The influence of solvents on elementary physicochemical processes on catalysts or in batteries is a challenge for theoretical modeling. The natural approach of explicitly describing the solvent molecules and calculating properties of the overall system as ensemble quantities is numerically too expensive for most applications. This is especially the case when rare events such as reactions are to be described or the influence of low-concentration electrolytic ions is to be modeled.
For this reason, implicit solvation models are often used, in which a given solvent is parameterized by a few parameters.

We have recently implemented such an implicit model, based on the Poisson-Boltzmann model, in the electron structure program Q-Chem and are currently extending this model to include analytical gradients for structure optimization. This project is a collaboration with Martin Head-Gordon's group at Berkeley and originated during Christopher's postdoctoral period.

In future projects, we want to link this model with our other developments in the field of energy materials and also investigate mixed implicit/explicit solvent models.

The latter work is supported by the Cluster of Excellence RESOLV.

Publications:

C. J. Stein, J. M. Herbert, M. Head-Gordon, The Poisson–Boltzmann model for implicit solvation of electrolyte solutions: Quantum chemical implementation and assessment via Sechenov coefficients, J. Chem. Phys. 151, 2019 224111.