Direct summation of dipole-dipole interactions using the Wolf formalism

We present an expanded Wolf formalism for direct summation of long-range dipole-dipole interactions and rule-of-thumbs how to choose optimal spherical cutoff (R-c) and damping parameter (alpha). This is done by comparing liquid radial distribution functions, dipole-dipole orientation correlations, particle energies, and dielectric constants, with Ewald sums and the Reaction field method. The resulting rule states that alpha sigma < 1 and alpha R-c > 3 for reduced densities around rho* = 1 where sigma is the particle size. Being a pair potential, the presented approach scales linearly with system size and is applicable to simulations involving point dipoles such as the Stockmayer fluid and polarizable water models. (C) 2015 AIP Publishing LLC.