Efficient Handling of Gaussian Charge Distributions: An Application to Polarizable Molecular Models

We present a mesh-based Ewald summation method that is suitable for the calculation of the electrostatic interaction between Gaussian charge distributions, instead of point charges. As an application, we implemented the method in the Gromacs simulation package and tested it with a polarizable water model, showing that the interaction between Gaussian charge distributions can be computed with a small (10%) additional computational cost with respect to the point charge case. In addition, since the performance of polarizable models is strongly influenced by the number of iterations required for the self-consistent field solution, we tested also the Always Stable Predictor-Corrector (ASPC) method of Kolafa (Kolafa, J. J. Comp. Chem. 2003, 25, 335) as an alternative to the steepest descent (SD) based algorithm with predictor implemented in the Gromacs, and found that it speeds up the integration of the equations of motion by a factor of 1.6-2.0, depending on the target model.