title: From square-well to Janus: improved algorithm for integral equation theory and comparison with thermodynamic perturbation theory within the Kern-Frenkel model.
abstract: Building upon past work on the phase diagram of Janus fluids [F. Sciortino, A. Giacometti, and G. Pastore, Phys. Rev. Lett. 103, 237801 (2009)], we perform a detailed study of integral equation theory of the Kern-Frenkel potential with coverage that is tuned from the isotropic square-well fluid to the Janus limit. An improved algorithm for the reference hypernetted-chain (RHNC) equation for this problem is implemented that significantly extends the range of applicability of RHNC. Results for both structure and thermodynamics are presented and compared with numerical simulations. Unlike previous attempts, this algorithm is shown to be stable down to the Janus limit, thus paving the way for analyzing the frustration mechanism characteristic of the gas-liquid transition in the Janus system. The results are also compared with Barker-Henderson thermodynamic perturbation theory on the same model. We then discuss the pros and cons of both approaches within a unified treatment. On balance, RHNC integral equation theory, even with an isotropic hard-sphere reference system, is found to be a good compromise between accuracy of the results, computational effort, and uniform quality to tackle self-assembly processes in patchy colloids of complex nature. Further improvement in RHNC however clearly requires an anisotropic reference bridge function.
authors.affiliation: Dipartimento di Scienze Molecolari e Nanosistemi, Università Ca' Foscari Venezia, Calle Larga S. Marta DD2137, I-30123 Venezia, Italy.
authors.forename: Achille
authors.initials: A
authors.lastname: Giacometti
authors.affiliation: Max-Planck-Institute for Dynamics and Self-Organization, Göttingen, Germany.
authors.forename: Christoph
authors.initials: C
authors.lastname: Gögelein
authors.affiliation: Department of Physics, North Carolina State University, Raleigh, North Carolina 27695-8202, USA.
authors.forename: Fred
authors.initials: F
authors.lastname: Lado
authors.affiliation: Dipartimento di Fisica and CNR-SOFT, Università di Roma La Sapienza, Piazzale A. Moro 2, 00185 Roma, Italy.
authors.forename: Francesco
authors.initials: F
authors.lastname: Sciortino
authors.affiliation: Institut für Theoretische Physik and Center for Computational Materials Science, Technische Universität Wien, Wiedner Hauptstraße 8-10/136, A-1040 Wien, Austria.
authors.forename: Silvano
authors.initials: S
authors.lastname: Ferrari
authors.affiliation: Dipartimento di Fisica dell' Università di Trieste and CNR-IOM, Strada Costiera 11, 34151 Trieste, Italy.
authors.forename: Giorgio
authors.initials: G
authors.lastname: Pastore