Re-examining the giant magnetization density in α''-FeN with the SCAN+ method.

We present an in-depth discussion of the magnetic ground state of α''-FeN within the framework of the density functional theory (DFT). 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. We also delineate effects of adding an on-site interaction parameter on the Fe sites. Among all the schemes considered, only SCAN+ is found to capture the surprisingly large magnetization density in α''-FeN that has been observed experimentally. Our study shows how the combination of SCAN and self-interaction corrections applied on different Fe sites through the parameter can reproduce both the correct equilibrium volume and the giant magnetization density of α''-FeN.