# Penetrable sphere model

The **penetrable sphere model** is given by ^{[1]}:

where is the intermolecular pair potential, is the hight of the repulsive core, is the distance between site 1 and site 2 and is the radius of the core. Note: an earlier, different, penetrable sphere model was proposed, but is now known as the Widom-Rowlinson model. This model can be seen as the limiting case of the Gaussian overlap model where . In the limit one has the hard sphere model.