In ABC packing if the number of atoms in the unit cell is n then the number of tetrahedral voids in the unit cell is equal to

No. of effective tetrahedral voids = 2 x no. of effective atoms *large cube is original fcc and smaller cube is an imaginary cube inside the large cube. *These are 8 smaller cube in a bigger cube and each having one void. In fcc there are four atoms so the no. of effective tetrahedral void in a unit cell is double the no. of effective atoms in that unit cell.