Effective critical point location: application to thiophenes

Abstract

The anisotropic united atom (AUA) 4 model has been used to calculate the vapor–liquid equilibria of thiophene, 2-methylthiophene and 2,5-dimethylthiophene as well as to locate their critical points using Monte Carlo histogram reweighting (HR) techniques combined with either a fourth order cumulant calculation (Binder parameter) or a mixed-field study. The combination of the cumulant method with the use of finite size scaling is found to present advantages with respect to the mixed-field analysis since no matching to the Ising universal distribution is required while maintaining the same statistical efficiency. In particular, the model critical density of thiophene has been located with a statistical accuracy of less than 0.2% within 3% of the experimental value and the model critical temperature has been located with a statistical accuracy of less than 0.1% within 1% of the experimental value.