Solvation Free Energies in Subsystem Density Functional Theory

For many chemical processes the accurate description of solvent effects are vitally important. Here, we describe a hybrid ansatz for the explicit quantum mechanical description of solute-solvent and solvent-solvent interactions based on subsystem density functional theory and continuum solvation schemes. Since explicit solvent molecules may compromise the scalability of the model and transferability of the predicted solvent effect, we aim to retain both, for different solutes as well as for different solvents. The key for the transferability is the consistent subsystem decomposition of solute and solvent. The key for the scalability is the performance of subsystem DFT for increasing numbers of subsystems. We investigate molecular dynamics and stationary point sampling of solvent configurations and compare the resulting (Gibbs) free energies to experiment and theoretical methods. We can show that with our hybrid model reaction barriers and reaction energies are accurately reproduced compared to experimental data.

Automated summary

The accurate description of solvent effects is crucial for many chemical processes. In this study, we propose a hybrid approach based on subsystem density functional theory and continuum solvation schemes for the explicit quantum mechanical description of solute-solvent and solvent-solvent interactions. Our model incorporates consistent subsystem decomposition for transferability and demonstrates good scalability for increasing numbers of subsystems. By comparing the resulting free energies to experimental data, we show that our hybrid model accurately reproduces reaction barriers and energies.