OPTIMADE Compliant Databases

The OPTIMADE ecosystem looks different in 2026 than it did two years ago. Materials Project finished its r2SCAN migration. Alexandria added millions of new structures. Several smaller providers went offline; new ones came online. Most comparison resources date from 2022–2023. The r2SCAN migration alone changes which MP values you should trust. Follow an old tutorial and you may end up filtering on the wrong thermo endpoint. This directory covers every active OPTIMADE provider as of early 2026: entry counts, functionals, primary data types, compliance level, and the specific workflows each one handles well. ...

Querying the same compound in Materials Project and AFLOW returns different formation energies. Both values are correct. They used different DFT functionals, different pseudopotentials, different reference states. That’s not an error. That’s the thing you need to understand before you build a training set from any of them. Materials Project, AFLOW, OQMD, and JARVIS-DFT each make different computational choices. Here’s what those choices mean for your workflow. What each database actually offers Materials Project ~155,000 inorganic compounds (check materialsproject.org for the current count; it grows regularly). The mp-api Python client is the best-designed API in this space: clean, typed, easy to filter on any property. Calculations use GGA+U for most compounds, with r2SCAN available for a growing subset. ...