Question

Platinum crystallizes in a face – centered cubic crystal with a unit cell of edge length 'a'. The distance between nearest neighbour is:

• A. $a$
• B. $a\frac{\sqrt{3}}{2}$
• C. $a\frac{\sqrt{2}}{2}$
• D. $a\frac{\sqrt{2}}{4}$

Answer 1

The correct option is C $a\frac{\sqrt{2}}{2}$

We are given that Platinum crystallises in FCC lattice. So, in FCC lattice, we have the formula for radius as:

4r = √2a

where a = edge length and r = radius

In FCC lattice, the nearest neighbour atom is calculated by the formula:

2r = √2a / 2