SKILL.md
TB2J Skill
This skill provides expert guidance on using the TB2J package to calculate magnetic interaction parameters (Heisenberg exchange $J$, DMI $D$, Anisotropy $J_{ani}$) from DFT inputs.
References
- [Command Reference](references/commands.md): Detailed flags and arguments for all scripts (
wann2J.py,siesta2J.py, etc.). - [Workflows & DFT Prep](references/workflows.md): Step-by-step guides for preparing VASP/Wannier90/Siesta inputs.
- [Conventions](references/conventions.md): Vital information on Hamiltonian signs, units, and spin normalization.
- [Outputs](references/outputs.md): Explanations of
exchange.out,exchange.xml, and interfaces to Vampire/Multibinit.
Common Workflows
1. Wannier90 (VASP, QE, Abinit)
- Command:
wann2J.py - Key Step: Ensure
projectionsin.winfile cover magnetic orbitals. - See: [Workflows > Wannier90](references/workflows.md#1-wannier90-workflow-general)
2. Siesta
- Command:
siesta2J.py - Key Step: Set
SaveHS Truein.fdf. - See: [Workflows > Siesta](references/workflows.md#2-siesta-workflow)
3. Abacus
- Command:
abacus2J.py - Key Step: Set
outmaths2 1inINPUT. - See: [Workflows > Abacus](references/workflows.md#3-abacus-workflow)
4. Non-Collinear / Anisotropy
- Option A: Full non-collinear DFT +
wann2J.py --spinor. - Option B: "Rotate and Merge" using
TB2Jrotate.py(generate structures) -> DFT ->TB2Jmerge.py(combine results). - See: [Workflows > Non-Collinear](references/workflows.md#4-non-collinear--spin-orbit-coupling-soc)
Troubleshooting / FAQ
- Results contradict experiment?
Check [Conventions](references/conventions.md). Are you comparing $J$ vs $2J$? Verify the Fermi Energy (--efermi) matches the DFT calculation exactly. * Is the system metallic? Try increasing K-mesh or adjusting --nz.
- Wannier functions not localized?
Check wannier90.wout for spreads. Adjust dis_win (outer window) to include all relevant bands. * Check projections.
- "Orbitals not found" error?
Ensure --elements matches the atoms in the structure file. Check if exclude_orbs is needed for semi-core states.