> For the complete documentation index, see [llms.txt](https://doc.duaer.com/zh/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/zh/getting-started/alexandria.md).

# 在 Duaer 里查Alexandria

在 Duaer 里：按化学式或元素检索 Alexandria PBE 数据库的数百万 DFT 结构：带隙、形成能与凸包距离。一次成功查询用 1 额度。
## 能拿到什么

Duaer 数据市场里的「Alexandria」：按化学式或元素检索 Alexandria PBE 数据库的数百万 DFT 结构：带隙、形成能与凸包距离。查到结果时用 1 额度，结果交给数字组织的下一个节点。

从节点创建器选 Duaer 数据 → Alexandria，或打开 [数据市场](/zh/getting-started/data-market.md)。相关：[AFLOW](/zh/getting-started/aflow.md)、[Materials Project](/zh/getting-started/materials-project.md)。

## 适合做什么

- 查看某组分是否被预测为稳定（凸包距离接近 0）。
- 查找 Materials Project 之外的计算结构。

## 在画布里检索

1. 打开节点创建器，选 Duaer 数据 → Alexandria。
2. 填 Formula（如 GaAs）或 Elements（如 Ga,As）。
3. Limit 默认 10，最大 20。执行。

查到结果才扣 1 额度；没有结果、输入有误或上游失败都不扣。

## 用 API 调用

- GET https://api.duaer.com/v1/data/alexandria?formula=GaAs
- Authorization: Bearer <Duaer key>

下方是与数据市场「复制技能」相同的英文技能，含参数、示例与返回字段。

## 调用技能（英文）

与数据市场「复制技能」一致。

```
---
name: duaer-alexandria
description: >-
  Duaer Alexandria. Millions of DFT structures in the Alexandria PBE database by formula or elements: band gap, formation energy, and distance to the hull.
  One successful search uses 1 Duaer credit.
---

# Duaer Alexandria

Duaer Alexandria searches the Alexandria PBE database over OPTIMADE. It holds millions of computed structures, including many not found in other databases.

## When to use

- Check whether a composition is predicted stable (hull distance near 0).
- Find computed structures beyond Materials Project.

## When not to use

- Experimental structures. Use https://skills.duaer.com/cod.md.
- Curated properties with elastic data. Use https://skills.duaer.com/jarvis.md.

## Call

`GET https://api.duaer.com/v1/data/alexandria?formula=GaAs`

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

## Examples

- `GET https://api.duaer.com/v1/data/alexandria?formula=GaAs` — GaAs structures with band gap and stability.
- `GET https://api.duaer.com/v1/data/alexandria?elements=Na,S&limit=5` — sodium-sulfur compounds.

## Result

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

- `alexandriaId` — Alexandria id.
- `formula`, `elements`, `sites` — reduced formula, elements, and atoms in the cell.
- `spaceGroupNumber` — symmetry.
- `bandGapEv`, `formationEnergyEvPerAtom`, `energyAboveHullEv` — gap, formation energy, and distance to the convex hull.

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/aflow.md — Duaer AFLOW
- https://skills.duaer.com/materials-project.md — Duaer Materials Project

```
## Questions

### Duaer 的Alexandria检索扣多少额度？

查到结果时扣 1 额度；没有结果或出错不扣。

### Duaer Alexandria 的凸包距离是什么意思？

Duaer Alexandria 的 energyAboveHullEv 越接近 0，结构越可能稳定。

## 相关

- [在 Duaer 里查AFLOW](https://doc.duaer.com/zh/getting-started/aflow.md)
- [在 Duaer 里查 Materials Project](https://doc.duaer.com/zh/getting-started/materials-project.md)