In this report, we have used the DFT + U + V approach, an extension of the DFT + U approach that takes into account both on-site and intersite interactions, to simulate structural, magnetic, and electronic properties together with the Fe and O K-edge XAS spectra of Fe₃O₄ above the Verwey temperature (T_v). Moreover, we compared the simulated XAS spectra with experimental XAS data. We examined both orthogonalized and nonorthogonalized atomic orbital projectors and compared DFT + U + V to DFT, DFT + U, and HSE as a hybrid functional. It is noteworthy that, despite the widespread use of the same Hubbard U value for Fe_oct and Fe_tet at the DFT + U level in the literature, the HP code identified two distinct values for them using the Hubbard approaches (DFT + U and DFT + U + V). The resulting Hubbard U and V parameters are strongly dependent on the chosen orbital projectors. This study demonstrates how DFT + U + V can improve the structural, magnetic, and electronic properties of Fe₃O₄ compared to approximate DFT and DFT + U. In this context, DFT + U + V supports the half-metallic character of the bulk crystal Fe₃O₄ above T_v, since the Fermi level is found in the t_2g band with a Fe_oct down-spin. Thus, the observations in the current study emphasize the significance of intersite interactions in the theoretical analysis of Fe₃O₄ above the T_v.

We report the comparative study of the electrochemical and photoluminescent properties of two Ir(III) complexes described as [Ir(F₂ppy)₂(N^N)][PF₆], where the F₂ppy ligand is 2-(2,4-difluorophenyl)pyridine and the N^N ligands are pyrazino[2,3-f][1,10]phenanthroline (ppl) and pyrazino[2,3-f][4,7]phenanthroline (ppz). The complexes were used for the fabrication of light-emitting electrochemical cells (LECs). The structures of the complexes have been corroborated by X-ray crystallography. Theoretical calculations were performed to understand the photophysical behavior of the complexes. Both in solution and solid state, the photoluminescence spectra shows that emission is significantly red-shifted in the [Ir(F₂ppy)₂(ppz)][PF₆] complex compared with the [Ir(F₂ppy)₂(ppl)][PF₆] complex. Besides, the [Ir(F₂ppy)₂(ppl)][PF₆] complex exhibits a higher quantum yield and a longer excited state lifetime than the [Ir(F₂ppy)₂(ppz)][PF₆] complex; therefore, in the last case non-radiative decay is predominant due to the stabilization of LUMO orbital (energy gap law). In the fabrication of LEC devices with the [Ir(F₂ppy)₂(ppl)][PF₆] complex, light emission was obtained with a maximum value of luminance equal to 177 cd m⁻², while in the case of the [Ir(F₂ppy)₂(ppz)][PF₆] complex, no luminance was observed. According to the photophysical data, the performance in LEC devices could be explained by the different position of the nitrogens in the ppl and ppz structural isomers, electronically affecting the complex, and therefore its properties. In addition, from the crystallographic analysis it is possible to note that the [Ir(F₂ppy)₂(ppz)][PF₆] complex shows enhanced intermolecular and intramolecular interactions compared with [Ir(F₂ppy)₂(ppl)][PF₆], and consequently a higher ordering of the molecules in the complex with ppz ligand can be expected. This higher order could favour the quenching processes, and consequently enhance the non-radiative deactivation.