question_answer 32)

How many lattice points are there in one unit cell of each of the following lattices? (a) Face centred cubic (b) Face centred tetragonal (c) Body centred cubic  

Answer:

(a) In face centred cubic arrangement, Lattice points located at the corners of the cube = 8 Lattice points located at the centre of each face = 6 Total no. of lattice points = 8 + 6 = 14 (b) In face centred tetragonal, the number of lattice points is also the same i.e., 8 + 6 = 14. (In both the cases, particles per unit cell = 8 x 1/8 + 6 x 1/2 = 4) (c) In body centred cubic arrangement, Lattice points located at the corners of the cube = 8 Lattice points located in the centre of the body = 1 Total no. of lattice points = 8 + 1 = 9 The total number of particles per unit cell = 8 x 1/8 + I = 2.