Electronic structures of C60 and C70 adsorbed on the Cu(111) surface and intramolecular STM images

Recent scanning tunneling microscopy (STM) experiments have revealed that C60 and C70 adsorbed on the Cu(111)-(1×1) substrate show specific bias-voltage-dependent images that seem to reflect individual cage structures. In order to understand this experimental observation, band structures and partial charge-density distributions of C60 and C70 are calculated by means of an all-electron mixed-basis approach. In this paper we adopt two-dimensional molecular models without substrates and proper orientational adsorption geometries of fullerenes. By comparing the calculated charge distributions of the lowest-unoccupied-molecular-orbital bands and the highest-occupied- molecular-orbital bands with the STM images, we find that the intramolecular patterns that change with the bias voltage strongly reflect the positions of five-membered and six-membered rings.