in order to understand the MP correction schemes for the formation energies of transition metal oxides I studied the PRB papers of Wang (2006) and Jain (2011), and used the total energies given on the MP pages first for Manganese oxides to reproduce the Advanced Correction value for Mn (-1.68 eV per Mn), which worked out perfectly. So I think I am applying the procedure correctly.
But applying the same method to the iron oxides (FeO, Fe2O3, Fe3O4) did not lead to the correction value of -2.733 eV per Fe which is given on the MP pages, but to -2.27 eV instead. I also found the information online, that Fe3O4 was excluded from the fitting, but this changed the value only to -2.24 eV. I used the experimental standard formation enthalpies as follows: FeO: -272 kJ/mol, Fe2O3: -824.2 kJ/mol, Fe3O4: -1118,4 kJ/mol. These values are taken from wikipedia, and they deviate only within 2 kJ/mol (or 0.02 eV/f.u.) from those given by the NIST Chemistry WebBook (webbook.nist.gov/chemistry) so I think they are reliable.
Using the correction value of -2.27 eV [A] reproduces the experimental values [E] much better as if I take the MP value of -2.733 eV:
FeO: -1.4097 [E], -1.4350 [A], -1.669 [MP]
Fe2O3: -1.7111 [E], -1.6986 [A], -1.886 [MP]
Fe3O4: -1.6596 [E], -1.6353 [A], -1.836 [MP]
All values are given in eV/atom. As said before, I only took MP total energies and applied the procedure of Jain (2011). So my question is whether I did a mistake here or the MP correction value for Fe is wrong, or if anything else was taken into account by MP which is not explained in the stated paper.
A reply would be highly appreciated.