Phase Transition in Particle Systems with a Nonnegatively Defined Interaction Potential

We have obtained equations for calculating the parameters of phase transitions in particle systems with a nonnegatively defined interaction potential. The parametrized Gibbs distribution is part of the basis of our derivation. It takes the features of a non-negatively defined interaction potential into account and leads to the corresponding Bogolyubov chain of equations. Using this approach, we obtain a convenient method for finding the free energy of the system. On the basis of this method, we have studied the phase transition in a system of hard spheres and the dependence of the phase-transition temperature on the temperature of argon at high pressures.