Entropy-driven phase transition in a system of long rods on a square lattice

Abstract

The isotropic–nematic (I–N) phase transition in a system of long straight rigid rods of lengthk on square lattices is studied by combining Monte Carlo simulations and theoretical analysis.The process is analyzed by comparing the configurational entropy of the system with thatcorresponding to a fully aligned system, whose calculation reduces to the one-dimensional(1D) case. The results obtained (1) allow us to estimate the minimum value ofk which leads to the formation of a nematic phase and provide an interesting interpretationof this critical value; (2) provide numerical evidence for the existence of a second phasetransition (from a nematic to a non-nematic state) occurring at a density close to1 and (3) allow us to test the predictions of the main theoretical models developed to treatthe polymer adsorption problem.