Abstract:

DV-Xa molecular orbital calculations have been performed on a series of metal carbide clusters to examine the effect of the C2 coordination environment on the electronic structures. It was found that the La 5d and C 2p bands are well-separated and the bonding is nearly ionic character in La6C215+ cluster. The covalency becomes more important if the La atoms in La6C15+2 are replaced by Ni to form the La4Ni4C216+cluster where the Ni 3d and C 2p bands are almost completely overlapped, indicating a strong Ni-C covalent interaction. Moreover, in Sc5Ni4C218+ cluster, besides the Ni-C and C-C covalent interactions there exist also the strong metal-metal bonds due to the two-dimensional Ni-Ni network.

Key words: C₂ near-neighbor environment, Metal carbide clusters, Electronic structure, DV-X_a