History

2026.10.3 – Initial release: many-body expansion (MBE) corrections

• A step that estimates high-level energies, forces and, for periodic cells, the stress of a cell or a large cluster: a low-level calculation of the whole system plus [high - low] corrections computed on monomers, pairs and triples of molecules, using the seamm_mbe library.

• The levels are model chemistries: the high level, a molecular low level, and optionally a periodic low level (e.g. VASP) for the fragments of periodic cells, run as batches of calculations through seamm_exec.

• Pair and triple cutoffs, a rule for which triples to include, and a check that the cell is large enough for the chosen cutoffs.

• For a periodic low level, the fragments are placed on the cell’s FFT grid so that the grid errors cancel between the cell and its fragments.

• Optional pairwise counterpoise correction of the basis-set superposition error.

• Optional energy offsets per molecule type, and the results stored as properties and written to an extended XYZ file for training machine-learned force fields.