title: Critical point of electrolyte mixtures.
abstract: The critical behavior of electrolyte mixtures was studied using grand canonical Monte Carlo simulations. Mixtures consist of large multivalent macroions and small monovalent co- and counterions. The system can be viewed as a binary mixture of macroions (with their counterions) and salt (co- and counterion pair). The primitive model description was used, in which the ions are point charges with a hard core and the solvent is treated as a uniform dielectric continuum. The grand canonical simulations are based on insertions and removals of neutral molecules: macroion with its counterions or coions and a counterion. We propose a distance biasing method that enables direct grand canonical simulations up to charge asymmetry of 10:1. We calculated the critical loci that connect the salt-free state, which consists of only macroions and counterions, with the pure salt state using mixed-field finite-size scaling with no pressure mixing. The critical parameters are determined for macroion to counterion charge asymmetries of 2:1, 3:1, and 10:1. Our results suggest that binary electrolyte mixtures are type-I mixtures, where the two components mix continuously.
authors.affiliation: Soft Condensed Matter Group, Debye Institute, Utrecht University, Princetonplein 5, 3584 CC Utrecht, The Netherlands.
authors.forename: Antti-Pekka
authors.initials: AP
authors.lastname: Hynninen
authors.forename: Marjolein
authors.initials: M
authors.lastname: Dijkstra
authors.forename: Athanassios Z
authors.initials: AZ
authors.lastname: Panagiotopoulos