MONTE-CARLO SIMULATION OF N-MEMBER ASSOCIATING FLUIDS - APPLICATION TO ANTIGEN-ANTIBODY SYSTEMS

An association biased Monte Carlo (ABMC) method of simulating associat ing systems with two bonding sites on each particle is described. The method includes a strategy for frequently forming two simultaneous bon ds by a single particle during a Monte Carlo move. This strategy is em ployed to obtain adequate configuration statistics at each state point and is particularly important when ring formation is possible. A vari ety of thermodynamic and physicochemical parameters of the associating system were monitored including the compressibility factor, internal potential energy, isothermal compressibility, chain and ring number, a nd shape were monitored. Our analysis indicated that there is a strong dependence of these monitored quantities upon the angle between vecto rs representing the bonding sites on each particle. Also presented are results which suggest the existence of a two phase region, which we b elieve is a gas-liquid coexistence, which is dependent upon density, b onding energy, and the relative angle between the bonding sites. (C) 1 996 American Institute of Physics.