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  • Match the type of unit cell given in Column I with the features given in Column II.

Match the type of unit cell given in Column I with the features given in Column II.

Column I Column II
(i) Primitive cubic unit cell

(a) edges of the three perpendicular edges compulsory have different edge lengths, i.e. a\neq b\neq c
(ii) body-centred cubic unit cell (b) Number of atoms per unit cell is one
(iii) Face-centred cubic unit cell

(c) Each of the three perpendicular edges compulsory have the same edge length, i.e. a = b = c
(iv) End-centred orthorhombic unit cell (d) In addition to the contribution from the corner atoms, the number of atoms present in the unit cell is one.
  (e) In addition to the contribution from the corner atoms, the number of atoms present in a unit cell is three.

 

Answers (1)

(i) —>(b, c); (ii) —>(c, d); (iii) —>(c, e); (iv) —> (a, d)
(i) In primitive unit cell, each of the 8 corners contribute 1/8th to the unit cell
Total number of atoms per unit cell = \frac{1}{8}\times 8 = 1

(ii) body-centred cubic unit cell contains atoms at the corners as well as body centre.

Each of the 8 corners contributes 1/8th to the unit cell, and the contribution due to the atom at the centre of the body = 1. 


(iii) In face-centred unit cell, total constituent ions per unit cell present at corners =\frac{1}{8}\times 8 = 1

Total contribution of atoms per unit cell present at face centre =\frac{1}{2}\times 6 = 3

(iv) For end-centred orthorhombic unit cell a\neq b\neq c

each of the 8 corners contribute 1/8th to the unit cell =\frac{1}{8}\times 8 = 1

whereas at end centre, the total contribution is =\frac{1}{2}\times 2 = 1

Thus, other than corner, it contains total one atom per unit cell.

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infoexpert24

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