findspingroup 0.15.8

Spin space group (SSG) symmetry analysis toolkit for magnetic materials. Automatically identifies and classifies SSGs, generating symmetry operations, spin Wyckoff positions, and spin Brillouin zones. Designed for integration with first-principles and high-throughput computational workflows.

FindSpinGroup

FindSpinGroup is a Python package and command-line program for identifying oriented spin space group symmetry in magnetic crystal structures.

Given a structure with magnetic moments, FindSpinGroup identifies the oriented spin space group (OSSG), reports the corresponding magnetic space group (MSG), classifies the magnetic phase, and can generate symmetry data for first-principles, high-throughput, and web-application workflows.

The project also powers the public web application:

https://app.findspingroup.com

Installation

pip install findspingroup

FindSpinGroup requires Python 3.11 or newer.

For development from a local checkout:

python -m pip install -e ".[dev]"

Quick Start

Run a compact identification from the command line:

fsg path/to/structure.mcif

This prints a short human-readable summary. Use --show for selected fields or --json for the complete compact JSON payload:

fsg path/to/structure.mcif --show index --show magnetic_phase --show msg_symbol
fsg path/to/structure.mcif --json

Use the Python API when the result will be consumed by another program:

from findspingroup import example_path, find_spin_group_basic

summary = find_spin_group_basic(example_path("0.800_MnTe.mcif"))

print(summary["index"])
print(summary["magnetic_phase"])
print(summary["msg_bns_number"], summary["msg_symbol"])

Expected output:

194.164.1.1.L
AFM(Altermagnet)
63.457 Cmcm

Main Routes

Most users should start with the default CLI command or find_spin_group_basic(...). This route returns the identified OSSG, corresponding MSG, magnetic phase, and compact property flags.

Use the full route, fsg --all or find_spin_group(...), when you need the complete result object, generated artifacts, quasi-2D diagnostics, tensor analysis, or route-specific audit information.

Use fsg -w when you want input-setting symmetry helper files written into the current directory. This route is intended for downstream tools that consume explicit operation files.

The legacy --mode selector is still available for compatibility, but new CLI usage should prefer the default route, --all, and -w.

Main Outputs

Depending on the route, outputs can include:

• identified OSSG index and symbols;
• corresponding MSG identifiers;
• magnetic-phase and spin-splitting classification;
• SSG and MSG operations in named settings;
• SCIF, POSCAR, KPOINTS, and GSPG text artifacts;
• magnetic-site, tensor, quasi-2D, and ferroelectric-switching diagnostics.

Supported Inputs

FindSpinGroup supports:

• magnetic CIF / mCIF files;
• ordinary CIF files when magnetic information is available in supported tags;
• repo-generated SCIF files;
• POSCAR-like files, including POSCAR, CONTCAR, .vasp, .poscar, and explicit ordinary filenames without a CIF/SCIF suffix.

Magnetic moments must be present. For POSCAR-like files, the command-line tool is optimized for VASP working directories and prefers a sibling INCAR MAGMOM when available. Direct Python calls read only the POSCAR content unless INCAR reading is explicitly enabled, which keeps scripted calls reproducible.

When no input file is given, the CLI auto-selects from the current directory in this order: SCIF, mCIF, CIF files with magnetic-moment tags, POSCAR with sibling INCAR MAGMOM, POSCAR with embedded MAGMOM, .vasp / .poscar files with embedded MAGMOM, and finally CONTCAR. Automatic discovery does not scan arbitrary ordinary filenames; pass those POSCAR-like files explicitly.

Quasi-2D Calculations

The default calculation mode is three-dimensional. Quasi-2D analysis is an explicit full-route diagnostic:

fsg --all --calculation-mode quasi2d --vacuum-axis c path/to/slab.mcif

The ordinary 3D symmetry result remains the base result. Quasi-2D data is added only when the quasi-2D calculation mode is requested.

Documentation

The README is only the entry point. Detailed documentation is split into:

• Guide: how to choose a route, run examples, and understand results;
• Reference: exact Python functions, return objects, CLI flags, and output fields;
• Advanced Notes: settings, diagnostics, and validation terminology.

Local source files live under site_docs/ and are published through Read the Docs.

Development

Run focused tests with:

PYTHONPATH=src python -m pytest

For changes that affect symmetry identification, generated cells, route output, or public fields, use focused local regression tests first and then run the agreed project batch validations.

License

FindSpinGroup is licensed under the Apache License, Version 2.0. See LICENSE for details.