Phase diagram of the penetrable-square-well model

¹ National Institute for Theoretical Physics (NITheP) and Institute of Theoretical Physics Stellenbosch 7600, South Africa
² E. Hála Laboratory of Thermodynamics, Institute of Chemical Process Fundamentals of the ASCR and Department of Physical Chemistry, Institute of Chemical Technology - Prague, 166 28 Praha 6, Czech Republic, EU
³ Departamento de Física, Universidad de Extremadura - E-06071 Badajoz, Spain, EU
⁴ Dipartimento di Scienze Molecolari e Nanosistemi, Università Ca' Foscari Venezia - S. Marta DD2137, I-30123 Venezia, Italy, EU

^a rfantoni@ts.infn.it

Received: 12 October 2010
Accepted: 3 January 2011

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.