The electronic properties of hcp beryllium one-, two-, three-, and four-layer films and of a ${\mathrm{BeH}}_2$ monolayer have been reinvestigated by all-electron Hartree-Fock band-structure calculations with improved basis sets. In agreement with local-density-functional calculations, all Be layers are found to be metallic, in contrast with previous Hartree-Fock calculations, which predicted zero-band-gap semiconductors for the one-layer (1L), 2L, and 3L systems. The metallic character is due to the precursor of the Be(0001) 2${\mathit{p}}_{\mathit{z}}$ surface state crossing the Fermi energy. However, this behavior is not observed for the ${\mathrm{BeH}}_2$ layer, which is still found to be insulating, contrary to local-density calculations, which predicted metallic behavior.

• Received 26 December 1990

DOI:https://doi.org/10.1103/PhysRevB.43.9532