The reaction field method in molecular dynamics simulations of point-polarizable water models

Abstract

Models of liquid water have been studied that, while conceptually simple, incorporate the contributions from both molecular polarizability and long-range interactions explicitly. The models use nuclei-centred polarizable point-dipoles in conjunction with the reaction field method, assuming a rigid molecular geometry. In a molecular dynamics implementation of such models, the presence of the reaction field term gives rise to specific additional torques; these are most readily accounted for by a force redistribution method, thus allowing for the use of standard constraint dynamics. It is found that determination of the ‘true’ induced polarization via iteration does not necessarily involve a large computational overhead and hence constitutes a viable alternative to the extended Lagrangian methods that imply internal molecular fluctuations. As an example of this class of water models, the parametrization of simple three- and four-site models with an oxygen-centred isotropic polarizability term has been considered. The results are compared with findings from other recent simulations of polarizable water and illustrate some major trends concerning the effects of the precise specification of the model on structure, energetics and dynamics.