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Abstract
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The point charges are distributed over the soft dissipative
particle dynamics (DPD) beads using a Gaussian of tunable width.
Screening the Gaussian smeared charge distributions, with wider
Gaussians of opposite charge, splits the electrostatic interaction into
the real- and the reciprocal-space contributions. This method is
validated against model test systems in the literature. The method has
also been employed to study self-assembly in solutions of sodium
dodecyl sulfate (SDS) in water. The critical micelle concentration
(CMC) and the equilibrium concentration of free surfactants, in
solutions with SDS concentrations varying from CMC to ?20 times
larger than CMC, are in close agreement with experiment. The
microscopic structure of the micelles and the distributions of its
hydrophobic/hydrophilic groups and counterions at the water interface
are in agreement with experiment. The dynamics of monomer exchange between micelles and solution is examined in terms of
the intermittent and continuous correlation functions for the fluctuation of micelle size with time. Two discrete relaxation
processes, whose relaxation times differ by 2 orders of magnitude are found. Using the natural DPD time unit, defined in terms
of thermal velocity, the relaxation times are an order of magnitude shorter than experimental relaxation times for monomer
exchange and establishment of equilibrium between surfactants in the solution and micelles through diffusion of surfactants.
However, experimentally comparable relaxation times are obtained by defining the DPD time scale such that the calculated
diffusion coefficient of water corresponds to its experimental value.
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