Читать книгу Solid State Chemistry and its Applications - Anthony R. West - Страница 50

This structure is related to fluorite, CaF₂ but only 1/4 of the tetrahedral positions are occupied by anions. Cu forms an fcc array; two tetrahedral sites, at 1/4, 1/4, 1/4 and 3/4, 3/4, 3/4, are occupied by O. Consequently, the CN of Cu is twofold linear, rather than 8‐fold for Ca in fluorite and 4‐fold for Zn in sphalerite. Another way to view the structure is as two interpenetrating lattices, fcc Cu and bcc O, giving a structure that, overall, is primitive cubic, a = 4.267 Å. The linear, or ‘dumbell’ coordination of 2 is unusual for a reasonably sized cation but is a common feature in structures of monovalent Cu 3d ¹⁰ and may be rationalised in terms of sp hybridisation giving two Cu sp hybrid orbitals, arranged linearly.