cryspglib

A pure-Rust port of spglib (2.x) with zero external dependencies, ported entirely with the assistance of AI (DeepSeek-V4-Pro, driven by Claude Code).

Disclaimer: cryspglib is not intended to replace or compete with spglib. It exists to give Rust projects a zero-dependency, pure-Rust alternative that compiles without a C toolchain. It will continue to track upstream spglib as both evolve.

Background

spglib is a widely-used C library in crystallography for identifying space groups, symmetry operations, and standardizing crystal cells. cryspglib is a line-by-line Rust port that preserves the same algorithms and data pipeline as the original C implementation.

Starting from the C source, the AI-assisted porting effort delivered:

• 30+ modules ported from C to Rust (~15,000 lines of code)
• Automatic conversion of the 530 Hall symbol database and 1,651 magnetic space group (UNI) entries
• Complete identification pipelines for both non-magnetic space groups (230) and magnetic space groups (1,651 UNI numbers)
• Space group search, primitive cell reduction, Bravais lattice classification, Wyckoff position refinement, and more
• 70 unit tests + 1 doc test, covering cubic, hexagonal, tetragonal, monoclinic systems and multiple magnetic structures

Features

Non-magnetic space group identification

• Lattice + positions + types → space group (1–230), Hall symbol, international symbol
• Primitive cell finding (spg_find_primitive)
• Cell standardization (spg_standardize_cell)
• Wyckoff position refinement (spg_refine_cell)
• Delaunay / Niggli lattice reduction
• k-point grid generation (Monkhorst-Pack)

Magnetic space group identification

• POSCAR-style input (lattice + positions + types + magnetic moments) → non-magnetic space group + magnetic space group (BNS) + symmetry operations
• Supports Type-1 (ordinary), Type-2 (grey), Type-3 (black-white / anti-rotation), Type-4 (anti-translation)
• Atomic magnetic moments treated as axial vectors (is_axial=true), with correct transformation under spatial inversion

Verified physical systems

Usage

use cryspglib::spg_get_magnetic_dataset;

// BCC AFM [111]: Fe at [0,0,0] and [0.5,0.5,0.5], opposite spins along [111]
let lattice = [[1.0, 0.0, 0.0], [0.0, 1.0, 0.0], [0.0, 0.0, 1.0]];
let positions = [[0.0, 0.0, 0.0], [0.5, 0.5, 0.5]];
let types = [26, 26];
let n = (3.0_f64).sqrt();
let moments = [[1.0/n, 1.0/n, 1.0/n], [-1.0/n, -1.0/n, -1.0/n]];

let result = spg_get_magnetic_dataset(&lattice, &positions, &types, Some(&moments), 1e-5);
// → SpglibMagneticSymmetry {
//     spacegroup_number: 229 (Im-3m),
//     uni_number: 1331,
//     bns_number: "166.101",
//     magnetic_type: BlackWhite (Type-3),
//     num_operations: 24,
//     ...
//   }

Key API

Build

rustup default nightly  # requires nightly Rust (edition 2024)
cargo build
cargo test              # 70 unit tests + 1 doc test

Relationship to upstream spglib

• cryspglib is not a fork or a replacement — it is a companion port that aims to make spglib's functionality available to the Rust ecosystem without requiring a C compiler or FFI bindings
• Algorithms and databases are kept identical to spglib 2.x and will track upstream updates
• Naming conventions preserve the spg_ prefix with snake_case variants for easy migration
• Rust type safety: Option<T> replaces NULL returns, Vec replaces malloc/free, automatic memory management

Acknowledgments

~95% of the code in this project was generated by DeepSeek-V4-Pro via Claude Code. The porting process involved approximately 50+ conversations and hundreds of iterative corrections, with the AI handling everything from line-by-line translation to logic debugging to test authoring.

License

BSD-3-Clause (inherited from spglib)