Confinement of quasi-atomic structures in Ti2N and Ti3N2 MXene electrides

Abstract

Metal carbides, nitrides, or carbonitrides of early transition metals, better known as MXenes, possess notable structural, electrical, and magnetic properties. Analyzing electronic structures by calculating structural stability, band structure, density of states, Bader charge transfer, and work functions utilizing first principle calculations, we revealed that titanium nitride MXenes, namely Ti${}_2$N and Ti${}_3$N${}_2$, have excess anionic electrons in their lattice voids, making them MXene electrides. Bulk Ti${}_3$N${}_2$ has competing antiferromagnetic (AFM) and ferromagnetic (FM) configurations with slightly more stable AFM configuration, while the Ti${}_2$N MXene is nonmagnetic. Although Ti${}_3$N${}_2$ favors AFM configuration with hexagonal crystal systems having $6/mmm$ point group symmetry, Ti${}_3$N${}_2$ does not support altermagnetism. The monolayer of the Ti${}_3$N${}_2$ MXene is a ferromagnetic electride. These unique properties of having non-nuclear interstitial anionic electrons in the electronic structure of titanium nitride MXene have not yet been reported in the literature. Density functional theory calculations show TiN is neither an electride, MXene, or magnetic.