New approach to instantaneous polarizable electrostatic embedding of the solvent

The sequential quantum mechanics/molecular mechanics (S-QM/MM) method efficiently computes solvent effects on the electronic properties of solutes. The protocol involves two steps: solute-solvent configurations are generated from MM simulations, while the solute properties are computed in the subsequent QM step. A well-known difficulty within the S-QM/MM framework is the description of the polarization of the MM partition (electrostatic embedding) in case the electronic structure of the solute undergoes sudden changes, such as in electronic excitation, electron attachment or detachment processes. To improve the description of the electronic polarization of the solvent, we propose the self-consistent S-QM/MM polarizable electrostatic embedding (scPEE-S-QM/MM) method, which generates individual atomic charges for the solvent molecules due to solute-solvent and solvent-solvent polarization. The electronic properties calculated for the neutral and anion states of 1-methyl-4-nitroimidazole were found to be significantly affected by solvent polarized electrostatic embeddings obtained for different solute electronic states. Finally, the method also provides accurate results for bulk water.