Datasetpublic

materials-toolkits/materials-project

Dataset Materials project (2019 dump) This dataset contains 133420 materials with formation energy per atom. Processed from mp.2019.04.01.json Download Download link: materials-project.tar.gz MD5 checksum c132f3781f32cd17f3a92aa6501b9531 Content Bundled in materials-project.tar.gz. Index (index.json) list of dict: index (int) => index of the structure in data file. id (str) => id of Materials Project. formula (str) => formula. natoms… See the full description on the dataset page: https://huggingface.co/datasets/materials-toolkits/materials-project.

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Dataset

Materials project (2019 dump)

This dataset contains 133420 materials with formation energy per atom.

Processed from mp.2019.04.01.json

Download

Download link: materials-project.tar.gz

MD5 checksum c132f3781f32cd17f3a92aa6501b9531

Content

Bundled in materials-project.tar.gz.

Index (`index.json`)

list of dict:

—index (int) => index of the structure in data file.
—id (str) => id of Materials Project.
—formula (str) => formula.
—natoms (int) => number of atoms.
—energy_pa (float) => formation energy per atom.

Data (`data.hdf5`)

fields:

—structures => a group containing structure information.
—structures/cell (float32) => lattice of the material.
—structures/natoms (int32) => number of atoms.
—structures/energy_pa (float32) => formation energy per atom.
—structures/atoms_ptr (int64) => position of the first atom of the structures in the atoms group.
—atoms => a group containing information about atoms.
—atoms/positions (float32) => the positions of the atoms.
—atoms/atomic_number (uint8) => the atomic number of the atoms.

2026 release (`all.hdf5`)

all.hdf5 is a newer, separate export of the Materials Project, preprocessed with pycrystalgen. It does not replace materials-project.tar.gz above and uses a different layout.

It contains 271,325 structures (6,967,262 atoms, 1 to 444 atoms per structure): every material of the summary collection of database version 2026.09.28, except the 8,834 materials flagged as deprecated. Nothing else is filtered.

Labels

Field	Source column	Meaning
`total_energy`	`energy_per_atom` × `nsites`	total energy of the cell in eV, with the corrections of the Materials Project
`formation_energy_per_atom`	`formation_energy_per_atom`	formation energy in eV/atom
`energy_above_hull`	`energy_above_hull`	energy above the convex hull in eV/atom
`band_gap`	`band_gap`	band gap in eV

Four materials have no labels in the source and are kept with NaN. Material ids are not stored: structures are in the order of the source collection, deprecated materials removed.

Format

Flat concatenated arrays:

Dataset	Shape	Type	Content
`lattice`	(n_struct, 3, 3)	float32	lattice vectors as rows, in angstrom
`num_atoms`	(n_struct,)	int64	number of atoms of each structure
`ptr`	(n_struct,)	int64	index of the first atom of each structure in `x` and `z`
`x`	(n_atoms, 3)	float32	fractional coordinates in [0, 1)
`z`	(n_atoms,)	int64	atomic numbers
`total_energy`, `formation_energy_per_atom`, `energy_above_hull`, `band_gap`	(n_struct,)	float32	labels, NaN when unknown

The lattice is rebuilt from cell lengths and angles, so it is in the standard orientation (first vector along x). The batch array is an artefact of the writer and is not used when reading.

Usage

python

from pycrystalgen.data import HDF5Dataset

dataset = HDF5Dataset.from_hub("materials-toolkits/materials-project", "all.hdf5")
structures = dataset[:32]  # batched Structures

Source, processing and licence

—Source: the public open data bucket of the Materials Project, materialsproject-build/collections/summary/version=2026-09-28/.
—Built with pycrystalgen, scripts/build_materials_project.py: collection to CIF, then CIF to HDF5.
—Every structure was checked against the source: number of atoms, elements, fractional coordinates, lattice and the four labels.

Licence of `all.hdf5`: the license: mit of this repository describes the 2019 files, not this one. In the source, each material carries its own licence label: 154,377 of the structures kept here are labelled BY-C and 116,948 are labelled BY-NC (non-commercial). This file does not record which structure has which label, so treat the whole file as non-commercial unless you check against the source, and refer to the Materials Project for the terms of use.