A SYSTEMATIC STUDY OF WATER MODELS FOR MOLECULAR SIMULATION - DERIVATION OF WATER MODELS OPTIMIZED FOR USE WITH A REACTION FIELD

We have performed long molecular dynamics simulations of water using f our popular water models, namely simple point charge (SPC), extended s imple point charge (SPC/E), and the three point (TIP3P) and four point (TIP3P) transferable intermolecular potentials. System sizes of 216 a nd 820 molecules were used to study the dependence of properties on th e system size. All systems were simulated at 300 K with and without re action fields and with two different cutoff radii, in order to study t he impact of the cutoff treatment on density, energy, dynamic, and die lectric properties. Furthermore we generated two special-purpose water models based on the SPC and TIP4P models, for use with a reaction fie ld. The atomic charges and the Lennard-Jones C-12 parameter were optim ized to reproduce the correct energy and pressure using the weak coupl ing algorithm for parameters. Indeed, in simulations without parameter coupling of both new models the density and potential energy were fou nd to be close to the experimental values. The other properties of the se models that we called SPC/RF and TIP4P/RF (where RF stands for reac tion field) rue evaluated and discussed. (C) 1998 American Institute o f Physics.