A unit cell of ccp or fcc lattice is divided into eight small cubes. Then, each small cube has 4 atoms at alternate corners. When these are joined to each other, a regular tetrahedron is formed.
Cnt undrstnd it.. That how tetrahedron is formed on joining them???
tetrahedron is formed by joining four atoms,,..
there are 4 atoms in each small cube,
because in ccp structure there are 4 atoms , they have thus taken atoms alternately .
one tetrahedron makes one tetrahedral void in each small cube , and there are 8 such cubes in the unit cell ,therefore total tetrahedral voids becomes 8.
and as it is CCP lattice there are 4 atoms as whole therefore no. of tetrahedral voids is twice the no. of atoms ..