Orientational phase transition in monolayers of multipolar straight rigid rods: The case of 2-thiophene molecule adsorption on the Au(111) surface

Monte Carlo simulations and finite-size scaling theory have been carried out to study the critical behavior and universality for the isotropic-nematic (IN) phase transition in a system of straight rigid pentamers adsorbed on a triangular lattice with polarized nonhomogeneous intermolecular interactions. The model was inspired by the deposition of 2-thiophene molecules over the Au(111) surface, which was previously characterized by experimental techniques and density functional theory. A nematic phase, observed experimentally by the formation of a self-assembled monolayer of parallel molecules, is separated from the isotropic state by a continuous transition occurring at a finite density. The precise determination of the critical exponents indicates that the transition belongs to the three-state Potts universality class. The finite-size scaling analysis includes the study of mutability and diversity. These two quantities are derived from information theory and they have not previously been considered as part of the conventional treatment of critical phenomena for the determination of critical exponents. The results obtained here contribute to the understanding of formation processes of self-assembled monolayers, phase transitions, and critical phenomena from novel compression algorithms for studying mutual information in sequences of data.

Automated summary

Monte Carlo simulations and finite-size scaling theory were used to study the critical behavior and universality of the isotropic-nematic phase transition in a system of rigid pentamers adsorbed on a triangular lattice. The model was inspired by the deposition of 2-thiophene molecules on the Au(111) surface. The nematic phase, observed experimentally, is separated from the isotropic state by a continuous transition and belongs to the three-state Potts universality class. The results contribute to the understanding of self-assembled monolayers, phase transitions, and critical phenomena.