Question

Identify the crystal.

1. Write the name of the crystal.

2. How many particles are present the unit cell of this crystal?

3. Write the relation connecting edge length and radius of the particle.

Answer 1

1. Face centred cubic crystal.

2. Particles are present the unit cell of this crystal.

• Contribution from 8 corners = 1/8 × 8 = 1 
• Contribution from 6 face centers = 1/2 × 6 = 3 
• The total number of particles = 4

 3. r = \(\frac{\sqrt2a}{4}\) = \(\frac{a}{2\sqrt2}.\)