Phase behaviour of heteronuclear dimers adsorbed on square and triangular lattices -: a Monte Carlo study

Monte Carlo simulation within the grand canonical ensemble, the histogram reweighting technique, and finite size scaling analysis are used to explore the phase behaviour of heteronuclear dimers, composed of A and B type segments, on square and triangular lattices. We have considered models with attractive BB and AB nearest-neighbour energy, u(BB) = u(AB) = -1, and the energy u(AA) from the interval [-0.5,0.5]. The phase diagrams and critical parameters have been estimated for both lattices. We have also evaluated the dependences of the critical point characteristics on the value of u(AA). The new ordered structures in liquid phase have been found. It has been shown that for repulsive AA interactions the dimers distributed on a triangular lattice belonged to the two-dimensional Ising class but in the case of a square lattice the system exhibited a non-universal critical behaviour. (C) 2003 Elsevier B.V. All rights reserved.