Electronic structure and optical properties of metallic calcium

Self-consistent Hartree-Fock orbitals of calcium atoms in a crystalline environment were used in conjunction with the localized linear-combination-of-atomic-orbital method to obtain one-electron bands for metallic calcium. Correlation corrections are made by means of Overhauser's simplified method. The metal-to-semimetal-to-metal electronic transitions with increasing pressure are predicted to occur at smaller lattice spacings than predicted by calculations employing local exchange. A rigorous calculation of ${\epsilon }_2$, the imaginary part of complex dielectric function, made within the dipole and one-electron approximation predicts correctly the general shape and width of the $1s$-valence emission spectra and the important structures superimposed on the broad $1s$-conduction absorption spectra. There is good agreement with the specific-heat data, but the details of the Fermi surface as described by de Haas-van Alphen data have remained elusive—large percentage errors occur when the predicted areas are compared with the experimental results. The de Haas-van Alphen orbit areas are extremely sensitive to the accuracy of the calculations due to the flatness of the bands near the Fermi level.