Strain Effects on the Two-Dimensional Cr₂N MXene: An Ab Initio Study

Structural, electronic, and magnetic properties of two-dimensional Cr₂N MXene under strain were studied. The uniaxial and biaxial strain was considered from -5 to 5%. Phonon dispersion was calculated; imaginary frequency was not found for both kinds of strain. Phonon density of states displays an interesting relation between strain and optical phonon gaps (OPGs), that it implies tunable thermal conductivity. When we apply biaxial tensile strain, the OPG increases; however, this is not appreciable under uniaxial strain. The electronic properties of the dynamically stable systems were investigated by calculating the band structure and electron localization function (ELF) along the (110) plane. The band structure showed a metallic behavior under compressive strain; nevertheless, under tensile strain, the system has a little indirect band gap of 0.16 eV. By analyzing, the ELF interactions between Cr-N are determined to be a weaker covalent bonding Cr₂N under tensile strain. On the other hand, if the Cr atoms reduce or increase their self-distance, the magnetization alignment changes, also the magnetic anisotropy energy displays out-of-plane spin alignment. These properties extend the potential applications of Cr₂N in the spintronic area as long as they can be grown on substrates with high lattice mismatch, conserving their magnetic properties.