OBSERVATIONS CONCERNING THE TREATMENT OF LONG-RANGE INTERACTIONS IN MOLECULAR-DYNAMICS SIMULATIONS

Molecular dynamics simulations of pure water employing two different empirical water models have been used to study the effects of different methods for truncation of long-range interactions in molecular mechanics calculations. As has been observed previously in integral equation studies, ''shifting'' these interactions on an atom-by-atom basis was found to produce artificial structuring in the water and affect diffusion rates. In cases where some form of short-range truncation must be used, the ST2 switching function applied on a group-by-group basis was found to be the most realistic procedure. If atom-based shifting must be employed, a cutoff distance greater than or equal to 12.0 angstrom was found to be required to produce realistic results.