In QM/MM calculations, it is essential to describe electrostatic interactions between the QM and MM subsystems accurately, and there exist a whole spectrum of algorithms for treating electrostatic/polarization effects. On one end, QM/MM Ewald summation method is the state-of-the-art way for handling the QM/MM electrostatic interaction, but it is non-trivial to implement and requires modifications of the QM codes. On the other end, it is common to truncate QM/MM electrostatic interactions at a certain cutoff distance without using a switching function. This simple distance cutoff causes discontinuity on the potential energy surfaces, which can lead to artifacts in QM/MM molecular dynamics simulations under periodic boundary conditions. When a switching function is applied to QM/MM electrostatic interactions, it smooths the energy at the cutoff distance but it also perturbs the MM electrostatic potential for the QM subsystem in a way that is not yet fully analyzed. In this study, we separated the QM/MM electrostatic interactions into two parts: electrostatic forces and polarizations, and benchmarked the influences from different switching functions and cutoff distance values, with QM/MM Ewald summation method employed as the reference. We hope this study can help the community in developing the best practice for choosing the optimal cutoff parameters to treat electrostatic interactions in QM/MM molecular dynamics simulations.

Benchmarking of electrostatic interactions in QM/MM molecular dynamics simulations

254th National Meeting (2017)

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