Bonding and Band Structure of ZrS2and ZrSe2

The charge density transfer, the minimum optical transitions and the valence densities of states (VDOS) calculated within the X α theory with the self-consistent symmetrized orthogonalized plane wave (SCSOPW) method (α = 1, 240 OPW/k) are presented for ZrS 2 and ZrSe 2 . A small chalcogen p z -type charge density transfer together with another one in the gap between the layers in the directions from the chalcogen atoms to the Zr atoms are associated with the interlayer bonding. The minimum optical gaps are found to be from Γ 2 - to L 1 + in agreement with Bullett's result. VDOS agree closely with the X-ray photoemission results. The importance of including the three-peaked structure of VDOS in the interpretation of the optical spectra is stressed.