Fomin potential

The Fomin potential is given by (Eq. 2):

$\Phi _{12}\left(r\right)=\left({\frac {d}{r}}\right)^{n}+{\frac {\epsilon }{2}}(1-\tanh(k_{0}(r-\sigma _{s})))$

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, $n=14$ and $k_{0}=10$. $d$ is the diameter of the hard core, $\sigma _{s}$ is the width of the repulsive shoulder, Failed to parse (SVG (MathML can be enabled via browser plugin): Invalid response ("Math extension cannot connect to Restbase.") from server "https://wikimedia.org/api/rest_v1/":): {\displaystyle \epsilon} is the height of the shoulder. As such, this model can be viewed as a softened square shoulder model.