REACTIVE CANONICAL MONTE-CARLO - A NEW SIMULATION TECHNIQUE FOR REACTING OR ASSOCIATING FLUIDS

A new simulation technique is developed for calculating the properties of chemically reactive and associating (hydrogen bonding, charge tran sfer) systems. We call this new method reactive canonical Monte Carlo (RCMC). In contrast to previous methods for treating chemical reaction s, this algorithm is applicable to reactions involving a change in mol e number. Stoichiometrically balanced reactions are attempted in the f orward and reverse directions to achieve chemical equilibrium. The tra nsition probabilities do not depend on the chemical potentials or chem ical potential differences of any of the components. We also extend RC MC to work in concert with the isothermal-isobaric ensemble for simula ting chemical reactions at constant pressure, and with the Gibbs ensem ble for simultaneous calculation of phase and chemical equilibria. Ass ociation is treated as a chemical reaction in the RCMC formalism. Resu lts are presented for dimerization of simple model associating fluids. In contrast to previous methods, the reactive Gibbs ensemble can be u sed to calculate phase equilibrium for associating fluids with very st rong bonding sites. RCMC simulations are performed for nitric oxide di merization and results are compared with available experimental data i n the liquid phase. Agreement with experiment is excellent. Results fo r a vapour phase simulation are also in remarkable agreement with esti mates based on second virial coefficient data.