Semiempirical study of electronic and bonding properties of cobalt silicide clusters

The electronic structure of cobalt silicide clusters Co 7 Si 7 and Si 7 Co 7 was studied in comparison to that of Co 19 and Si 17 clusters under the scope of the MINDO/SR method. Clusters Co 7 Si 7 and Si 7 Co 7 represent the environment of a cobalt atom and that of a silicon atom in the cobalt monosilicide bulk, respectively. It is found that the CoSi bond is essentially sp in character with an indirect participation (by electrostatic interaction) of the cobalt d orbitals. Our calculations show a charge transfer from silicon to the d orbitals of cobalt via sp – sp interaction with an internal sp – d hybridization. The theoretical density of states for cobalt silicide clusters are reported and compared with experimental results of surface spectroscopies. © 1992 by John Wiley & Sons, Inc.