What is the packing efficiency achieved by the most efficient sphere packing structures, FCC and HCP?

Answer

Approximately 74%

The Face-Centered Cubic (FCC) and Hexagonal Close-Packed (HCP) structures are the most efficient ways to pack identical spheres, both achieving a packing efficiency close to 74%.

What is the packing efficiency achieved by the most efficient sphere packing structures, FCC and HCP?
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