Figure 2.

Workflow for developing ff15ipq force field parameters. Starting from a model consisting of multiple coordinate and topology files, the IPolQ charge derivation protocol is used to fit atomic charges from electrostatic potential calculations in both vacuum and explicit solvent phases. These charges are averaged, implicitly modeling solvent polarization effects. The vacuum-phase charges are used to fit bonded parameter terms to the vacuum-phase QM targets and used iteratively with the implicitly polarized charges, as indicated by the gray arrows, to generate a new initial model until the parameters are self-consistent.