513.001 Molecular and Solid State Physics

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Physical
Constants

Periodic System
of Elements

      

Packing density in the hcp structure

Calculate the ratio c/a ratio for the ideal hexagonal close-packed structure. The ratio of c/a is 1.63 for He4, 1.86 for Zn, and 1.58 for Ti. Compare these values to that for the ideal close-packed structure and speculate on the reasons for the deviations from the ideal structure.