PSEUDOPOTENTIAL PERIODIC HARTREE-FOCK STUDY OF K8IN11 AND RB8IN11 SYSTEMS

The bonding in Ks(8)In(11) and Rb8In11 has been investigated at the SC F level with the periodic Hartree-Fock method. Comparison is made with In-11 clusters with formal charges 7- and 8- calculated at the same l evel. The structure of the 7- cluster has been optimized; it significa ntly differs from the structure observed in the condensed phase. The s econd anion (8-) is found to be dissociative. Moreover, the indium Mul liken populations in dusters are dramatically different from those cal culated for the solid phase. This indicates that the reliability of th e cluster approach is highly questionable. The stability of the solid phases is mostly due to the electrostatic interactions between the ani onic clusters and the alkali counterions. The integrated charge densit y in the cation region is consistent with a picture in which an electr on is delocalized over the potassium layers. The band structure and de nsity of states of the solid phases are discussed. Both K8In11 and Rb8 In11 are found to be weak electronic conductors. At the present state of the art, it is not possible to assess the charge borne by the indiu m cluster and, therefore, to decide whether one or more electrons are delocalized over potassium layers. The bonding in these systems has be en investigated from the topological analysis of the electron localiza tion function point of view. The bonding in the In-11 anionic clusters is characterized by a network of attractors lying 1 Angstrom outward from the indium centers.