COMPUTER-SIMULATION OF POLARIZABLE FLUIDS - A CONSISTENT AND FAST WAY FOR DEALING WITH POLARIZABILITY AND HYPERPOLARIZABILITY

The reaction field method has been extended to include polarization effects. This has been the basis for developing a consistent and fast scheme to be used in molecular dynamics simulations for dealing with long-range dipolar forces and many-body polarization effects. The proposed scheme is convenient for large size samples. The computation time is relatively short and increases only proportionally to the number of molecules. The excellent energy conservation is a major advantage and gives confidence for extracting accurate time correlation functions even at long times. As an application we have included the normal polarizability together with the first and second hyperpolarizabilities in a three-point-charge model for water, of the TIP4P type. If we take as standard the CPU time per step (of a vector computer) for the TIP4P water model with a sample of 500 molecules and Ewald sums, the non-polarizable model with reaction field takes from 25 to 50% depending on the cut-off radius and the polarizable model from 50 to 100%.