SEAMM xnn Plug-in

A SEAMM plug-in providing machine-learned force fields (MLFFs) trained with xnn as model chemistries, run as MDI engines.

• Free software: BSD-3-Clause

• Documentation: https://molssi-seamm.github.io/xnn_step/index.html

• Code: https://github.com/molssi-seamm/xnn_step

History

2026.10.2 – Show what each model is, and pass the charge for D4 models

• The Model Chemistry step now describes each xnn model: its family (e.g. MACE), the elements it was trained on, and how dispersion enters it, e.g. “D4, 12 Å + tail added by the engine”. The plug-in reads this from the training configuration stored in the checkpoint, without PyTorch and without executing anything in the file.

• Models trained on dispersion-subtracted labels, which record the subtracted term as subtracted_dispersion in their training configuration, are recognized; the xnn mdi engine adds the term back by itself. A model that records the term and also carries a dispersion wrapper would count the dispersion twice. It is no longer offered, and asking for it by name is an error.

• For a charged configuration the total charge is now passed to the engine as --total-charge. D4 dispersion needs it for its EEQ partial charges.

2026.9.28 – Require xnns 0.4.0, which loads the existing checkpoints

• The environment now requires xnns>=0.4.0 instead of xnns<0.2. xnns 0.4.0 loads the checkpoints that 0.2.1 and 0.3.0 could not, and its engine supports --eeq-reuse. Updating the plug-in moves an existing environment to it, including one rolled back to 0.1.0 by hand; a torch built for the machine’s CUDA driver is kept, since xnns needs only torch 2.0 or later.

2026.9.27.1 – Local models can belong to the installation

• local: model directories in xnn.ini meant ~/SEAMM/data/Forcefields. They now mean the data/Forcefields directory of the SEAMM installation in use, then ~/SEAMM/data/Forcefields; a model in the installation’s own directory takes precedence. A second installation such as ~/SEAMM_DEV therefore sees the default installation’s models and can add its own.

• The SEAMM root now comes from seamm_util.current_root(), so an installation’s xnn.ini is found without --root. Requires seamm-util 2026.9.27.1.

2026.9.27 – Bugfix: pin xnns below 0.2 so existing checkpoints load

• The environment now requires xnns<0.2. The 0.2.1 and 0.3.0 releases on PyPI added scale_shift buffers to the MACE model with no defaults for older state dicts, so every existing checkpoint failed to load in the MDI engine (“Missing key(s) in state_dict: model.model.scale_shift.scale/shift”) and a LAMMPS run then hung waiting for it. A fresh installation was getting 0.3.0.

• Updating does not downgrade an environment that already has a newer xnns; run pip install xnns==0.1.0 in it by hand. The pin will move forward once an xnns release loads the older checkpoints.

2026.9.26 – Internal: depend on seamm-manager rather than seamm-installer

• The plug-in’s installer now builds on seamm-manager, which replaces seamm-installer for managing SEAMM installations. Nothing changes for users; this only lets the two packages stop being installed side by side.