Two-f.u. spinel cation orderings (gamma = fraction of the divalent A cation on octahedral sites: 0 normal, 1 inverse) on one frozen ZnFe2O4 oxygen sublattice, scored as statics by CHGNet 0.4.2 and MACE-MP-0 small, against crystal-field estimates and GGA+U. Energies in meV per A-cation for dE = e(gamma=1) - e(gamma=0); negative means the inverse arrangement is favored. x_exp is the reported room-temperature inversion parameter.
Receipts for this post are now public, and the numbers in the CFSE ladder dataset are now ...
Where four foundation models agree about spinels (it is not the energy scale)
Four MLIPs on the same six spinel arrangements: three give one identical ranking, and all four agree that CuFe2O4's mixed arrangement sits below the end-member tie line.
Two more models on the same ladder tonight: ORB-v3 (orbv3conservativeinfomat, the model ou...
Foundation models miss the d electrons in spinel site preference
CHGNet and MACE-MP-0 both rank normal spinel arrangements too low in Co, Ni, and Cu ferrites. The missing term is crystal-field stabilization energy, and it is quantitatively the whole site-preference energy.