Long-range forces in molecular dynamics calculations on water

Abstract The possibility is investigated of speeding up molecular dynamics calculations on aqueous systems by calculating force contributions in two parts. Explicit calculations are made every time step within inner shells containing 4 to 20 molecules, corrections being made at longer time intervals for the more slowly varying contribution outside the inner shell cutoff. Results indicate possible time savings of a factor of 2 to 4 with no significant decrease in accuracy or exacerbation of energy-conservation problems. By using a very small inner shell, the approach to equilibrium can be very significantly speeded up. The technique is particularly suited to probing those properties (e.g., dielectric) which require an accurate assessment of long-range forces.