Characteristic structures of ionic solids
المؤلف:
Peter Atkins, Tina Overton, Jonathan Rourke, Mark Weller, and Fraser Armstrong
المصدر:
Shriver and Atkins Inorganic Chemistry ,5th E
الجزء والصفحة:
ص77-78
2025-08-21
474
Characteristic structures of ionic solids
The ionic structures described in this section are prototypes of a wide range of solids. For instance, although the rock-salt structure takes its name from a mineral form of NaCl, it is characteristic of numerous other solids (Table 3.4). Many of the structures can be regarded as derived from arrays in which the larger of the ions, usually the anions, stack together in ccp or hcp patterns and the smaller counter-ions (usually the cations) occupy the octahedral or tetrahedral holes in the lattice (Table 3.5). Throughout the following discussion, it will be helpful to refer back to Figs 3.18 and 3.20 to see how the structure being described is related to the hole patterns shown there. The close-packed layers usually need to expand to accommodate the counter-ions but this expansion is often a minor perturbation of the anion arrangement, which will still be referred to as ccp and hcp. This expansion avoids some of the strong repulsion between the identically charged ions and also allows larger species to be inserted into the holes between larger ions. Overall, examining the opportunities for hole-filling in a close-packed array of the larger ion type provides an excellent starting point for the descriptions of many simple ionic structures.
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