MOLECULAR-DYNAMICS SIMULATIONS OF WATER WITH EWALD SUMMATION FOR THE LONG-RANGE ELECTROSTATIC INTERACTIONS

The use of a partial charge version of the Ewald sum method to treat long range electrostatic interactions in molecular dynamics simulations of water has been investigated. The orientational structure and energetic properties of the liquid have been studied for several choices of Ewald sum parameters. The results, including the dielectric constant epsilon-o, the radial-dependent Kirkwood factor G(k)(r), the orientational projection H-DELTA-(r), and the average dipole interaction energy, are compared with those from molecular dynamics simulations of water using the reaction field method. While the orientational structure of the liquid obtained from simulations which treat long range interactions by Ewald summation is different from corresponding results obtained from simulations with a reaction field, consistent values are calculated for the dielectric constant. The sensitivity of the results to variations in the convergence parameter alpha, the real-space cutoff R(c), and the number of vectors used in the reciprocal space sum was also analyzed.