# Virial equation second coefficient derivation

Tags:
1. Feb 18, 2016

### Aniket1

I've been stuck over this integral for around an hour while studying the derivation of the second coefficient of the virial equation:
∫∫dx1d x2 γ(x1,x2) where γ(x1,x2) is 1 when x1 - x2 < constant.
= V∫ dx2 γ(x1,x2) where V is the integral of dx1.
Given: periodic boundary condition: x1 + V = x1
How do you justify this step?

2. Feb 23, 2016