The number of close neighbours in a body-centred cubic unti cell of monoatomic substance is,

Options

A. 8
B. 6
C. 4
D. 2

Answer

A

Explanation

Atom . A. is touching 4 unit cells in one layer and 4 on top of these so the no. of shared unit cells by a corner atom in a bcc lattice is = 4 + 4 = 8 . Atom X is inside the unit cell so it is shared by only one unit cell.

Atom . A. is touching 5 atoms in its layer ( B, D, E, N and I) and one atom in the layer above it. So, atom . A. has next coordination no. as 6 (nearest next neighbours). Atom X can touch all corner atoms of its unit cell, so the no. of close neighbours is 8 (coordination no.).