Electronic-structure studies of solids. III. Hartree-Fock band functions and energies for cubic lithium crystals

The authors's methods for Hartree-Fock calculations of electronic structures of solids with exact treatment of exchange are extended to systems containing inner electronic shells and are applied to body-centered-cubic and face-centered-cubic lithium crystals. The calculated structures are found stable relative to ${\mathrm{Li}}_2$ molecules, but the omission of correlation effects and limitations of the basis set preclude a quantitative estimate of the cohesive energy. The variation of total energy with lattice spacing is quite weak, and the calculated equilibrium lattice spacings are about 20% too large. The fcc crystal is calculated to be slightly more stable than the bcc form. From the present results and those of Calais and Sperber, it is concluded that the main deficiency of both wave functions are their inflexible descriptions of lower-symmetry components such as those based on $p$ atomic orbitals.