Ab initiocalculations of the dynamic response of beryllium

We present results from ab initio calculations of the full inverse dielectric matrix of beryllium, from which we obtain the dynamic scattering cross section. This is shown to be in excellent agreement with recent inelastic x-ray-scattering experiments, both in overall shape and in precise details of the fine structure. As the calculations have been performed entirely within the random-phase approximation, this presents conclusive evidence that band-structure effects are responsible for the observed structure.