C_2近邻环境对金属碳化物电子结构的影响(英文)

Effect of the C_2 Near-neighbor Environment on the Electronic Structures of Metal Carbides

对一系列金属碳化物簇进行了DV－Xa分子轨道计算，探讨了C2配位环境对电子结构的影响.计算结果表明，在La6C15+2簇中，La的5d和C的2p带分开，键基本上是离子性.当La原子被Ni取代形成La4Ni4C16+2簇之后，Ni的3d和C的2p带几乎完全重叠，表明了强的Ni－C共价作用．此外．在Sc5Ni4C18+2簇中，除Ni－C和C－C共价作用外，还存在着强的金属-金属键．

DV-Xa molecular orbital calculations have been performed on a series ofmetal carbide clusters to examinc the cffect of the C2 coordination environment on theelectronic structures. It was follnd that thc La 5d and C 2p bands are well-separatedand the bonding is nearly ionic character in La6C15+2 cluster. The covalency becomesmore important if the La atoms in La,C15+2 are replaced by Ni to form the La4Ni4C16+2cluster where the Ni 3d and C 2p bands are almost completely overlapped, indicatinga strong Ni-C covalent interaction. Moreover, in Sc5Ni4C18+2 cluster, besides the Ni-Cand C-C covalent interactions there exist also the strong metal-metal bonds due to thetwo-dimensional Ni-Ni network.