Phase transition in two-dimensional dipolar fluids at low densities

Monte Carlo computer simulations of a quasi two-dimensional (2D) dipolar fluid at low and intermediate densities indicate that the structure of the fluid is well described by an ideal mixture of self-assembling clusters. A detailed analysis of the topology of the clusters, of their internal energy and of their size (or mass) distributions is used to obtain approximations to their partition functions. Within the scope of these approximations, the results of this work suggest that the 2D dipolar fluid undergoes a phase transition from a dilute phase characterized by a number of disconnected clusters to a condensed phase characterized by a network or spanning (macroscopic) cluster that includes most of the particles in the system.