A mineral having the formula AB2crystallises in the cubic closed-packed lattice with the A-atoms occupying the lattice point. Fraction of the tetrahedral sites occupied by B-atoms is

AB2 crystalises as cubic close packed (ccp)Thus, A2+ is surrounded by eight B-and B- is surrounded by four A2+Thus, coordination number of A2+= 8Coordination number of B- = 4Number of atoms in tetrahedral in small cube of unit cell of atom B = 4Thus, fraction occupied =44=1(100%)