Self-assembled monolayer formation of pentamers-like molecules onto FCC(111) surfaces: the case of curcuminoids onto Au(111) surface

Abstract

The adsorption of rigid straight electrically polarized pentamers over a FCC(111) surface is studied. The model was inspired by the deposition of 2-thiophene molecules over the Au(111) surface, which was previously characterized by experimental techniques and simulated under the frame of the density functional theory. We now obtain and report the charge distribution of the molecule which allows to propose a deposition model followed by Monte Carlo simulations over an ad-hoc lattice gas model. We show that for a certain value of the chemical potential there exists an isotropic-nematic phase transition which can explain the formation of a self-assembled monolayer like the one observed in the transmission electron microscopy images. An order parameter is defined to characterize the transition which presents a step-like behavior at a critical chemical potential value. The possible nature of the nematic transition in conjunction with an ergodicity breakdown is discussed as future work by means of statistical physics techniques.

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

“…As mentioned, in our previous paper [41] we found that the system described previously experiences an isotropic-nematic phase transition at a determined critical coverage. Figure 2 shows snapshots of the system experiencing this phase transition.…”

“…In a simplified way we propose that these interaction energies conveniently expressed in k B T (k B is the Boltzmann constant) units, are w HH = 1.0, w HC = 0.5w HH = 014133-3 0.5, and w CC = 1.5w HH = 1.5. As explained in our previous paper [41] (see for example Fig. 2 of that paper and the discussion around it), this set of values manages to reproduce very well the interaction energies of two adsorbed 2-thiophene molecules on its most representative relative orientations, as calculated by Flores et al [42] by DFT calculations.…”

“…In this context, we focus in the present paper on a system of 2-thiophene curcuminoid molecules adsorbed on the Au(111) surface. In a recent paper from our group [41], this system was modeled using a lattice-gas of linear pentamers adsorbed onto a triangular lattice. The model includes intermolecular multipolar interactions between neighboring pentamers, and it was able to reproduce the interaction energies of the most representative orientations of the 2-thiophene molecules over the Au surface which were obtained from previous DFT calculations [42].…”

“…For this purpose, extensive MC simulations supplemented by analysis using finite-size scaling (FSS) theory [45][46][47][48][49] have been carried out to study the critical behavior of the system introduced in Ref. [41]: interacting linear pentamers adsorbed on triangular lattices. A nematic phase, characterized by a big domain of parallel pentamers, is separated from the disordered state by a continuous phase transition occurring at a finite critical lattice coverage (or density).…”