THE CHARACTERIZATION OF COORDINATION POLYHEDRA BY INVARIANTS

We have extended the use of the invariants of spherical harmonics for the characterisation of the angular distribution of coordinating atoms about a central atom. These invariants are suitable indices for use i n clustering algorithms for automatic crystal chemistry. Invariants fo r coordination polyhedra in intermetallic compounds and Ca-O silicates are considered. A study of invariants in coordination polyhedra disto rted by the Jahn-Teller effect is presented. In addition, Invariants f rom small clusters and the cuboctahedron-icosahedron transition are an alyzed.