OIL-WATER INTERFACE IN THE WIDOM MODEL - IS IT SMOOTH, ROUGH OR CRUMPLED

The interface in the two-dimensional Ising model with only nearest-nei ghbour ferromagnetic interactions is known to be rough at all temperat ures T > 0. The Widom model for ternary microemulsions is, effectively , a spin-1/2 Ising model with, not only nearest-neighbour ferromagneti c interactions, but also specific farther-neighbour antiferromagnetic interactions. We investigate the effects of these farther-neighbour in teractions in the Widom model on the roughening properties of the inte rface by carrying out Monte Carlo simulations.