BOUNDARY EFFECTS ON A SPIN MODEL - MICROEMULSIONS IN A CONFINED GEOMETRY

Widom formulated a lattice model of microemulsions in terms of a spin-1/2 Ising system with nearest-neighbour ferromagnetic interaction and further-neighbour antiferromagnetic interactions. Through Monte Carlo simulation of the Widom model on a simple cubic lattice of size L(x) x L(y) x L(z) we have investigated the surface effects on the structure by imposing physically-motivated boundary conditions. In an interesting range of the interaction parameters we have observed novel structures in the 'narrow-gap geometry', i.e., L(z) << L(x) = L(y), when L(z) is of the order of the order of a few lattice constants.