Atomic size effect on the structures and stability of X7M (X=Al and In;M=Si−,Ge−,N and P) clusters

Based on the density functional theory, geometric and electronic properties of X7M (X=Al and In; M=Si−, Ge−, N and P) clusters are studied. The lowest-energy structures for Al7Si−, Al7Ge− and Al7P are largely different from that of Al7C−. The size effect of impurity atom on the structures and stability has been analyzed. In7C− and In7N are found to have the same geometry as Al7C−, in which the host atoms form a cage with C3vC3v symmetry with impurity atoms locating at the central site. A significantly large HOMO–LUMO gap, low-electron affinity, and high ionization potential are the characters of a magic cluster found for In7N, which may have potential application in cluster-assembled materials.