The magnetic properties of CrI \(\phantom{0}_3\) monolayers, which were recently measured, have been investigated considering electronic repulsion and localization effects in Cr 3d orbitals. In this study, we propose a DFT approach using Hubbard U corrections to improve accuracy. We compare the valence density-of-states using the HSE06 hybrid functional and the DFT + U approach, which includes U parameters for both Cr 3d and I 5p orbitals. The results of our study indicate that the optimal values for U(Cr \(\phantom{0}_{3d}\) ) and U(I \(\phantom{0}_{5p}\) ) are 3.5 eV and 2.0 eV, respectively. This approach is further applied to improve calculations of electronic and magnetic properties in CrI \(\phantom{0}_3\) monolayers and, more importantly, in bilayers combined with van der Waals functionals. These refinements hold promise for further studies of complex CrI \(\phantom{0}_3\) nanostructures, and may also be of interest for other trihalide few-layer systems.
