The frameworks of sodalite-like structures and of tetrahedrite-like structures1

Abstract

Abstract Crystal structures containing atoms at the mirror planes of I[unk]3m or in related positions of subgroups of I[unk]3m are discussed. The frameworks of these crystal structures are either heterogeneous or they are homogeneous. In the latter case their frameworks are built up from nearly ideal tetrahedra with common vertices around a point configuration of the cubic invariant lattice complex W*. The geometrical properties of such frameworks are discussed in dependence with the position of the framework atoms. Two types of frameworks, W*(4tc ) and [[unk]2 – I(4t)], referring to sodalite-like structures and tetrahedrite-like structures, respectively, are sufficient to describe all these crystal structures with homogeneous frameworks.