FINDSYM: Crystal Structure Symmetry Detection

FINDSYM is a Python package for detecting and analyzing crystal structure symmetries. It provides tools to identify space groups, point groups, and Wyckoff positions in crystalline materials.

Features

• Space Group Detection: Automatically identifies the space group of crystal structures
• Point Group Analysis: Determines the point group symmetries
• Wyckoff Position Assignment: Assigns atoms to their corresponding Wyckoff positions
• Primitive Cell Finding: Converts structures to their primitive cells
• 3D Visualization: Interactive visualization of crystal structures (optional)
• Multiple File Formats: Supports CIF, POSCAR, XYZ, and other common structure formats

Installation

From PyPI (recommended)

pip install findsym

With visualization support

pip install findsym[visualization]

From source

git clone https://github.com/AniruthAnanth/findsympy.git
cd findsym
pip install -e .

Dependencies

• numpy >= 1.18.0
• ase >= 3.20.0 (Atomic Simulation Environment)
• spglib >= 1.16.0 (Space group library)
• matplotlib >= 3.3.0 (optional, for visualization)

Quick Start

Command Line Usage

# Basic symmetry analysis
findsym structure.cif

# With custom tolerance
findsym structure.cif --tolerance 1e-4

# With 3D visualization
findsym structure.cif --visualize

Python API

from findsym import findsym

# Analyze a crystal structure
result = findsym("SrTiO3.cif", tolerance=1e-3, visualize=True)

print(f"Space group number: {result['number']}")
print(f"Point group: {result['point group']}")

Examples

Analyzing SrTiO3

import findsym

# Load and analyze SrTiO3 structure
result = findsym.findsym("SrTiO3_mp-4651_primitive.cif")

# Output will show:
# - Space group information
# - Standardized lattice parameters
# - Wyckoff positions for each atom
# - Symmetry operations

Batch Processing

import glob
from findsym import findsym

# Process multiple structures
for cif_file in glob.glob("*.cif"):
    print(f"Processing {cif_file}...")
    result = findsym(cif_file)
    print(f"Space group: {result['number']}")

Output Information

FINDSYM provides detailed symmetry information including:

• Space Group: International symbol and number
• Point Group: Point group symbol
• Lattice Parameters: Standardized unit cell
• Wyckoff Positions: Site symmetries for each atom
• Symmetry Operations: Complete set of symmetry transformations
• Equivalent Atoms: Grouping of symmetrically equivalent atoms

Supported File Formats

• CIF (Crystallographic Information File)
• POSCAR/CONTCAR (VASP)
• XYZ
• PDB
• And many others supported by ASE

Visualization

When using the --visualize flag or visualize=True parameter, FINDSYM creates an interactive 3D plot showing:

• Crystal structure with atoms colored by element
• Unit cell boundaries
• Proper atomic radii
• Structure information overlay

Advanced Usage

Custom Tolerance

# For high-precision structures
result = findsym("precise_structure.cif", tolerance=1e-5)

# For experimental/noisy data
result = findsym("experimental_structure.cif", tolerance=1e-2)

Programmatic Access

from findsym.core import (
    parse_input,
    find_primitive_cell,
    identify_point_group,
    match_to_standard_space_group
)

# Load structure
structure = parse_input("structure.cif")

# Find primitive cell
primitive = find_primitive_cell(structure)

# Get space group
dataset = match_to_standard_space_group(primitive, tolerance=1e-3)
print(f"Space group: {dataset['international']}")

Contributing

Contributions are welcome! Please feel free to submit a Pull Request. For major changes, please open an issue first to discuss what you would like to change.

License

This project is licensed under the MIT License - see the LICENSE file for details.

Acknowledgments

• Inspired by the original FINDSYM from BYU's Isotropy Software Suite
• Built on top of spglib for symmetry operations
• Uses ASE for structure handling
• Visualization powered by matplotlib