Orientational phase transitions in systems of adsorbed molecules

The herringbone orientational transition of ${\mathrm{N}}_2$ molecules adsorbed on the graphite (001) surface has been studied by Monte Carlo simulation. Using the recently developed histogram method combined with an analysis of finite-size scaling and the fourth-order energy cumulant, our results strongly suggest a continuous transition in this model, contrary to the results of previous simulation studies and renormalization-group analysis. The critical exponents are determined to be those of the three-state Potts model, in good agreement with recent experimental results on systems that belong to the same universality class.