Hartree-Fock investigation of the electron momentum distribution in metallic beryllium

The wave function resulting from an accurate Hartree-Fock computation has been used to describe the electron momentum distribution in beryllium metal. Appreciable discrepancies are found with respect to a simple model that amounts to filling with plane waves the first plus second Brillouin zone. In comparing the calculated with the experimental directional Compton profiles, very close agreement is found in particular with a recent set of accurate -ray profiles. The differential Compton profiles are also semiquantitatively reproduced, better on average than with all previous calculations. Concerning the Fourier transforms of the Compton profiles, all the features of the experimental curves are accurately reproduced, in particular the position of the zero passages, which is a powerful test of the adequacy of a theoretical model to account for the metallic nature of the solid. The possible influence of the correlation correction is discussed, and it is shown that such a correction would substantially improve the overall agreement with the experiment.