Hi people,

I'm researching about the interactions of two carbon atoms using the Lennard-Jones potential and I need to know the theory behind some equations.

I need to know how to get from the 6-12 potential the 3-9 one. I've found in this link ( 9-3 Lennard-Jones potential page on SklogWiki - a wiki for statistical mechanics and thermodynamics ) a brilliant deduction of what I want applying triple integrals. I understand everything except the limits of the integral respect to z.

From -x to -∞? Why's that?

If someone could throw some light to this issue I would be really grateful.

Thank you in advanced.

Kind regards!