Simulation study of the phase behavior of a planar Maier-Saupe nematogenic liquid

Abstract

Using extensive Monte Carlo simulations and a simple approximation in density functional theory, we study the phase behavior of a fluid of nematogenic molecules with centers of mass constrained to lie in a plane but with axes free to rotate in any direction, both with and without an external disorienting field perpendicular to the plane. We find that simulation predicts the existence of an order-disorder phase transition belonging to the Berezinskii-Kosterlitz-Thouless type, along with a low temperature gas-liquid transition. In contrast to the simulation results, density functional theory predicts a first-order orientational phase transition coupled continuously with a first-order gas-liquid transition. The approximate theoretical approach qualitatively reproduces the field dependence of the order-disorder and gas-liquid transitions but is far from quantitative.

Three-dimensional patchy lattice model for empty fluids

“…In order to compute ω 0 (N) in the WLMC procedure an equilibration scheme based on the Wang-Landau strategy 26,27 is carried out, where the values of ω 0 (N) can vary through the first part of the simulation. 19 Once ω 0 (N) is obtained, the equilibrium simulation (fixed ω 0 (N)) is run, and values of the different properties are computed as a function of N. These results can be used to determine phase equilibria, and using appropriate reweighting techniques to locate the critical points.…”

“…By storing histograms of the mean values of the potential energy: U and its square U 2 as a function of the number of particles N we can apply a reweighting scheme to the results to estimate the thermodynamics at temperatures close to that where the multicanonical simulation is carried out. 19 We proceed to calculate the pseudo-critical points (μ…”

“…The basic protocol to compute LVE was as follows: First we used Wang-Landau multicanonical (WLMC) procedures, [19][20][21][22] supplemented with a finite-size scaling analysis 19,[21][22][23] to compute the value of the chemical potential of the transition at some subcritical temperature, T 0 . This temperature is chosen not too close to the critical temperature of the LVE to find a clear separation between the two phases, but not too far to avoid the sampling difficulties that appear at low temperatures.…”

Demixing in binary mixtures of apolar and dipolar hard spheres

“…This kind of procedures has already been successfully applied to the study of the fluid phase behavior of simple fluids [31][32][33][34] and fluid mixtures. 34 A number of advantages make this class of approaches a preferred tool for these problems.…”

Phase diagram of a two-dimensional lattice gas model of a ramp system

“…41,42,49 Here we will just mention the basic ideas underlying the calculation. Simulations are divided in two parts: equilibration and sampling.…”