Theoretical and computational study of a double-Gaussian fluid

Effective interactions in a number of soft matter systems can be described by purely repulsive, bounded potentials, such as the popular Gaussian-core model potential (GCM). In an effort to gain more insight into the general phase behaviour of complex fluids, we investigated a system of point particles whose interaction is modelled by a pair potential combining a bounded short-ranged Gaussian repulsion with a weak longer- ranged Gaussian attraction. The phase diagram of the resulting double-Gaussian model (DGM) shows significant differences when compared with the GCM case: the existence of two fluid phases, a richer solid polymorphism, and a new form of reentrant melting at low density, distinct from the anomalous melting that is observed at higher densities. We have further observed that, in the low pressure/low temperature range, the phase diagram presents some interesting similarities with the phase behaviour of water.