Fast Multipole Method in Simulations of Aqueous Systems
IBM ALMADEN RESEARCH CENTER SAN JOSE CA
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The fast multipole method fmm for calculating electric fields developed by Greengard and Rokhlin J. Comp. Phys. 73, 3251987, has been implemented specifically for molecular dynamics simulations of electrochemical problems including boundary conditions associated with metal electrodes. This order N number of charged particles algorithm, is known to be computationally much more efficient than direct or Ewald sum methods order N 2 for systems with as few as one thousand charged particles equivalent to 300 water molecules. Timings and accuracy estimates with system size N 16 less than or N less than or equal 16000 are given to illustrate the effectiveness and efficiency of the fmm. As an application of fmm we describe its use with constant temperature molecular dynamics to calculate the dielectric constant of the space water model in bulk at temperatures 298K and 361K. System sizes of 27, 64, 125 and 216 water molecules were considered. Comparison with the Ewald and reaction field methods was made. At 298K the dielectric constant was calculated to be epsilon 75.5 or - 5 and at 361K epsilon 57.3 or - 4. Both values compare well with experiment and the reaction field theory simulations.
- Inorganic Chemistry
- Physical Chemistry
- Electricity and Magnetism