Rowan Docs

Spin State Prediction

Python API · stjames models · API example

How it works

Compare the electronic energies and optimized structures of a molecule at the spin multiplicities you specify. Rowan optimizes each multiplicity independently from the same input geometry, then evaluates a final single-point energy if the selected protocol includes one. The lowest energy identifies the favored state among the states successfully calculated with that protocol.

Settings

  • Spin states: enter comma-separated positive multiplicities, such as 1, 3, 5 (singlet, triplet, quintet). Use odd multiplicities for an even electron count and even multiplicities for an odd electron count; the molecular charge affects that count.
  • Multistage opt. settings: choose a preset or edit the optimization stages and final single-point method. The web default is GFN2-xTB optimization followed by r²SCAN-D4/vDZP energy.
  • Solvent (all steps): choose an implicit solvent for supported stages, or leave empty for gas phase. Individual stages can also have separate solvent settings.
  • Calculate frequencies?: calculate vibrations at the final optimization level to check the stationary point and obtain thermochemical corrections.
  • Transition state?: optimize a transition state at each multiplicity instead of a minimum. Start from a suitable transition-state guess.
  • Constraints: optionally hold selected coordinates fixed during optimization; check support for the selected methods.

Preset protocols

PresetOptimization stages (in order)Final single-point method
RecklessGFN-FFGFN2-xTB
RapidGFN2-xTBr²SCAN-D4/vDZP
Carefulr²SCAN-D4/vDZPωB97X-3c
Meticulousr²SCAN-D4/vDZP → ωB97X-3cωB97M-D3(BJ)/def2-TZVPPD

Notes

The results table reports energy differences in kcal/mol relative to the lowest calculated state. Select a row to inspect its structure or use "Overlay spin states" to compare geometries. Open the linked calculation to inspect its details.

The ranking uses electronic energies, including when frequencies are requested. Thermal corrections do not automatically turn this table into a free-energy comparison. Review convergence and frequency warnings, and confirm that every requested state produced a result before interpreting the ranking.

The workflow explores the requested multiplicities from one starting geometry, rather than searching all conformations or electronic configurations. Energy gaps depend on the method and geometry; closely spaced states warrant further checks with an appropriate alternative method. All stages must support the molecule's elements and charge.

Submission video

Further reading