Hartree-Fock study of lithium hydride with the use of a polarizable basis set

Crystalline LiH is studied at a linear combination of atomic orbitals—Hartree-Fock level of approximation with the use of two basis sets: a minimal basis set comprising a single Slater-type orbital per atom (minimal closed-shell model), and an extended set comprising 11 independent s- and p-type atomic orbitals per unit cell (extended-basis-set model). The problem of an adequate treatment of long-range Coulomb interactions (which is of great importance with polarizable ionic systems) has been solved by including a Madelung potential in the Fock operator. Cohesive energy, bulk modulus, band structure, x-ray structure factors, and electron-momentum distribution data are calculated and discussed. The agreement with experiment is in general very good with the extended-basis-set model. The present study confirms the essentially ionic nature of LiH.