NaCl crystal structure glide

Figure 9.2 is schematic diagram of the crystal structure of most of the alkali halides, letting the black circles represent the positive metal ions (Li, Na, K, Rb, and Cs), and the gray circles represent the negative halide ions (F, Cl, Br, and I).The ions lie on two interpenetrating face-centered-cubic lattices. Of the 20 alkali halides, 17 have the NaCl crystal structure of Figure 9.1. The other three (CsCl, CsBr, and Csl) have the cesium chloride structure where the ions lie on two interpenetrating body-centered-cubic lattices (Figure 9.3). The plastic deformation on the primary glide planes for the two structures is quite different.

The monoxides are known for all of the rare earth metals. They are all crystallizing at low temperatures isostructural to the NaCl-type. EU3O4 crystallizes orthorhombic [45, 46] with space group Pnam. This mixed valent compound contains Eu + and Eu + in the cation sublattice with a distorted octahedral coordination around Eu + and a coordination number of eight around Eu +. Fig. 3-19 shows the projection of the structure down [010]. The octahedral framework around Eu + can be related by a twinning operation (glide reflection) to the structure of ramsdellite (hep). 

Buerger, M.J. (1930) Translation-gliding in crystals of the NaCl structural type, Am. Mineral. 15, 174 and 226. 

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