xtalgen — VASP / Wannier90 / TB2J for Simstack

Capability package for crystal magnetism workflows:

• vasp — VASP run + Wannier90 (write helpers inside run nodes)
• tbj2 — TB2J exchange parameters
• master — end-to-end VASP → Wannier90 → TB2J orchestration

Upstream examples (not vendored): TB2J_examples.

Layout

xtalgen/
pyproject.toml
vasp/ # import vasp
tbj2/ # import tbj2
master/ # import master

Install

uv sync # from this directory# or: uv pip install -e ".[dev]"

Pulls simstackv2.0.1 and TB2J from GitHub. Upstream hard-deps sisl / pypao are excluded for the Wannier path (tool.uv.exclude-dependencies); add --extra siesta when you need Siesta.

VASP and wannier90.x are external binaries — put them on PATH / configure [*.program.vasp] in config.toml.

Examples live upstream (not vendored): https://github.com/mailhexu/TB2J_examples

Inside the simstack-model monorepo:

uv pip install -e "./xtalgen[dev]"

If resolver hits pypao/sisl (those settings apply to uv sync, not always to uv pip), install TB2J separately:

uv pip install -e "./xtalgen[dev]" --no-deps
uv pip install "TB2J @ git+https://github.com/mailhexu/TB2J.git" --no-deps

VASP + Wannier90 nodes

Only run callables are @nodes. Input writing lives in vasp.lib and is invoked inside the run nodes.

Node	Role
vasp_run	Write INCAR/KPOINTS + stage POSCAR/POTCAR, then context.resource_config.run("vasp")
wannier90_run	Write {seed}.win (optional), then run wannier90.x → *_hr.dat, *_centres.xyz
vasp_stage_wannier_for_tb2j	Verify TB2J inputs; parse E-fermi from OUTCAR

Helpers (not nodes): vasp.lib.write_vasp_inputs, vasp.lib.write_wannier90_wins.

Binary / launcher: [<resource>.program.vasp] run_command in config.toml (e.g. vasp_std, srun vasp_ncl). MPI ranks come from parent_parameters.slurm_parameters on the job allocation — not from the input model. Workdir is always cwd.

Typical collinear flow (SrMnO3-style) — use master node vasp_wannier_tb2j (VaspWannierTB2JInput) or the steps individually:

1. vasp_run (VaspJobInput with LWANNIER90; stage .win via extra_files or write later)
2. wannier90_run (channels="wannier90.up wannier90.dn", write_win=True)
3. vasp_stage_wannier_for_tb2j
4. tbj2_wannier_collinear (from tbj2)

SOC / spinor: set collinear=False on the master input (and LSORBIT / vasp_ncl in config), or run seed wannier90 then tbj2_wannier_spinor.

License note: VASP and PAW POTCAR files are proprietary and are not shipped.

TB2J nodes

Node	CLI
tb2j_wannier_collinear	wann2J.py
tb2j_wannier_spinor	wann2J.py --spinor
tb2j_siesta	siesta2J.py
tb2j_rotate	TB2J_rotate.py
tb2j_merge	TB2J_merge.py

Register

uv run create_model_table --dir vasp --dir tbj2 --dir master
uv run create_node_table --dir vasp --dir tbj2 --dir master

Docs: https://tb2j.readthedocs.io/en/latest/ · https://www.vasp.at/