materials-project

Research

Query the Materials Project API v3 for crystal structures, band gaps, formation energies, and thermodynamic stability of 150k+ inorganic materials. Use when: (1) searching materials by chemical formula, (2) looking up material properties by MP ID, (3) filtering materials by band gap, energy, or density, (4) finding stable phases for a composition. NOT for: organic molecules (use pubchem-compound), proteins (use uniprot-protein), drug compounds (use chembl-drug).

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Source SKILL.md: https://github.com/beita6969/ScienceClaw/blob/HEAD/skills/materials-project/SKILL.md

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Materials Project API

Search and retrieve computed materials data from the Materials Project database (v3 API). Covers 150k+ inorganic crystalline materials with DFT-computed properties.

Authentication

All requests require the X-API-KEY header set to your Materials Project API key. Store it in the MP_API_KEY environment variable.

export MP_API_KEY="your_api_key_here"

API Base URL

https://api.materialsproject.org/v3

Search by Chemical Formula

curl -s -H "X-API-KEY: $MP_API_KEY" \
  "https://api.materialsproject.org/v3/materials/summary/?formula=Fe2O3&_fields=material_id,formula_pretty,band_gap,formation_energy_per_atom,energy_above_hull,symmetry,density&_limit=10"

Lookup by Material ID

curl -s -H "X-API-KEY: $MP_API_KEY" \
  "https://api.materialsproject.org/v3/materials/summary/?material_ids=mp-149&_fields=material_id,formula_pretty,band_gap,formation_energy_per_atom,energy_above_hull,symmetry,density,structure"

Filter by Band Gap Range

curl -s -H "X-API-KEY: $MP_API_KEY" \
  "https://api.materialsproject.org/v3/materials/summary/?band_gap_min=1.0&band_gap_max=2.0&_fields=material_id,formula_pretty,band_gap,formation_energy_per_atom&_limit=20"

Filter by Thermodynamic Stability

Find materials on or near the convex hull (energy_above_hull close to 0 = stable):

curl -s -H "X-API-KEY: $MP_API_KEY" \
  "https://api.materialsproject.org/v3/materials/summary/?energy_above_hull_max=0.025&elements=Li,Fe,O&_fields=material_id,formula_pretty,energy_above_hull,formation_energy_per_atom&_limit=20"

Filter by Elements

Search for materials containing specific elements:

curl -s -H "X-API-KEY: $MP_API_KEY" \
  "https://api.materialsproject.org/v3/materials/summary/?elements=Si,Ge&_fields=material_id,formula_pretty,band_gap,density&_limit=15"

Key Properties

Property	Description	Unit
`band_gap`	Electronic band gap	eV
`formation_energy_per_atom`	Formation energy per atom from elements	eV/atom
`energy_above_hull`	Energy above convex hull (0 = stable)	eV/atom
`symmetry`	Space group and crystal system	-
`density`	Computed density	g/cm^3
`volume`	Unit cell volume	Angstrom^3
`nsites`	Number of sites in the unit cell	-

Parse Results with Python

curl -s -H "X-API-KEY: $MP_API_KEY" \
  "https://api.materialsproject.org/v3/materials/summary/?formula=TiO2&_fields=material_id,formula_pretty,band_gap,energy_above_hull,density&_limit=10" \
  | python3 -c "
import sys, json
data = json.load(sys.stdin)
for mat in data.get('data', []):
    mid = mat.get('material_id', 'N/A')
    formula = mat.get('formula_pretty', 'N/A')
    bg = mat.get('band_gap', 'N/A')
    ehull = mat.get('energy_above_hull', 'N/A')
    rho = mat.get('density', 'N/A')
    print(f'{mid:12s} {formula:10s} Eg={bg} eV  Ehull={ehull} eV/at  rho={rho} g/cm3')
"

Pagination

Use _limit and _skip for pagination:

# First page
curl -s -H "X-API-KEY: $MP_API_KEY" \
  "https://api.materialsproject.org/v3/materials/summary/?elements=Cu,Zn&_fields=material_id,formula_pretty&_limit=50&_skip=0"

# Second page
curl -s -H "X-API-KEY: $MP_API_KEY" \
  "https://api.materialsproject.org/v3/materials/summary/?elements=Cu,Zn&_fields=material_id,formula_pretty&_limit=50&_skip=50"

Common Query Patterns

Solar cell absorbers: band_gap_min=1.0&band_gap_max=1.8&energy_above_hull_max=0.05
Wide band gap semiconductors: band_gap_min=3.0&band_gap_max=6.0
Metals: band_gap_max=0&is_metal=true
Specific composition: chemsys=Li-Fe-P-O (all materials in that chemical system)

Best Practices

Always specify _fields to limit response size and speed up queries.
Use energy_above_hull_max=0.025 to filter for thermodynamically stable phases.
Check is_deprecated field to avoid outdated entries.
Use chemsys for phase diagram queries across a chemical system.
Rate limit: keep requests under 5 per second to avoid throttling.
For bulk downloads, use the mp-api Python client instead of REST calls.

Data Integrity Rule

NEVER fabricate database results from training data. Every protein ID, gene name, compound property, pathway ID, structure detail, and metadata MUST come from an actual API response in this conversation. If the API returns no results, errors, or partial data, report exactly what happened. Do not "fill in" missing data from memory or make up identifiers.