Question

How many atoms can be assigned to its unit cell if an element forms [1] a bcc cell,and [2] fcc cell?

Answer 1

The atoms are at the corners of the cubic unit cell and there are two atoms each on the four body diagonals. Now this should be realised that the corners are on body diagonals so the diagonally opposite corner atoms satisfy the condition that two atoms are on each diagonal and we need not count the atoms on body diagonals separately.We need to count only the corner atoms.

Only 1/8 of an atom at a corner of a cubic unit cell belongs to the cell, so number of atoms in the cubic cell =1/8 *8 =1

There is 1 atom in the unit cell.