Phase Transitions Due to Softness of the Potential Core

Publisher Website
Google Scholar
Abstract
This paper extends a previous demonstration [Hemmer and Stell, Phys. Rev. Letters 24, 1284 (1970)] showing that for a system in which the pair potential has a hard core plus a negative part, softening the hard core can produce a second transition if a first already exists. Detailed analytic and numerical results for one‐dimensional continuum fluids are given, and our discussion of the lattice gas is further developed. In particular interactions that are repulsive over next‐nearest neighbor cells as well as nearest‐neighbor cells are considered, and it is rigorously shown that as many as four first‐order phase transitions can occur for such potentials, even in one dimension. The relevance of our work to certain features found in real systems (e.g. the possible breakdown of the law of rectilinear diameters, and isostructural solid‐solid transitions) is also discussed, as is the novel critical behavior to be expected of certain two‐ and three‐dimensional lattice systems.