if all the atoms along any one body diagonal are removed, remaining atoms are 6 corners, 6 face centers, 6 total tetrahedral voids and 3 total octahedral voids. For one FCC unit cell, there are total 8 tetrahedral voids (2 along each body diagonal at 1/4 from each corners,, all completely inside FCC unit cell so each contribute complete so there will be 2 tetrahedral voids missing .
Posted by
Satyajeet kumar