Force field for biomolecular simulations of chlorine and hypochlorous acid with accurate solvation energies

Molecular mechanical models for chlorine (Cl2) and hypochlorous acid (HOCl) are presented as extensions of GROMOS-RONS, a classical force field originally developed for simulations of reactive oxygen and nitrogen species (RONS). For Cl2, new Lennard–Jones parameters were introduced. Addition of a quadrupole accounted for σ-hole formation and halogen bonding, yielding accurate solvation free energies both in water and hydrocarbons. For HOCl, partial atomic charges were iteratively adjusted to match experimental hydration free energy with high accuracy. These parameters enable studies of partitioning of reactive halogen species at biological interfaces relevant to disinfection and plasma/redox therapies.