Molecular dynamics (MD) simulation is an attractive tool used to model formulations of surfactant mixtures from first principles, which can be used to predict surfactant morphology and other industrially-relevant thermodynamic properties. However, because of the high sensitivity of surfactant structure to the parameters used in MD simulations, it is often not obvious a priori as to which range of parameter sets should be used. In this work, we compare the performance of a range of ion parameters implemented in non-polarizable classical MD simulations, and its effect on simulations of an idealized solution of sodium dodecyl sulfate (SDS). We find that previous artifacts reported in MD simulations of larger SDS constructs are a direct consequence of using parameters that poorly model ionic interactions at high concentration. Using osmotic pressure and/or other thermodynamic properties measured at finite concentration, such as Kirkwood-Buff integrals, is shown to be the most cost-effective means to validate and parameterize existing force fields. With only the properties of model compounds, we were able to ensure the accuracy of larger SDS constructs (~400 molecules), suggesting that this parameterization strategy is an effective means to validate and develop force fields from first principles. Our findings highlight the importance of optimizing intermolecular parameters for simulations of systems with a high local concentration, which may be applicable in other contexts, such as in molecular crowding, hotspot mapping, protein folding and modeling pH effects.

Accurate parameterization of ionic surfactants at high concentration

249th National Meeting (2015)

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