> For the complete documentation index, see [llms.txt](https://doc.duaer.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://doc.duaer.com/getting-started/omdb.md).

# Open Materials Database in Duaer

In Duaer: Crystal structures in the Open Materials Database by formula or elements, with cell formula, sites, and periodicity. One successful search uses 1 credit.
## What you get

Duaer Open Materials Database searches the openmaterialsdb.se structure collection over OPTIMADE. It returns standard structure fields only.

Pick Duaer Data → Open Materials Database in the node creator, or open the [data market](/getting-started/data-market.md). Related: [Materials Cloud MC3D](/getting-started/materials-cloud.md), [Crystal structures (COD)](/getting-started/cod.md).

## When to use it

- Cross-check a structure against another open database.
- List structures that contain a set of elements.

## When not to use it

- Band gaps or energies. Use [Materials Project](/getting-started/materials-project.md).
- 2D layers. Use [2DMatpedia](/getting-started/matpedia-2d.md).

## Search on the canvas

1. Open the node creator and pick Duaer Data → Open Materials Database.
2. Fill Formula (such as CaMgO6Si2) or Elements (such as Ca,Mg).
3. 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/omdb?formula=CaMgO6Si2
- 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-omdb
description: >-
  Duaer Open Materials Database. Crystal structures in the Open Materials Database by formula or elements, with cell formula, sites, and periodicity.
  One successful search uses 1 Duaer credit.
---

# Duaer Open Materials Database

Duaer Open Materials Database searches the openmaterialsdb.se structure collection over OPTIMADE. It returns standard structure fields only.

## When to use

- Cross-check a structure against another open database.
- List structures that contain a set of elements.

## When not to use

- Band gaps or energies. Use https://skills.duaer.com/materials-project.md.
- 2D layers. Use https://skills.duaer.com/matpedia-2d.md.

## Call

`GET https://api.duaer.com/v1/data/omdb?formula=CaMgO6Si2`

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 `elements`.

- `formula` — Formula such as CaMgO6Si2. Matches the reduced formula.
- `elements` — Optional. Materials that contain all of these, such as Ca,Mg.
- `limit` — Optional. Rows to return, from 1 to 20. Default 10.

## Examples

- `GET https://api.duaer.com/v1/data/omdb?formula=CaMgO6Si2` — diopside structures.
- `GET https://api.duaer.com/v1/data/omdb?elements=Ca,Mg&limit=5` — structures with calcium and magnesium.

## Result

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

- `structureId` — provider id.
- `formula`, `formulaCell`, `elements`, `sites` — reduced formula, cell formula, elements, and atoms in the cell.
- `periodicDimensions` — 3 for bulk crystals.

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-cloud.md — Duaer Materials Cloud MC3D
- https://skills.duaer.com/cod.md — Duaer Crystal structures (COD)

```
## Questions

### How many credits does a Open Materials Database search use in Duaer?

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

### Which fields does Duaer Open Materials Database return?

Duaer Open Materials Database returns standard OPTIMADE structure fields such as formula, elements, and lattice, with no energies.

## Related

- [Materials Cloud MC3D in Duaer](https://doc.duaer.com/getting-started/materials-cloud.md)
- [Crystal structures (COD) in Duaer](https://doc.duaer.com/getting-started/cod.md)