Legacy API data

Accessing Legacy Materials Project Structures

Older Materials Project (MP) IDs referenced in the literature and MPContribs entries may not be directly accessible via the new API, even with deprecated=True. Many of these structures can still be retrieved using the new API's tasks endpoint. The legacy API is also still accessible (as of mid-2025), but its use is discouraged for new work.

Recommended: Using the Next-Gen API (mp-api) — Tasks Endpoint

To retrieve structures for legacy MPIDs (including mvc- and old mp- IDs), use the tasks endpoint:

from mp_api.client import MPRester

with MPRester() as mpr:
    tasks = mpr.materials.tasks.search(task_ids=['mvc-13350', 'mvc-16068', 'mvc-13133', 'mp-867303']) # Each item in 'tasks' contains the structure and associated information for task in tasks: print(task.task_id, task.structure)

Note:

• The structure you retrieve may not exactly match the one referenced in older publications.

• The tasks endpoint is preferred and supported for retrieving historical structure data.

Legacy API (not recommended, will cease operation in September 2025)

If you must access the legacy API (e.g., for reproducibility), you can use an older version of pymatgen:

1. Install pymatgen 2022.7.25 (or similar):

   pip install 'pymatgen==2022.7.25'

2. Query legacy structures (requires legacy API key):

   from pymatgen.ext.matproj import MPRester as MPResterLegacy 
   from pymatgen.core import Structure 
   
   LEGACY_API_KEY = "your_legacy_api_key_here"  # 19-character string 
   query = {"formula": "FeO"}  # Or any other valid query 
   with MPResterLegacy(LEGACY_API_KEY) as mpr:
       materials = mpr.query(query, ["material_id", "cif"], mp_decode=False) 
       structures_by_mpid = { doc["material_id"] : Structure.from_str(doc["cif"], fmt="cif") for doc in materials }

Caveats:

• The legacy API is currently being phased out, and will be retired in September 2025

• There is no official support for the legacy API

• Bulk download of the full legacy database is available as of snapshot 28 October, 2022, and older snapshots may be made available (see MP AWS downloads for updates).

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