Re-examining the giant magnetization density in α′′-Fe₁₆N₂ with the SCAN +U formalism

An in-depth investigation of the magnetic ground state of α′′-Fe₁₆N₂ within the frame work of the density functional theory (DFT) is carried out. The exchange-correlation effects are treated using a variety of schemes, including the local-spin-density approximation, the generalized-gradient approximation, and the Strongly-Constrained-and-Appropriately-Normed (SCAN) scheme. The effects of adding an on-site interaction parameter U on the Fe sites is tested and delineated. Among all the schemes considered, only SCAN + U is found to capture the surprisingly large magnetization density in α′′-Fe₁₆N₂ that has been observed experimentally. Our study shows how the combination of SCAN and different self-interaction corrections applied on the system through the parameter U can reproduce both the correct equilibrium volume and the giant magnetization density of α′′-Fe₁₆N₂.