> 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/matpedia-2d.md).

# 2DMatpedia in Duaer

In Duaer: Computed two-dimensional materials in 2DMatpedia by formula or elements, with band gap and chemical system. One successful search uses 1 credit.
## What you get

Duaer 2DMatpedia searches an open database of single-layer (2D) materials obtained by exfoliating layered bulk crystals and by substitution, with DFT band gaps.

Pick Duaer Data → 2DMatpedia in the node creator, or open the [data market](/getting-started/data-market.md). Related: [Materials Cloud MC3D](/getting-started/materials-cloud.md), [JARVIS-DFT](/getting-started/jarvis.md).

## When to use it

- Find monolayer candidates such as MoS2 or graphene analogues.
- Screen 2D materials by band gap for electronics.

## When not to use it

- Bulk 3D crystals. Use [Materials Project](/getting-started/materials-project.md).
- Experimental structures. Use [Crystal structures (COD)](/getting-started/cod.md).

## Search on the canvas

1. Open the node creator and pick Duaer Data → 2DMatpedia.
2. Fill Formula (such as MoS2) or Elements (such as Mo,S).
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/matpedia-2d?formula=MoS2
- 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-matpedia-2d
description: >-
  Duaer 2DMatpedia. Computed two-dimensional materials in 2DMatpedia by formula or elements, with band gap and chemical system.
  One successful search uses 1 Duaer credit.
---

# Duaer 2DMatpedia

Duaer 2DMatpedia searches an open database of single-layer (2D) materials obtained by exfoliating layered bulk crystals and by substitution, with DFT band gaps.

## When to use

- Find monolayer candidates such as MoS2 or graphene analogues.
- Screen 2D materials by band gap for electronics.

## When not to use

- Bulk 3D crystals. Use https://skills.duaer.com/materials-project.md.
- Experimental structures. Use https://skills.duaer.com/cod.md.

## Call

`GET https://api.duaer.com/v1/data/matpedia-2d?formula=MoS2`

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 MoS2. Matches the reduced formula.
- `elements` — Optional. Materials that contain all of these, such as Mo,S.
- `limit` — Optional. Rows to return, from 1 to 20. Default 10.

## Examples

- `GET https://api.duaer.com/v1/data/matpedia-2d?formula=MoS2` — MoS2 monolayers with band gaps.
- `GET https://api.duaer.com/v1/data/matpedia-2d?elements=W,Se&limit=5` — tungsten selenide layers.

## 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.
- `bandGapEv` — DFT band gap in eV.
- `chemicalSystem` — elements joined by dashes, such as Mo-S.

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/jarvis.md — Duaer JARVIS-DFT

```
## Questions

### How many credits does a 2DMatpedia search use in Duaer?

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

### Does Duaer 2DMatpedia hold only 2D materials?

Yes. Duaer 2DMatpedia holds single-layer materials from exfoliating layered bulk crystals and from substitution.

## Related

- [Materials Cloud MC3D in Duaer](https://doc.duaer.com/getting-started/materials-cloud.md)
- [JARVIS-DFT in Duaer](https://doc.duaer.com/getting-started/jarvis.md)