Hubbard U

The on-site correction applied to localised d and f electrons in DFT+U.

No model yet

Quantity	What it is	Model
hubbard_u	One value per species, eV	none

One U per species does not fit a single predicted value, and U is not a property of the material alone — the scheme, functional and projector that produced it have to travel with the number. Both are open.

Prior art: Uhrin, Zadoks, Binci, Marzari and Timrov, Machine learning Hubbard parameters with equivariant neural networks, npj Computational Materials 11, 19 (2025). doi:10.1038/s41524-024-01501-5