Explain how many portions of an atom is located at (a) corner (b) body centre (c) face-centred and (d) edge centre of a cubic unit cell.
(a)- In the corner of a cubic unit cell, eight neighbouring unit cells share the same atom. One unit cell, therefore, shares 1/8th of the atom. (b)- Each unit cell in a cubic unit cell has its own atom in the body centre, which is not shared with its neighbour unit cell. Due to its presence in a single unit cell, an atom's contribution to the unit cell is one. (c)- On the face of a cubic unit cell, six neighbouring unit cells share the same atom. One unit cell, therefore, shares 1/2th of the atom. (d)- A cubic unit cell's edge is always shared by four unit cells at a time. Each unit cell will get 1/4th of an atom located at the edge centre.
