pymatgen-core

2026.4.16 verified Fri May 01 auth: no python

Python Materials Genomics (pymatgen) core library for materials analysis, providing object representations for structures, molecules, and crystals. Current version 2026.4.16, released April 2026. Active development with monthly releases, compatible with Python >= 3.11. This package is a refactored subset of the original pymatgen, focusing on core data structures and basic I/O.

pip install pymatgen-core

Common errors

error ImportError: cannot import name 'Structure' from 'pymatgen' (unknown location) ↓

cause pymatgen-core moved core classes to pymatgen.core subpackage.

fix

Use 'from pymatgen.core import Structure' instead.

error ModuleNotFoundError: No module named 'pymatgen.io.vasp' ↓

cause VASP I/O is not part of pymatgen-core; it's in the full pymatgen package.

fix

Install pymatgen (the full package) via 'pip install pymatgen' and import from 'pymatgen.io.vasp'.

error AttributeError: 'Structure' object has no attribute 'get_sorted_structure' ↓

cause Some methods may not be available in pymatgen-core if they were moved to other modules.

fix

Check the pymatgen-core documentation for available methods. Use pymatgen (full) if the method is missing.

Warnings

breaking pymatgen-core is a refactored subset of pymatgen. Many modules (e.g., analysis, io.vasp, electronic_structure) are not included; they remain in the full pymatgen package. Code that imports from pymatgen.core will break if it expects all functionality of pymatgen. ↓

fix Install pymatgen (the full package) if you need advanced features. Use pymatgen-core only for core data structures and basic I/O. Adjust imports to use pymatgen.core subpackage.

gotcha Some classes that were previously at the top-level pymatgen (e.g., Structure, Molecule) are now inside pymatgen.core. Direct imports from pymatgen will fail with ImportError or AttributeError. ↓

fix Change 'from pymatgen import Structure' to 'from pymatgen.core import Structure'.

deprecated The original pymatgen package may eventually be superseded by pymatgen-core. Users should monitor migration guides for future breaking changes. ↓

fix Stay updated with release notes. Consider using pymatgen-core for new projects if you only need core features.

Imports

Structure
wrong
```
from pymatgen import Structure
```
correct
```
from pymatgen.core import Structure
```
In pymatgen-core, core classes are under pymatgen.core, not top-level pymatgen.
Molecule
wrong
```
from pymatgen import Molecule
```
correct
```
from pymatgen.core import Molecule
```
Same as Structure; Molecule moved to pymatgen.core.

Lattice

wrong

from pymatgen import Lattice

correct

from pymatgen.core import Lattice

Lattice is also in pymatgen.core.

Element

wrong

from pymatgen import Element

correct

from pymatgen.core import Element

Element moved to pymatgen.core.

Quickstart

Create a silicon diamond cubic structure using pymatgen-core. Note: import from pymatgen.core, not pymatgen directly.

from pymatgen.core import Structure, Lattice, Element

# Create a simple silicon diamond cubic structure
lattice = Lattice.cubic(5.431)  # lattice constant in Angstrom
species = [Element("Si")] * 8
coords = [
    [0, 0, 0],
    [0.25, 0.25, 0.25],
    [0.5, 0.5, 0],
    [0.5, 0, 0.5],
    [0, 0.5, 0.5],
    [0.75, 0.75, 0.25],
    [0.75, 0.25, 0.75],
    [0.25, 0.75, 0.75]
]
structure = Structure(lattice, species, coords, coords_are_cartesian=False)
print(structure)
print(f"Volume: {structure.volume:.2f} Å³")