# Crystallography API > Crystal structures as an API — powered by the Crystallography Open Database (COD), the open, public-domain collection of over 500,000 crystal structures of organic, inorganic, metal-organic compounds and minerals. Search the database by chemical formula (any standard casing — TiO2, Al2O3, H2O — is normalised automatically) or by free text over mineral names, titles and comments, then look up any structure to get its full crystallographic data: chemical and cell formula, space group (Hermann-Mauguin and Hall), the complete unit cell (a, b, c, alpha, beta, gamma and volume), the source publication (title, authors, journal, year, DOI) and a link to the CIF file. From quartz, calcite and diamond to anatase, corundum and diopside, it is ideal for materials science, solid-state chemistry, mineralogy, crystallography teaching and research tooling. This is a crystal-structure & materials database — distinct from molecule-property (chemistry / PubChem) and protein-structure (PDB) databases. Open data from the Crystallography Open Database (CC0 / public domain). ## Authentication All requests require your oanor API key in the `x-oanor-key` header. Get one at https://www.oanor.com/developer/keys. ```bash curl -H "x-oanor-key: oanor_live_…" "https://api.oanor.com/cod-api/..." ``` ## Pricing - **Free** (Free) — 2,200 calls/Mo, 2 req/s - **Starter** ($7/Mo) — 52,000 calls/Mo, 8 req/s - **Pro** ($22/Mo) — 240,000 calls/Mo, 20 req/s - **Mega** ($59/Mo) — 880,000 calls/Mo, 50 req/s ## Endpoints ### Crystallography #### `GET /v1/search` — Search crystal structures by formula or text **Parameters:** - `formula` (query, optional, string) — Chemical formula, any casing (TiO2, Al2O3, H2O) Example: `TiO2` - `text` (query, optional, string) — Free-text search over minerals, titles and comments - `limit` (query, optional, string) — Max results (1-100, default 25) **Example:** ```bash curl -H "x-oanor-key: $KEY" \ "https://api.oanor.com/cod-api/v1/search?formula=TiO2" ``` **Response:** ```json { "data": { "mode": "formula", "count": 25, "query": "O2 Ti", "total": 39, "structures": [ { "url": "https://www.crystallography.net/cod/1010942.html", "year": 1924, "title": "Zur Kristallstruktur von Anastas und Rutil. (II. Teil. Die Anastasstruktur).", "cod_id": "1010942", "formula": "O2 Ti", "mineral": "Anatase", "space_group": "I 41/a m d :1" }, { "url": "https://www.crystallography.net/cod/1526931.html", "year": 2000, "title": "Rietveld analysis of electron powder diffraction data from nanocrystalline anatase, Ti O2", "cod_id": "1526931", "formula": "O2 Ti", "mineral": null, "space_group": "I 41/a m d :2" }, { "url": "https://www.crystallography.net/cod/1528778.html", "year": 2006, "title": "Structure of beta - Ti O2", "cod_id": "1528778", "formula": "O2 Ti", "mineral": null, "space_group": "C 1 2/m 1" }, { "url": "https://www.crystallography.net/cod/1530026.html", "year": 1988, "title": "Ti O2-II. Ambient pressure and structure refinement", "cod_id": " …(truncated, see openapi.json for full schema) ``` #### `GET /v1/structure` — A crystal structure: cell, space group, citation **Parameters:** - `id` (query, optional, string) — A COD id (from /v1/search) Example: `2100348` **Example:** ```bash curl -H "x-oanor-key: $KEY" \ "https://api.oanor.com/cod-api/v1/structure?id=2100348" ``` **Response:** ```json { "data": { "structure": { "doi": "10.1107/S010876810503747X", "url": "https://www.crystallography.net/cod/2100348.html", "cell": { "a": 7.287, "b": 9.2, "c": 6.688, "beta": 90, "alpha": 90, "gamma": 90, "volume": 448.4 }, "year": 2006, "title": "Pressure-frozen benzene I revisited", "cod_id": "2100348", "authors": "Budzianowski, Armand; Katrusiak, Andrzej", "cif_url": "https://www.crystallography.net/cod/2100348.cif", "formula": "C6 H6", "journal": "Acta Crystallographica Section B", "mineral": null, "space_group": "P b c a", "cell_formula": "C24 H24", "space_group_hall": "-P 2ac 2ab" } }, "meta": { "timestamp": "2026-06-01T16:23:15.049Z", "request_id": "dee10794-9954-4650-9f50-7968f026293c" }, "status": "ok", "message": "Structure retrieved", "success": true } ``` ### Meta #### `GET /v1/meta` — Endpoint catalogue & notes **Example:** ```bash curl -H "x-oanor-key: $KEY" \ "https://api.oanor.com/cod-api/v1/meta" ``` **Response:** ```json { "data": { "note": "COD (the Crystallography Open Database) is the open, public-domain collection of crystal structures of organic, inorganic, metal-organic compounds and minerals — over 500,000 entries, each with unit-cell parameters, a space group, a chemical formula and the publication it came from. /v1/search?formula=TiO2 = find structures by chemical formula (any standard casing — TiO2, Al2O3, H2O — is normalised to COD's alphabetical form), or /v1/search?text=quartz = free-text search over mineral names, titles and comments; both return each match's COD id (e.g. 2100348), formula, mineral, space group and year. /v1/structure?id=2100348 = a single structure's crystallographic data — chemical and cell formula, space group (Hermann-Mauguin and Hall), full unit cell (a, b, c, alpha, beta, gamma and volume), the source publication (title, authors, journal, year, DOI) and links to the CIF file. Get a COD id from /v1/search. Data from the Crystallography Open Database (CC0 / public domain). A crystal-structure & materials database — distinct from molecule-property (chemistry/PubChem), protein-structure (PDB) and sequence databases. Ideal for materials science, solid-state chemistry, mineralogy and education.", "source": "Crystallography Open Database (crystallography.net)", "endpoints": [ "/v1/search", "/v1/structure", "/v1/meta" ] }, "meta": { "timestamp": "2026-06-01T16:23:15.1 …(truncated, see openapi.json for full schema) ``` --- Marketplace page: https://www.oanor.com/api/cod-api OpenAPI spec: https://www.oanor.com/api/cod-api/openapi.json