Abstract
Describing long-ranged electrostatics using short-ranged pair potentials is appealing because the computational complexity scales linearly with the number of particles. The foundation of the approach presented here is to mimic the long-ranged medium response by cancelling electric multipoles within a small cutoff sphere. We propose a rigorous and formally exact new method that cancels up to infinitely many multipole moments and is free of operational damping parameters often required in existing theories. Using molecular dynamics simulations of water with and without added salt, we discuss radial distribution functions, Kirkwood–Buff integrals, dielectrics, diffusion coefficients, and angular correlations in relation to existing electrostatic models. We find that the proposed method is an efficient and accurate alternative for handling long-ranged electrostatics as compared to Ewald summation schemes. The methodology and proposed parameterization are applicable also for dipole–dipole interactions.
Highlights
Accurate and efficient schemes to calculate long-ranged electrostatic interactions are important to expand time and space in atomistic simulations
To evaluate the developed q-potential, we investigate a bulk water system and an aqueous salt solution by analyzing, among others, radial distributions functions, angular correlations, and KB integral (KBI)
The Ewald/PME methods assume a replicated environment and may not necessarily represent a true isotropic system,[24,39] we choose this as a reference system because of its widespread use in molecular simulations
Summary
Accurate and efficient schemes to calculate long-ranged electrostatic interactions are important to expand time and space in atomistic simulations. One of the earliest schemes is the reaction field method[1,2] where a spherical cutoff, Rc, is applied. To correctly parameterize the reaction field method, the surrounding dielectric constant, εRF, needs to be estimated, and artifacts may arise because of discontinuities at the cutoff.[3] Lattice approaches, including the Ewald method,[4,5] provide an accurate electrostatic description within a wellknown parameter space[6,7] but are inherently limited to periodic systems. The computational complexity of Ewald is 6(52) but reduces to 6(53/2) with optimal parameters This growing cost with increasing system size makes Ewald methods demanding for large systems, albeit derived versions such as Particle Mesh Ewald[8] (PME) has improved 6(5 log 5) scaling
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