This is an implementation of the smoothed square-well potential from Leitold and Dellago JCP 141, 134901 (2014) :

\[V(r) = \frac{\varepsilon}{2} \left\{ \exp\left[\frac{-(r-\sigma)}{a}\right] + \tanh\left[\frac{r-\lambda\sigma}{a}\right] - 1 \right\},\]

of which \(a\) dictates the steepness of the slope of the square well, and \({\lambda\sigma}\) determines the width of the step, and \({\sigma}\) is the bond length of the polymer.

To reproduce the potential in the prior reference, use the code below.

pot = espressopp.interaction.SmoothSquareWell(epsilon=1.0,sigma=1.0,cutoff=2.5)
pot.a = 0.002
pot.Lambda = 1.05

The SmoothSquareWell potential supports VerletListInteraction, FixedPairListInteraction and FixedPairListTypesInteraction.

class espressopp.interaction.SmoothSquareWell.SmoothSquareWell

The SmoothSquareWell potential.