Newest CHARMM36 port for GROMACS

We are pleased to announce an updated port of the CHARMM36 force field for GROMACS, available at

The July 2020 release corresponds to the annual update to the CHARMM36 force field. Notable revisions include:

  1. NBFIX terms for K+ and Ca2+ ions with carboxylates
  2. New nucleic acid model compounds
  3. CGenFF version 4.4, including amide base model compounds, boronic acid and bicyclic boron “ester” model compounds and associated parameters

Please let me know if you encounter any problems using the force field. Happy simulating!

Contact person (name and email address): Justin Lemkul (

How the work has been tested/reviewed: Forces and energies have been compared between CHARMM and GROMACS for a set of isolated molecules (gas phase) including all amino acids, nucleotides, a subset of lipids and other compounds