Features

• Evaluates the energy, gradients (forces) and, for periodic systems, the stress of the current configuration, every configuration of a system, or a selection by name.

• Uses whatever Model Chemistry precedes it in the flowchart – a machine-learned force field from the xnn plug-in, MOPAC, xTB, ORCA, … – provided it can be driven as an MDI engine.

• Starts the program once and feeds it the structures over the warm MDI connection, so labelling hundreds or thousands of structures (e.g. the ensembles from the Normal Mode Sampling, Dimer Builder or Extract Clusters steps) costs one start-up: ~14 ms per water molecule with an xnn MACE model on a laptop CPU.

• Stores the results on each configuration – energy#Energy#<model>, gradients#Energy#<model>, stress#Energy#<model> – and the gradients on the atoms, so the Write Structure step’s extended XYZ output carries REF_energy and REF_forces for training.

• Writes energies.csv (energy, max/RMS force and timing per structure) in the step’s directory and can save any result to variables or tables.

Acknowledgements

This package was created with Cookiecutter and the molssi-seamm/cookiecutter-seamm-plugin project template.

Developed by the Molecular Sciences Software Institute (MolSSI), which receives funding from the National Science Foundation under award ACI-1547580

2026.10.3 (2026-10-03)

• The structures can now run as separate calculations as well as over an MDI engine; SEAMM chooses. ORCA runs them as separate calculations, several at a time, and with a job whose calculations go to a cluster queue, ORCA and MOPAC run them there. MLFFs, xTB and MOPAC on this machine keep the warm MDI engine. The numbers are the same either way.

• Separate calculations are kept in tasks/c<id>/; rerunning the job reuses the finished ones.

• A structure the program cannot run as a separate calculation (a periodic system for ORCA or MOPAC) goes to its MDI engine, and the output says how many went each way. If some structures fail, the others are still stored and the step then stops, listing the failures.

• A configuration selected twice is evaluated once.

• The shared CI now runs on uv: devtools/conda-envs/test_env.yaml is removed, so requirements.txt is the one dependency list.

• Requires seamm-exec 2026.10.3 or later.

2026.9.19 (2026-09-19)

• Structure selection now uses SEAMM’s standard block (systems and configurations, by name or from a variable), so the Energy step can e.g. evaluate all configurations of every system, or the systems matching a pattern.

• The output states exactly what was stored on each configuration (energy, gradients, stress) and mentions forces only when they were calculated; the CSV summary is secondary.

• The output names the model file used when the provider reports one, e.g. personal:xnn/water.pt, so a personal model shadowing a machine one is visible.

• Requires seamm 2026.9.18.1 or later.

2026.9.18 (2026-09-18)

• Initial release. Evaluates the energy, gradients and (periodic) stress of one or many configurations with the upstream Model Chemistry driven as a resident MDI engine; results stored per configuration and on the atoms, with energies.csv and table/variable output. Validated with an xnn MACE model (1000 water configurations in 14 s) and with MOPAC PM6-ORG.

• Plug-in created using the SEAMM plug-in cookiecutter.