The parameter optimization was carried out with ForceBalance, a Python toolkit to optimize force fields in a systematic, reproducible, scalable and flexible manner. We employed a development version of ForceBalance based on v1.6.0 ) to minimize the objective function. Support of the OpenFF force field was enabled by an interface with the OpenFF Toolkit v0.4.1. The commercial OpenEye toolkit version 2019.4.2 was used to generate .mol2 files, which are needed by ForceBalance to set up OpenFF simulations using the toolkit.