ATOMIC ENVIRONMENT CLASSIFICATION OF THE RHOMBOHEDRAL INTERMETALLIC STRUCTURE TYPES

In this paper we give a complete description of the geometrical atomic environments found in the rhombohedral intermetallic structure types. Our analysis of 195 structure types showed that 144 are possible, whi le the remaining 51 structure types have e.g. improbable interatomic d istances or are excluded because they are oxides with no intermetallic compounds crystallizing in this structure type. In addition, we obser ved that 14 atomic environment types are greatly preferred. Out of 635 6 investigated point sets, 4482 (71%) belong to one of these 14 atomic environment types. Of the 1324 compounds crystallizing in one of the 144 structure types, 19% belong to a single-environment group (structu res in which all atoms have the same type of environment), 15% combine two environment types, 25% have three environments, 34% have four env ironments and the rest (7%) have five or more environments. Our system atic and comprehensive analysis of the rhombohedral structure types ve rified all known relationships between these structure types but also revealed new non-trivial relationships.