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Closest-Packing GLY 4200 Lab 4 – Fall, 2014 1 Hexagonal Closest-Packing (HCP) • Third layer is directly over the first layer • Repeat is ABABAB… 2 Cubic ClosestPacking (CCP) • Third layer is distinct from the first two layers • Repeat is ABCABCABC…. 3 Intralayer Voids • Space between the spheres, within the layer, is a trigonal planar void • A void is a space which may be occupied by a small ion, usually a cation 4 Void:Sphere Ratio • Ratio of voids/spheres • Around each sphere there are six voids • Around each void there are three spheres • The ratio of voids/spheres is therefore 2:1 5 Interlayer Voids • Both types of packing have empty places (voids) between layers • There are two types of voids • Each has a different CN 6 Assignment • Find out what types of voids are present • Find the ratio of voids/sphere for each type • Find the ratio of the voids to one another 7