This class implements the GGA/GGA+U mixing scheme, which allows mixing of entries. Entry.parameters must contain a "hubbards" key which is a dict of all non-zero Hubbard U values used in the calculation. For example, if you ran a Fe2O3 calculation with Materials Project parameters, this would look like entry.parameters["hubbards"] = {"Fe": 5.3} If the "hubbards" key is missing, a GGA run is assumed. It should be noted that ComputedEntries assimilated using the pymatgen.apps.borg package and obtained via the MaterialsProject REST interface using the pymatgen.matproj.rest package will automatically have these fields populated.