Space-group Representation in Condensed Models of Inorganic Close-packed Structures

Abstract

EARLIER I described some condensed models of inorganic close-packed structures¹. These were based on standard transparent sheets of film, representing layers of the main types of close packing, in which the occupied holes could be marked out. An approximate three-dimensional representation was obtained by placing these sheets at equal distances in an appropriate supporting rack. It became apparent that the conventional symbols for the elements of symmetry of space groups could also be marked out on these sheets, completing the information contained in the models. The top layers of two of these models, olivine and spinel, are represented in Fig. 1a and b. When the layers are placed in the appropriate supporting rack, screw axes, inversion axes, glide planes, etc., can be easily visualized and related to the actual structure.