Core choices
| Setting | Meaning | Check before running |
|---|---|---|
| Functional | Exchange-correlation approximation. | Use pseudopotentials and a solver workflow compatible with it; UI selection alone does not establish method support for every advanced case. |
| ecutwfc / ecutrho | Plane-wave wavefunction and charge-density cutoffs. | Converge the reported energy, forces, stress, or response; respect pseudopotential recommendations. |
| k-point mesh | Sampling for Brillouin-zone integration. | Use a uniform mesh for SCF/DOS; do not substitute a high-symmetry band path. |
| Occupations / smearing | How electronic states are filled and integrated. | Match metallic, insulating, spin, and temperature assumptions. |
| nbnd | Number of computed bands. | Include enough unoccupied states for the target energy window or transport analysis. |
| SCF thresholds / mixing | Self-consistency stopping and iteration behavior. | Inspect convergence; raising the iteration limit does not fix every physical or numerical instability. |
| Charge / magnetization / spin | Electronic state assumptions. | Use compatible pseudopotentials and a justified reference state. |
Adaptive and expert modes
Adaptive mode resolves editable occupation and cutoff defaults from the workflow and material context. User overrides remain explicit.
Expert raw input is authoritative for the submitted text. Adaptive occupation and cutoff resolution does not silently rewrite it. You take responsibility for compatible cards, paths, species, units, and solver options.
Review the executed input from the result artifacts, not only an earlier editor preview. The worker may resolve required runtime data such as pseudopotential provenance.
Convergence example
- Fix one structure and method; create a baseline Total energy calculation.
- Vary ecutwfc and the compatible ecutrho while keeping the k mesh fixed.
- Track energy per atom and, when relevant, forces or stress instead of only total cell energy.
- Choose a sufficient cutoff, then vary the k mesh.
- For low-dimensional systems, repeat the vacuum check independently.
- Record the tolerance used to call the reported quantity converged.