CALCULATING ELECTROSTATIC INTERACTIONS USING THE PARTICLE-PARTICLE PARTICLE-MESH METHOD WITH NONPERIODIC LONG-RANGE INTERACTIONS

The particle-particle particle-mesh (PPPM) method is an accurate and c omputationally efficient method for calculating interactions in molecu lar simulations. The PPPM method is based on separating the total inte raction between particles into the sum of short-range interactions, wh ich are computed by direct particle-particle summation, and long-range interactions, which are calculated by solving Poisson's equation usin g periodic boundary conditions (PBCs). For nonperiodic systems there i s a concern that use of PBCs may introduce an artificial periodicity i nto the system. In this article we propose, and test, the use of bound ary conditions for the long-range interactions which mimic surrounding the explicit system by high dielectric material such as water.