pseudopotential theory, developed recently, can be applied to the calculation of the thermodynamic properties of liquid metallic Li and Be in a fashion similar to its application to the transition metals. The corrections to the effective ionic interaction attributed to one-body plus two-body terms are much less important than those from the three-body plus higher-body terms. In analogy to sd-mixing in the transition metals, the latter are interpreted as arising from sp-mixing effects. These corrections have relatively similar magnitudes in the calculation of the phonon spectra of Li and Be and the latter corrections are required to yield reasonable agreement with observation. Finally, the Be results vindicate the physical interpretation.