1. The problem statement, all variables and given/known data A gas of neutral atoms is often modelled as an ideal gas, where the gas atoms are considered to be "elastic billiard balls" that only interact by bouncing off each other in a manner that conservers the total kinetic energy. 2. Relevant equations V(r) = 4(Epsilon)[(delta/r)^12 - (delta/r)^6] in dimensionless form U(xi) = 4 [(1/xi)^12 - (1/xi)^6] xi= delta/r, U = V(r)/epsilon 3. The attempt at a solution so i differentiated V(r) to get F(r),since F(r) = - dV(r)/dr.The force at the minimum of the potential is zero and the potential minimum defines the equilibrium position of the system.