Energy

The Energy sub-step runs a single xTB calculation at the current geometry and reports the total and electronic energies, HOMO and LUMO energies (when xTB provides them), the HOMO-LUMO gap, the dipole moment, and the atomic partial charges.

It does not change the geometry.

Dialog

Opening the Energy sub-step shows a single panel labelled Hamiltonian Parameters containing the following controls:

xTB method

The Hamiltonian or force field to use. Defaults to GFN2-xTB. See Methods for guidance on choosing among the GFN family.

Accuracy

The xTB --acc multiplier. The default of 1.0 is appropriate for most calculations. Smaller values tighten integral and SCC convergence; larger values loosen them. Useful range is roughly 0.0001 to 1000.

Implicit solvation

The solvation model: none (default), ALPB, GBSA, or CPCM-X. See Solvation for details on each model and the supported solvents.

Solvent

The solvent for implicit solvation. Hidden when the solvation model is none. Visible (and indented) when a solvation model is selected. Defaults to H2O.

Charge and spin multiplicity are read from the current configuration and do not appear in the dialog. They are set when the structure is built (e.g. in the From SMILES step).

Output

The Energy sub-step prints a results table to step.out like the example below:

                    xTB (GFN2-xTB) Results
╭─────────────────────────────────────────────────────┬───────────┬───────╮
│                      Property                       │   Value   │ Units │
├─────────────────────────────────────────────────────┼───────────┼───────┤
│                  The total energy                   │ -5.069275 │  E_h  │
│ The electronic energy (excluding nuclear repulsion) │ -5.096007 │  E_h  │
│                  The HOMO-LUMO gap                  │ 13.1714   │  eV   │
│        The molecular dipole moment magnitude        │  2.2109   │ debye │
╰─────────────────────────────────────────────────────┴───────────┴───────╯

The same quantities are stored as properties of the configuration in the SEAMM database, under names like total energy#xTB#GFN2-xTB (the model is substituted at run time). See Results for the full list.

The work directory for the sub-step also contains the raw xTB files: coord.xyz (input), xtb.out (full xTB output), xtbout.json (structured output), xtbtopo.mol (topology), and xtbrestart (restart file).