Penetrable-square-well fluids: Analytical study and Monte Carlosimulations

摘要

We study structural and thermophysical properties of a one-dimensional classical fluid made ofpenetrable spheres interacting via an attractive square-well potential. Penetrability of the spheres isenforced by reducing from infinite to finite the repulsive energy barrier in the pair potentials As aconsequence, an exact analytical solution is lacking even in one dimension. Building upon previousexact analytical work in the low-density limit [A. Santos, R. Fantoni, and A. Giacometti, Phys. Rev.E 77, 051206 (2008)], we propose an approximate theory valid at any density and in thelow-penetrable regime. By comparison with specialized Monte Carlo simulations and integralequation theories, we assess the regime of validity of the theory. We investigate the degree ofinconsistency among the various routes to thermodynamics and explore the possibility of afluid-fluid transition. Finally we locate the dependence of the Fisher–Widom line on the degree ofpenetrability. Our results constitute the first systematic study of penetrable spheres with attractionsas a prototype model for soft systems.