F

One of the two most densely packed crystal structures (see Figure F.1) with

coordination number

atomic packing factor

0.74, and the

close-packed planes

{111} and

close-packed directions

〈

〉

. The radius of

tetrahedral void

equals 0.225

R

and that of

octahedral void

is 0.415

R

, where

R

is the

atomic radius.