A Kirkwood-Buff Derived Force Field for Thiols, Sulfides, and Disulfides

A force field has been developed for molecular simulations of methanethiol, dimethyl sulfide, and dimethyl disulfide mixtures. The force field specifically attempts to balance the solvation and self-association of these solutes in solution mixtures with methanol. The force field is based on the Kirkwood-Buff (KB) theory of solutions and is parametrized using the KB integrals obtained from the experimental activity, coefficients for the solution mixtures. The transferability of the force field was tested and confirmed by the accurate prediction of the activity coefficients for methanethiol/dimethyl sulfide solutions, which were not used in the initial parametrization of the force fields. The ideality of this latter solution is excellently reproduced. The applicability of the force field to simulations in water was corroborated with a reasonably accurate prediction for the low solubility of dimethyl sulfide in water. The aggregation of methanol molecules at low methanol mole fractions displayed by all the mixtures is reproduced and further analyzed.