Beyond a Hartree-Fock description of crystalline solids: the case of lithium hydride

It is shown that a local MP2 approach can be conveniently adopted as a first step towards the post-Hartree-Fock description of crystalline solids. The relation of a new periodic MP2 code (CRYSCOR) to a classical Hartree-Fock program (CRYSTAL) is outlined. As an illustration, the case of LiH, a prototypical ionic crystal, is treated in some detail by analyzing the effect of the perturbative correction on equilibrium geometry, lattice energy and electron distribution (X-ray structure factors, directional Compton profiles), with reference to experimental data.