Modeling the Monte Carlo simulation of associating fluids

We model the Monte Carlo simulation of a simple associating system to understand and quantify the ability of the simulation to provide measurements of the energy and heat capacity. The simulation is examined for its convergence to the equilibrium degree of association, and separately for the precision of its measurements. The molecular model used for the study was proposed by van Roij; it is very simple, and allows the formation of only chain-like association structures while exhibiting only association and no repulsion or dispersion interactions. However, the model captures the essential features that make the simulation of associating systems difficult, and it yields to various types of analysis. Unbiased and biased simulation methods are studied. Modeling is facilitated by coarse-graining the system in terms of the total number of association bonds. A bond-balance kinetic model is used to examine the convergence behavior of the simulation. An unexpected finding is that the strength of association is th...