Sutherland potential

The Sutherland potential ^[1] is given by

\Phi _{12}\left(r\right)=\left\{{\begin{array}{lll}\infty &;&r\leq \sigma \\-\epsilon \left({\frac {\sigma }{r}}\right)^{\gamma }&;&r>\sigma \end{array}}\right.

where $\Phi _{12}\left(r\right)$ is the intermolecular pair potential, $r:=|\mathbf {r} _{1}-\mathbf {r} _{2}|$ is the distance between site 1 and site 2, $\sigma$ is the hard diameter, $\epsilon$ is the energy well depth ( $\epsilon >0$ ), and $\gamma$ is a parameter that controls the interaction range.