New and improved features¶
Collective variables module (Colvars) update¶
The (Colvars) library for enhanced sampling simulations included in GROMACS has been updated to version 2025-10-13.
This update brings many improvements, including: - performance improvements for moving frame of reference calculations - improved OPES implementation - improved moving restraint logic, allowing for moving harmonic walls - more flexible definitions of grids on CVs A complete list of changes can be found here.
For documentation see this section of the GROMACS doc along with the Colvars documentation page dedicated to GROMACS 2026. Messages about Colvars in the GROMACS discussion forum should be tagged with the colvars keyword for easier consultation.
Added LEaP-compatible dihedral reordering¶
AMBER LEaP reorders (improper) dihedrals when processing the topology, alphabetically
by atom type. In order for GROMACS to be able to match the topology produced by LEaP,
gmx grompp was extended LEaP-compatible dihedrals reordering. This functionality
is intended for usage with the ports of recent AMBER force fields (e.g. ff14SB and
ff19SB), but it is enabled on any force field that defines the
_FF_AMBER_LEAP_ATOM_REORDERING macro.
This feature has been validated on all supported dipeptides and tripeptides as well as select tetrapeptides and pentapeptides. Systematic validation on a broader set of scientifically relevant biomolecules is still pending.
Improved implementation of the neural network potential interface¶
The neural network potential (NNP) interface has been extended to support new model inputs. Firstly, it is now possible to use a list of atom pairs within the NNP region filtered by a user-specified cutoff, as well as corresponding periodic shift vectors, as an input to the NNP. This enables the use of model architectures such as SchNet or MACE and re-uses the pair-list generated by GROMACS. Secondly, we also add support to pass positions and charges of the MM region around the NNP region to the model, enabling the use of electrostatic embedding schemes such as implemented in EMLE. Furthermore, a link atom scheme is now employed to treat covalent bonds between the NNP and MM regions. In addition, there have been minor performance improvements, and the interface now supports both CUDA and ROCm/HIP-builds of LibTorch. For more details on the supported features and usage, please see the NNPot section in the reference manual.
Added support for H5MD trajectory file format¶
Trajectory data can now be written to the H5MD file format by gmx mdrun. Data written to this file format includes positions, velocities, forces, and the simulation box. Chemical bonds are also written to the connectivity group. For this release, only lossless output is supported.
Note that support for this file format in GROMACS tools is experimental. Analysis tools are able to read all files but bugs should be expected. H5MD output from gmx trjconv and gmx trjcat is not implemented.