Classification of heavy metal fluorides. Fluorides with a body-centered cubic cationic sublattice (Rhombododecahedral complex)

Abstract

The structures of some binary and ternary fluorides with Rb, Cs, K, Na, In, Tr, Te, U, Th, etc., are analyzed, which belong to cubic, tetragonal, orthorhombic, and monoclinic crystal systems and have a cationic sublattice with a more or less deformed cubic I-cell. Six families of planes, most densely populated by cations, are oriented in the sublattice as {110} rhombododecahedral faces. Their intersection points determine cation positions. When the sublattice sites are populated by cations of different types, there is a tendency toward mutual isolation of high-charged cations. The interplanar distances between rhombododecahedral planes relate to those between {200} cubic planes as 1∶0.71, serving to diagnose the presence of an I-subcell. The form of the polyhedron cut out by close-packed cation planes is found to be comparable to the first Brillouin zone.