---
title: "Structure relaxation: pick your MLIP"
description: "The relax routes now accept a model parameter for Orb, MACE, or CHGNet."
url: "https://ouro.foundation/posts/mmoderwell/structure-relaxation-pick-your-mlip"
id: "019e54db-b6f8-769a-9fcf-763eb39d00f6"
type: "post"
---

# Structure relaxation: pick your MLIP

Post by @mmoderwell in #materials-science (all) · 2026-05-23

- Asset id: `019e54db-b6f8-769a-9fcf-763eb39d00f6`
- Page: https://ouro.foundation/posts/mmoderwell/structure-relaxation-pick-your-mlip

The structure relaxation routes now let you choose which machine-learning interatomic potential (MLIP) drives the optimization.

When you run [Relax a crystal structure](https://ouro.foundation/routes/mmoderwell/relax-a-crystal-structure) (or the [animation](https://ouro.foundation/routes/mmoderwell/relax-a-crystal-structure-with-animation) / [publish](https://ouro.foundation/routes/mmoderwell/relax-a-crystal-structure-and-publish-results) variants), set the **model** field to pick the calculator:

- **Orb v3** — OMat and MPA variants (conservative and direct, 20- and inf-step)
- **MACE** — MP, MPA, and OMAT foundation models (small / medium / large where applicable)
- **CHGNet**

If you omit `model`, we default to **Orb v3 conservative inf MPA** (`orb-v3-conservative-inf-mpa`), same as before.

Handy when you want to compare potentials on the same CIF, or match the model used elsewhere in a workflow. Feedback welcome if you hit edge cases with a particular structure or model combo.

> Embedded route: [Relax a crystal structure](https://ouro.foundation/routes/mmoderwell/relax-a-crystal-structure)

## Assets in this post

- [Relax a crystal structure](https://ouro.foundation/routes/mmoderwell/relax-a-crystal-structure) (route, id `d040d3b6-faad-40cf-9d7c-999a5c769ed8`)
- [Relax a crystal structure with animation](https://ouro.foundation/routes/mmoderwell/relax-a-crystal-structure-with-animation) (route, id `8659406b-bd11-419a-9ab3-cf3534511b6b`)
- [Relax a crystal structure and publish results](https://ouro.foundation/routes/mmoderwell/relax-a-crystal-structure-and-publish-results) (route, id `fa559e17-9b1f-4604-8bc7-835e129c0107`)