# Best practice for using newer AMBER force fields (ff19SB) in GROMACS? **URL:** \ **Category:** User discussions\ **Tags:** forcefield, simulation-setup\ **Created:** [November 17, 2025, 7:07pm UTC](https://gromacs.bioexcel.eu/t/best-practice-for-using-newer-amber-force-fields-ff19sb-in-gromacs/12942 "2025-11-17T19:07:02Z")\ **Posts on this page:** 4\ **Page:** 1
**Author:** ![ehsan](https://dub1.discourse-cdn.com/flex017/user_avatar/gromacs.bioexcel.eu/ehsan/32/1345_2.png) [@ehsan](https://gromacs.bioexcel.eu/u/ehsan)\ **Post date:** [November 17, 2025, 7:07pm UTC](https://gromacs.bioexcel.eu/t/best-practice-for-using-newer-amber-force-fields-ff19sb-in-gromacs/12942/1 "2025-11-17T19:07:02Z")
GROMACS version: 2024.4 Hi everyone, What is currently the _best_ way to use a newer AMBER force field such as **ff19SB** in GROMACS? I’m aware of the approach where you convert the AMBER parameter files to GROMACS format using **ParmEd**. However, when I use ParmEd-converted ff19SB in my protein–ligand + water simulations, I observe some strange behavior: - a vacuum “cylinder” or cavity forms in the center of the simulation box, and - the MM/PBSA results show **no correlation** with equivalent simulations run in **NAMD** using the same force field. I know that CHARMM-GUI can generate GROMACS-ready systems with AMBER force fields, including ff19SB, but I’m looking for a solution I can run **locally** , integrate into a **pipeline** , and avoid relying on a web interface. Has anyone successfully and reliably used ff19SB in GROMACS with fully local tools? Any recommended workflows, conversion scripts, or known pitfalls with ParmEd I should be aware of? Thanks in advance! ---
**Author:** ![milosz.wieczor](https://avatars.discourse-cdn.com/v4/letter/m/b19c9b/32.png) [@milosz.wieczor](https://gromacs.bioexcel.eu/u/milosz.wieczor)\ **Post date:** [November 19, 2025, 11:41am UTC](https://gromacs.bioexcel.eu/t/best-practice-for-using-newer-amber-force-fields-ff19sb-in-gromacs/12942/2 "2025-11-19T11:41:47Z")
Vedran Miletić @vedran is currently working on the official ff19SB port for Gromacs, and the reasons things are not as straightforward as ParmEding the topology are explained e.g. in his post below: > **[Webinar #81: What’s new in GROMACS 2025 | Vedran Miletić](https://www.linkedin.com/posts/vedranmiletic_webinar-81-whats-new-in-gromacs-2025-activity-7298265046638321664-yAd5/)** > > 🚀 Excited to share that recently released #GROMACS 2025 now includes support for per-amino-acid CMAPs, a feature developed by a team that I am a part of! This is a requirement for bringing the Amber ff19SB force field to GROMACS users, which is the... I believe they should be advanced enough to have an experimental version running, but he’d have to tell you if it’s shareable at this point. ---
**Author:** ![vedran](https://dub1.discourse-cdn.com/flex017/user_avatar/gromacs.bioexcel.eu/vedran/32/1784_2.png) [@vedran](https://gromacs.bioexcel.eu/u/vedran)\ **Post date:** [November 19, 2025, 1:57pm UTC](https://gromacs.bioexcel.eu/t/best-practice-for-using-newer-amber-force-fields-ff19sb-in-gromacs/12942/3 "2025-11-19T13:57:04Z")
Hello. As @milosz.wieczor suggested, the endeavor is non-trivial, but we are progressing. His work on Gromologist was very helpful to get started. - Per-amino-acid CMAP support appeared in 2025: [New and improved features - GROMACS 2026.0-dev-20251118-ff0e9730 documentation](https://manual.gromacs.org/nightly/release-notes/2025/major/features.html#support-for-amino-acid-specific-energy-correction-maps-cmaps) - LEaP-compatible dihedral atom reordering is accepted for 2026: [New and improved features - GROMACS 2026.0-dev-20251118-ff0e9730 documentation](https://manual.gromacs.org/nightly/release-notes/2026/major/features.html#added-leap-compatible-dihedral-reordering) As the last step, GROMACS will get the converted force field files. We are still going through the validation (and making changes) internally on a larger set of molecules. Therefore, the current version of the force field is not yet public, but we hope it will be ready for release sometime soon. ---
**Author:** ![vedran](https://dub1.discourse-cdn.com/flex017/user_avatar/gromacs.bioexcel.eu/vedran/32/1784_2.png) [@vedran](https://gromacs.bioexcel.eu/u/vedran)\ **Post date:** [December 17, 2025, 2:35pm UTC](https://gromacs.bioexcel.eu/t/best-practice-for-using-newer-amber-force-fields-ff19sb-in-gromacs/12942/4 "2025-12-17T14:35:26Z")
@ehsan please take a look at [GROMACS 2026 release candidate](https://gromacs.bioexcel.eu/t/gromacs-2026-release-candidate/13047)