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Crystal structures (COD) in Duaer

In Duaer: Experimental crystal structures from the Crystallography Open Database by formula, mineral, or words: space group, cell lengths, year, paper, and CIF download. One successful search uses 1 credit.

What you get

Duaer Crystal structures searches the Crystallography Open Database, an open collection of about 500,000 measured structures of minerals, organics, and metal-organics.

Pick Duaer Data → Crystal structures (COD) in the node creator, or open the data market. Related: Materials Project, JARVIS-DFT, compounds.

When to use it

Find measured unit cells and space groups of a mineral or compound.
Get a CIF file to open in a structure viewer or simulation.

When not to use it

Computed properties such as band gaps. Use Materials Project or JARVIS-DFT.
Protein structures. Use structures.

Search on the canvas

Open the node creator and pick Duaer Data → Crystal structures (COD).
Fill Formula (such as SiO2). Optional: Words.
Limit defaults to 10, max 20. Execute.

A search uses 1 credit only when it returns rows. No rows, wrong input, or an upstream failure uses 0.

Call the API

GET https://api.duaer.com/v1/data/cod?formula=SiO2&limit=5
Authorization: Bearer <Duaer key>

The call skill below matches Copy skill in the Duaer data market, with parameters, examples, and result fields.

Call skill

Same text as Copy skill.

---
name: duaer-cod
description: >-
  Duaer Crystal structures (COD). Experimental crystal structures from the Crystallography Open Database by formula, mineral, or words: space group, cell lengths, year, paper, and CIF download.
  One successful search uses 1 Duaer credit.
---

# Duaer Crystal structures (COD)

Duaer Crystal structures searches the Crystallography Open Database, an open collection of about 500,000 measured structures of minerals, organics, and metal-organics.

## When to use

- Find measured unit cells and space groups of a mineral or compound.
- Get a CIF file to open in a structure viewer or simulation.

## When not to use

- Computed properties such as band gaps. Use https://skills.duaer.com/materials-project.md or https://skills.duaer.com/jarvis.md.
- Protein structures. Use https://skills.duaer.com/structures.md.

## Call

`GET https://api.duaer.com/v1/data/cod?formula=SiO2&limit=5`

Header: `Authorization: Bearer <Duaer key>`

Use an account key or a model API key.

Get a Duaer key: https://skills.duaer.com/keys.md

## Parameters

Provide `formula` or `words`.

- `formula` — Formula of one formula unit, such as SiO2 or CaCO3.
- `words` — Optional. Mineral, compound, or author words, such as quartz.
- `limit` — Optional. Rows to return, from 1 to 20. Default 10.

## Examples

- `GET https://api.duaer.com/v1/data/cod?formula=SiO2&limit=5` — silica polymorphs.
- `GET https://api.duaer.com/v1/data/cod?words=perovskite` — entries that mention perovskite.

## Result

The response is `{ "items": [...] }`. Each item has `source`, `title`, `url`, and `summary`, plus:

- `codId`, `cifUrl` — COD id and CIF download link.
- `formula`, `mineral`, `chemicalName` — formula in Hill order and names.
- `spaceGroup`, `spaceGroupNumber` — Hermann–Mauguin symbol and number.
- `a`, `b`, `c`, `alpha`, `beta`, `gamma`, `volume` — cell lengths (Å), angles (°), and volume (Å³).
- `year`, `journal`, `paperTitle`, `doi` — source publication.

Fields without a value are left out.

## Credits

A search that returns at least one row uses 1 credit.
An empty search, a search that finds nothing, or a failed search uses 0.
Wrong input returns 400 with a message and uses 0.
No remaining credits returns 402 and does not search.
A missing key returns 401.

## Related

- https://skills.duaer.com/materials-project.md — Duaer Materials Project
- https://skills.duaer.com/jarvis.md — Duaer JARVIS-DFT
- https://skills.duaer.com/compounds.md

Questions

How many credits does a Crystal structures (COD) search use in Duaer?

One credit when Duaer returns rows. A search with no rows or an error uses 0.

What formula format does Duaer COD accept?

Write it plainly, such as SiO2 or CaCO3, without brackets. Duaer converts it to the COD Hill form.

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