Hard core Yukawa potential

The hard core Yukawa potential has two forms, the attractive Yukawa potential:

$\Phi \left(r\right)=\left\{{\begin{array}{lll}\infty &;&r<\sigma \\-\left({\frac {\epsilon \sigma }{r}}\right)\exp \left[-\kappa \left({\frac {r}{\sigma }}-1\right)\right]&;&r\geq \sigma \end{array}}\right.$

and the repulsive form

$\Phi \left(r\right)=\left\{{\begin{array}{lll}\infty &;&r<\sigma \\\left({\frac {\epsilon \sigma }{r}}\right)\exp \left[-\kappa \left({\frac {r}{\sigma }}-1\right)\right]&;&r\geq \sigma \end{array}}\right.$

where $\Phi \left(r\right)$ is the intermolecular pair potential, $r$ is the distance, $\sigma$ is the hard diameter, $\epsilon$ is the energy well depth ($\epsilon >0$), and $\kappa$ is a parameter that controls the interaction range ($\kappa >0$).

The repulsive form has been used to study charge-stabilised colloid-colloid interactions.

Critical point

The repulsive form of the potential has no critical point.

Triple points

1. Fouad El Azhar, Marc Baus, Jean-Paul Ryckaert and Evert Jan Meijer "Line of triple points for the hard-core Yukawa model: A computer simulation study", Journal of Chemical Physics 112 pp. 5121- (2000)

Phase diagram

Main article: Phase diagram of the Yukawa potential