Gas-liquid phase separation in oppositely charged colloids: Stability and interfacial tension

Abstract

We study the phase behavior and the interfacial tension of the screened Coulomb Yukawarestricted primitive model YRPM of oppositely charged hard spheres with diameter using MonteCarlo simulations. We determine the gas-liquid and gas-solid phase transitions using free energycalculations and grand-canonical Monte Carlo simulations for varying inverse Debye screeninglength . We find that the gas-liquid phase separation is stable for 4, and that the criticaltemperature decreases upon increasing the screening of the interaction decreasing the range of theinteraction. In addition, we determine the gas-liquid interfacial tension using grand-canonicalMonte Carlo simulations. The interfacial tension decreases upon increasing the range of theinteraction. In particular, we find that simple scaling can be used to relate the interfacial tension ofthe YRPM to that of the restricted primitive model, where particles interact with bare Coulombinteractions. © 2006 American Institute of Physics.