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

What is the coordination number ( C.N.)of an atom in (i)primitive cubi

1.	What is the coordination number ( C.N.)of an atom in (i)primitive cubic unit cell (ii) body- centred cubic unit cell (iii)face-centredcubic unit cell.
Answer» Solution : (i) In a primitive cubic unit cell, each ATOM has 6 EQUALLY spaced NEAREST nighbours.Hence, C.N. = 6. (ii)In BCC,an atom at the body centre is surrounded by 8 nearest neighbours situted at the corners of the cube. Hence , C.N. = 8 ( REFER to fig 1.12) (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