Electronic States of C60Molecule on Si(001)2×1 Surface

Electronic states are calculated by the DV-Xα-LCAO method for two model clusters C 60 Si 57 H 44 and C 60 Si 41 H 36 of the C 60 /Si(001) surface, where the C 60 molecule resides on four and two Si dimers, respectively. Due to the electron transfer from the Si surface, the C 60 molecule of the former (latter) cluster has ionicity -2.44 (-1.96). The highest occupied molecular orbital (HOMO) of the C 60 molecule of the former cluster is lower than that of the latter cluster. This implies that the C 60 molecule of the former cluster is more stable than that of the latter cluster. For both clusters, occupied (unoccupied) orbitals of the C 60 molecule near the HOMO have high charge density around double bonds between two hexagons (around single bonds on pentagons). The charge density of an orbital has 4 or more stripes which should be compared with the scanning tunneling microscopy images.