Prism comer-cube

MX planar structure with X groups at the comers of a hexagon MXs a square prism stmcture (cube). 

The compounds KM2F9 with M = Th, U, Np and Pu are all isostmctural, with accurate X-ray data being available for the uranium compound (774). The tricapped trigonal prisms are packed into a complicated three dimensional network sharing edges and comers. The K+ has six fluorines at a distance of 2.7 A and two at 3.09 A to form a distorted cube. 

Box 4 gives an overview over some simple polyhedra with their number of comers, faces and edges that will be taken into account in the following. Except for the deltahedra [R3], [R4], [R5], and [R ] that are defined by equilateral triangles only, two awft-polyhedra with the number of comers and faces inter-changed are included. One of these has only square faces (cube), the other, the trigonal prism, like the also included square pyramid has mixed faces, i.e., triangles and squares. 

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