X rays and crystal structure . Fig. 46. Iron Pyrites. parallel to (no). The crystals possess, in fact, allthe elements of symmetry possessed by the cube inFig. 46 (b), taking into account the markings on theface of that cube. Fig. 47, p. 150, represents the structure of ironpyrites as assigned to it by our analysis. In Fig. 47all the atoms of a unit cube are projected on one ofthe cube faces. It is at once evident that there isa reason why markings on the corresponding cubeface of the crystal should go up and down, rather than 150 CRYSTAL SYMMETRY AND THE from left to right, or vice versa. The
X rays and crystal structure . Fig. 46. Iron Pyrites. parallel to (no). The crystals possess, in fact, allthe elements of symmetry possessed by the cube inFig. 46 (b), taking into account the markings on theface of that cube. Fig. 47, p. 150, represents the structure of ironpyrites as assigned to it by our analysis. In Fig. 47all the atoms of a unit cube are projected on one ofthe cube faces. It is at once evident that there isa reason why markings on the corresponding cubeface of the crystal should go up and down, rather than 150 CRYSTAL SYMMETRY AND THE from left to right, or vice versa. The sulphur atoms ofthe structure appear in pairs arranged vertically. Thisis only another way of saying that the structure, likethe crystal, has twofold axes where a holohedralcrystal would have fourfold axes. The twofold screwaxes are marked in position in Fig. 47. The dotted lines represent glide planes of sym-metry. Every cube corner (see Fig. 41) is a centre
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Keywords: ., bookcentury1900, bookdecade1910, bookpublisherlondo, bookyear1915
