Generalized Widom model of amphiphilic systems

An additional two-particle interaction is introduced in the Widom model of microemulsions in order to produce three-phase coexistence between the oil-rich, water-rich, and disordered fluid phases in accordance with experimental results. We test the resulting model numerically through Monte Carlo simulations. We observe a hysteresis in the order parameter and a jump in the surface tension at the transition between the disordered fluid and water-rich and oil-rich phases, thus signifying a first-order transition with three-phase coexistence.