• ForceBalance: A versatile package for force field optimization • GeomeTRIC: Geometry optimizer for molecular structures with translation-rotation-internal coordinate (TRIC) system 64 • Nonbonded: Automated workflow for the optimization and assessment of the non-bonded interaction parameters of force fields against physical property datasets 65 • OpenFF-Toolkit: Chemistry toolkit for working with SMIRNOFF format force fields, as well as interface to various cheminformatics back-ends (RDKit 66 and OpenEye ), and molecular dynamics engines (OpenMM) • OpenFF-QCSubmit: Dataset building, validation, and data retrieval from QCArchive • OpenFF-Evaluator: Automated and highly scalable physical property evaluator • OpenFF-BespokeFit: Processing QCArchive data and creating ForceBalance inputs • OpenMM: High performance molecular dynamics package with a variety of enhanced sampling methods 71 • PMX: Toolkit for free-energy calculation setup/analysis and biomolecular structure handling • Psi4: Highly parallel electronic structure code covering a large range of methods, density functional/basis set combinations, and property evaluations 73 • QCEngine: A common Python interface to various Quantum Chemistry packages • QCFractal: Server for facilitating Quantum Chemistry calculations on large compute clusters and archiving the results in a database Hydrogen attached to trivalent carbon attached to two electronegative atoms