The LDA+U calculated band gap and magnetic moment per Ni site as a function of U and J, within the Lichtenstein approach are demonstrated in Figure 2. The value of U_eff = 5 eV seems sufficient to reproduce the experimental values of band gap E_g = 2.48 eV¹ and magnetic moment per Ni site µ = 2 µ_B,² if we take into account the expected underestimation of the band gap and magnetic moment by the LDA approach. One can of course increase further the U_eff to get the exact experimental values, but it might compromise the accurate representation of the electronic structure of the material.

The calculations were done for both GGA and LDA functionals. GGA is notorious for overestimating bond-lengths and lattice constants, whereas LDA usually performs in an opposite way. We chose to continue the parametrization of the model Hamiltonian with the LDA approach, since it seems to produce more accurate values for the magnetocrystalline anisotropy and the exchange interactions. Such behaviour, is expected due to the highly local superexchange interactions, which are sensitive to the bond lengths among Ni-O-Ni.

References

1. Xu, L. et al. Ilmenite-type semiconductor Ni3TeO6: Preparation, optical property and photo-degradation ability. Mater. Lett. 184, 1–4 (2016).

2. Oh, Y. S. et al. Non-hysteretic colossal magnetoelectricity in a collinear antiferromagnet. Nat Commun 5, 3201 (2014).