Dissipative particle dynamics parametrisation using infinite dilution activity coefficients: the impact of bonding

Dissipative particle dynamics (DPD) simulations have proven to be a valuable coarse-grained simulation technique for studying complex systems such as surfactant and polymer solutions. However, the best method to use in parametrising DPD systems is not universally agreed. One common approach is to map infinite dilution activity coefficients to the DPD simulation 'beads' that represent molecular fragments. However, we show that here that this approach can lead to serious errors when bonding beads together to create molecules. We show errors arise from the verlaps between bonded beads, which alters their solubility. In this article, we demonstrate how these bonding errors can be accounted for when defining DPD force fields using simple theoretical methods to account for the overlapping volumes, and we demonstrate the validity of our approach by calculating the partition coefficients for a series of solutes into two immiscible solvents.