Electronic and Optical Properties of Antiferromagnetic MnF₂

In recent decades, MnF₂ has received considerable interest due to its simple antiferromagnetic structure and its promising applications in spintronic devices. While the magnetic properties of MnF2 have been extensively characterized experimentally, theoretical approaches have failed to accurately predict its electronic structure. This is evident in the discrepancy between the values predicted by electronic-structure theory, which is less than 7.3 eV, and the measured values of more than 9.9 eV based on reflectance and absorption spectra. Furthermore, no prior computational studies have predicted its optical properties to enlighten this question. We employed DFT with the HSE06 hybrid exchange-correlation functional and applied many-body perturbation theory via GW calculations to compute the electronic structure. Subsequently, we approximated this data using a PBE+<i>U</i> approach and a band-dependent scissor shift to achieve a converged <b>k</b>-point sampling for Bethe-Salpeter calculations of the excitonic optical spectrum. Surprisingly, we find excellent agreement with peak positions and amplitudes of the experimental spectrum across a wide range of photon energies up to 17 eV only after assuming an additional scissor shift of 2.4 eV. To explain additional shift, we analyze the effect of the lattice parameter, the magnetic structure, and different <i>GW</i> methods.