Micro-emulsions in oil-water-surfactant mixtures: an Ising lattice gas model

An Ising lattice gas model is constructed for oil-water-surfactant mixtures. The phase diagram of this model is obtained by using mean-field theory and Monte Carlo simulations. The paramagnetic phase displays microstructures similar to those found in laboratory micro-emulsions. Also oil-rich, water-rich, and micro-emulsion phases coexist in certain regions and long-lived, metastable phases are common at low temperatures. Low-period, modulated phases are found. The experimental relevance of these phases and the limitations of the authors model are discussed.