Soft-core square well model

The soft-core square well model is given by

$\Phi _{12}\left(r\right)=\left\{{\begin{array}{lcc}4\epsilon \left[\left({\frac {\sigma }{r}}\right)^{n}-\left({\frac {\sigma }{r}}\right)^{n/2}\right]&;&r\leq r_{m}\\-\epsilon &;&r_{m}<r\leq \lambda \sigma \\0&;&r>\lambda \sigma \end{array}}\right.$

where $\Phi _{12}(r)$ is the intermolecular pair potential, $r_{m}=2^{2/n}\sigma$, $\epsilon$ is the well depth, $r$ is the distance between site 1 and site 2, i.e. $r:=|\mathbf {r} _{1}-\mathbf {r} _{2}|$, σ is the hard diameter and λ > 1.

References

1. Mohammad Shokouhi and Gholam Abbas Parsafar "The effect of steepness of soft-core square-well potential model on some fluid properties", Molecular Physics 106 pp. 103-112 (2008)