Effects of the tangentially directed C-σ orbital on the conduction-band electronic structure of the simple-cubic Na2CsC60

The conduction-band electronic structure of the simple-cubic (sc) Na2CsC60 in different molecular orientational states is studied with a tight-binding model in which both the radially directed C-pπ orbital and tangentially directed C-σ orbital are considered. The obtained results are basically in agreement with the previous ones induced by the radially directed C-pπ orbital approximation. This implies that the conduction-band electronic structure of Na2CsC60 is dominated by the radially directed C-pπ orbital. Both the valence and conduction band of the body-centered-cubic (bcc) K6C60 obtained from this tight-binding model are also comparable to the existing ab initio ones.