Repulsive shoulder system with attractive well potential

The repulsive shoulder system with attractive well potential (RSS-AW) is given by (Eq. 2 ):

${\mathrm{\Phi }}_{12}(r)/ϵ={(\frac{\sigma }{r})}^{14}+{\lambda }_0-{\lambda }_1\tanh (k_1(r-{\sigma }_1))+{\lambda }_2\tanh (k_2(r-{\sigma }_2))$

where

• $r:=|{\mathbf{r}}_1-{\mathbf{r}}_2|$
• ${\mathrm{\Phi }}_{12}(r)$ is the intermolecular pair potential between two particles or sites
• $ϵ$ is the well depth (energy)