Isostructural phase transitions due to core collapse. II. A three-dimensional model with a solid–solid critical point

We give a theoretical treatment of isostructural phase transitions that result from partial collapse of the repulsive core of the interparticle pair potential. We use an approximation procedure that is tailored to the high-density regime in which an isostructural solid–solid transition is found for a potential that is the sum of a hard-sphere term and a repulsive shoulder term. A study is made of the transition and its critical point as a function of the potential parameters. We also give an extension of our theory to mixtures, as well as to the shouldered hard-sphere potential to which a long-range attractive tail is added.