Question

What is the coordination number (C.N.) of an atom in (i) primitive cubic unit cell (ii) body-centred cubic unit cell (iii)face-centred cubic unit cell .

Answer 1

(i)In a primitive cubic unit cell, each atom has 6 equally spaced nearest neighbours .
(ii)In BCC, an atom at the body centre is surrounded by 8 nearest neighbours situated at the corners of the cube. Hence, C. N. =8.
(iii) In FCC, an atom is surrounded by 12 nearest neighbours (6 in its own plane, 3 above and 3 below). Hence , C.N. =12