The Effect of Simulation Cell Size on the Diffusion Coefficient of an Ionic Surfactant Aggregate

Results of all-atom molecular dynamics simulation have been presented for salt-free aqueous solutions of sodium dodecyl sulfate at its fixed total concentration in a simulation cell containing one to four preliminarily formed quasi-stable ionic aggregates with equal aggregation numbers n = 32. The obtained molecular dynamics trajectories have been used to study the structural and transport properties of the micellar solution. The value of the counterion diffusion coefficient obtained using the Green–Kubo relation has turned out to be somewhat higher than the corresponding value calculated by the Einstein equation. The diffusion coefficients of the aggregates in the systems containing from two to four aggregates have appeared to be higher than the diffusion coefficient of a single aggregate in a cell. The mean force potential obtained for the interaction between the aggregates having aggregation number n = 32 as a function the distance between the aggregate centers of mass has a local minimum in the system containing four such aggregates.