ABSTRACT
This work proposes an approach to calculate long-range interactions for molecular modeling and simulation. Based on the isotropic character of homogenous systems, for each particle this method describes a molecular system as a local region around the particle and many images of the local region distributed on shells around the particle. The isotropic and periodic distribution of these images makes the summation of long-range interactions over all images an easy task, which we call the isotropic periodic sum (IPS). Analytic solutions of IPS for electrostatic and Lennard-Jones potentials have been worked out. The same approach can be applied to potentials of any functional form and to any type of periodic systems. Using an argon fluid and a CaCl2 ionic system, we demonstrate that the IPS method gives very close results to lattice sum. For macromolecular systems, this method is better than lattice sum by avoiding the symmetry imposed from periodic boundary conditions. For non-periodic systems, IPS is better than cutoff methods if the system size is large.
