Phase diagram of the penetrable square well-model

TL;DR

This study investigates the phase behavior of penetrable square well colloidal particles using Monte Carlo simulations, revealing stable, unstable, and complex intermediate phases depending on penetrability.

Contribution

It introduces a detailed phase diagram for penetrable square well models, highlighting stability thresholds and complex phase behavior not previously characterized.

Findings

Stable Ruelle systems at low penetrability

Thermodynamic instability and collapse at high penetrability

Rich phase diagram with intermediate behaviors

Abstract

We study a system formed by soft colloidal spheres attracting each other via a square-well potential, using extensive Monte Carlo simulations of various nature. The softness is implemented through a reduction of the infinite part of the repulsive potential to a finite one. For sufficiently low values of the penetrability parameter we find the system to be Ruelle stable with square-well like behavior. For high values of the penetrability the system is thermodynamically unstable and collapses into an isolated blob formed by a few clusters each containing many overlapping particles. For intermediate values of the penetrability the system has a rich phase diagram with a partial lack of thermodynamic consistency.