Global lowest energy structure of the cluster assembled intermetallic crystal CoIn₆Cs

Abstract The low-energy structures of the cluster assembled intermetallic crystal CoIn 6 Cs are determined by using evolutionary algorithm combined with spin polarized density functional theory. While the Co centered Co@In 6 triangular prism and octahedron, which are the low energy isomers of the free cluster, assembled structures are real stable crystal structures, the lowest energy polymorph is a layered network structure formed by the Co@In 8 units with four shared In atoms. The two pairs of the shared In atoms can be saturated by two In atoms, and the building unit can be regarded as Co@In 10 − . The same as the three known types of 11-atom clusters Tr 10 Zn 8− , Tr 10 M 10− , and Tr 11 7− (Tr = Ga, In, Tl; M = Ni, Pd, Pt), this building unit also has 40 valence electrons. Analyses in the electronic structures show that strong interactions occur between the Co 3d orbitals and the superatomic orbitals formed by the In atoms. Crystal orbital Hamilton population (COHP) analyses suggest the Co-In bonds are strong convalent nature.