Dresden 2020 – scientific programme

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O: Fachverband Oberflächenphysik

O 124: Development of Novel Methods II

O 124.9: Talk

Friday, March 20, 2020, 12:30–12:45, WIL C107

Reliable electrostatic energies in MPE implicit solvation — •Jakob Filser, Konstantin Jakob, Markus Sinstein, Karsten Reuter, and Harald Oberhofer — Technical University of Munich

Implicit solvation models like the multipole expansion (MPE) model [1] are widely used in first-principles calculations to incorporate solvent effects without the necessity of sampling solvent degrees of freedom. MPE divides the free energy of solvation into the electrostatic interaction between the solute and a dielectric medium, and a remaining, ‘nonelectrostatic’ term, fitted to experimental reference data. The medium is defined to fill all space outside a ‘cavity’ around the solute.

In the present work, we solve two shortcomings of the state-of-the-art treatment of electrostatic interactions in MPE: First, for larger and more complex solutes the multipole basis for the potential becomes insufficient to solve the electrostatic problem. Currently, this is partially compensated for in the nonelectrostatic energy contribution. However, an accurate solution which does not rely on such error cancellation is obviously more desirable. We achieve this by dividing space into approximately spherical domains inside each of which a multipole basis is sufficient to express arbitrary harmonic potentials.

Second, the shape of the cavity crucially influences the electrostatic interaction, but there is no unique and straightforward definition of the cavity. This can lead to a systematic error in the electrostatic interaction. As a remedy, we choose a cavity definition which – at least on average – neither over- nor underestimates this term.

[1] M. Sinstein et al., J. Chem. Theo. Comput. 13, 5582, 2018.