Atoms stores the system; the calculator supplies results
ASE connects its central Atoms object to calculators implementing scientific methods. Atoms carries species, positions, cell, periodicity and constraints; an attached calculator provides the requested supported properties. SevenNet and MACE document ASE calculators, while CHGNet documents ASE-based dynamics and relaxation. This common interface helps orchestration but does not make their potential surfaces, checkpoints or supported properties identical. Confirm the chosen calculator implementation before interpreting energy, forces or stress.
ase-calculators · seven-README.md · mace-README.md · chg-README.md
Units belong to the interface
ASE defines eV and Å as base units, and optimization logs report energy in eV and maximum force in eV/Å. Stress uses energy per volume, so record conversion to or from GPa together with sign and component conventions. CHGNet direct prediction uses eV/atom for energy and GPa for stress; its raw prediction dictionary is not an ASE energy/stress result. Check whether an adapter already converts values before applying another conversion. Preserve atom order and distinguish total energy from per-atom quantities.
ase-units · ase-optimize · chg-README.md
Fixed cell and relaxed cell answer different questions
Optimizing atomic positions at a fixed cell searches within that cell constraint. Variable-cell relaxation introduces cell degrees of freedom through an appropriate ASE filter and requires valid stress support. ASE documents FrechetCellFilter for combining atomic forces and cell stress. Do not add a cell filter merely because an optimizer is available: choose fixed shape, fixed volume or cell relaxation according to the physical question. Record periodic boundaries, constraints, pressure targets and the actual properties requested from the calculator.
Convergence is a numerical condition
ASE local optimizers seek a nearby minimum and expose a force threshold fmax. A threshold reached within a model means the selected numerical stopping criterion was met; it is not evidence of global optimality, DFT accuracy, dynamical stability or correct phase ordering. A run may also stop at a step limit. Retain the convergence result, final forces, trajectory and warning log rather than calling every produced structure “optimized.” Inspect severe distortions and non-finite values before comparing energies.
Validate the model in the intended domain
Plan reference single-point calculations at the initial and relaxed geometries using a consistent method, and compare forces and relevant energy differences. If MD is the intended application, plan a separate trajectory/stability evaluation; a geometry relaxation is not its substitute. Record elements, charge/spin assumptions where relevant, cell, training-domain fit, checkpoint hash, code version, precision, constraints and convergence settings. Pin the SevenNet checkpoint and calculator revision because documented pretrained families evolve. This is a validation plan, not a report of calculations performed.
Related resources and reading
ASE · SevenNet · MACE · CHGNet
Fixed-Cell Crystal Relaxation with SevenNet and ASE
Preparing an atomistic potential evaluation · AI for Computational Chemistry Workflows · Chemistry & Materials AI Skills: RDKit, Datamol, ASE, Phonopy and More
Sources and evidence boundary
Sources were inspected on 2026-10-08. Revision-pinned project documentation supports capability statements. Evaluation choices are editorial proposals. This article reports no executed workflow, measured performance, or experimental validation.