Question

If $a$ is edge length of a face centred cubic unit cell, then the distance of closest approach of two particles is:

• A. $0.866a$
• B. $1.732a$
• C. $0.707a$
• D. $1.414a$

Answer 1

The correct option is C $0.707a$

Distance of closest approach of two particles in a face centered cubic unit cell is the distance between a corner atom and the atom at the center.
$d=\frac{a\sqrt{2}}{2}=0.707a$