GROMACS 2026.5 release notes¶
This version was released on TODO, 2026. These release notes document the changes that have taken place in GROMACS since the previous 2026.4 version, to fix known issues.
Fixes where mdrun could behave incorrectly¶
Fixed incorrect LJ-PME forces and energies for perturbed particles¶
In the free-energy non-bonded kernel, the indexing of the coefficient buffer for LJ-PME grid corrections was incorrect. This meant that forces and energies were incorrect. In addition, the coefficient buffer for LJ-PME grid corrections was not allocated sufficiently large, which meant that LJ forces and energies could be random, depending on whether the memory accessed was used for other data. And finally, the PME grids were mixed up for computing the B-state forces and energies. These issues have been present in versions 2025.0 to 2026.4.
Issue 5716 Fix incorrect virial and pressure with perturbed atoms “”””””””””””””””””””””””””””””””””””””””””””””””””””””
With free-energy calculations, perturbed non-bonded interactions would have incorrect virial contributions when interacting over a periodic boundary. This led to incorrect pressures. The effect would be small when only a few atoms were perturbed. This bug has been present in release 2025.0 to 2026.4.
Fixed the exclusion check of free energy calculations with multiple molecule types¶
In free energy calculations with Ewald, PME or LJ-PME, mdrun checks that the number of perturbed excluded pairs found in the pair search matches the number expected from the topology. When the inter-molecular exclusion group contained atoms of different molecule types, the expected number used the perturbation state of an atom from the wrong molecule type. This could cause a spurious fatal error, could let the check pass although perturbed excluded pairs were beyond the pair-list cut-off, or could read memory beyond the end of the atom data. This has been present in versions 2026.0 to 2026.4.
Fixes for gmx tools¶
Fixed grompp crash with deform-init-flow for integrators without velocities¶
With deform-init-flow = yes, gmx grompp crashed with a segmentation
fault for energy minimization, normal-mode analysis and test-particle insertion,
since these integrators do not use velocities. Now deform-init-flow is
ignored with these integrators, with a note when deform is set. With these
integrators, gmx grompp also no longer asks for
deform-init-flow = yes when the box is deformed. With integrator = bd,
which does not use the initial velocities, the error for gen-vel = yes
without deform-init-flow = yes is now a warning and the note asking for
deform-init-flow = yes is no longer given. This has been present in versions
2024.0 to 2026.4.