Diminishing Magnetism on Passivation of Ti₄N₃ MXene

MXenes are graphene-like inorganic compounds with a stoichiometric formula of M_n+1X_nT_x, where M is an early transition metal such as titanium (Ti), X is carbon (C), nitrogen (N), or CN, and Tx is the surface termination, such as fluorine (F), oxygen (O), hydroxide (OH), etc. MXenes are layered two-dimensional materials that possess many excellent properties, such as high electrical conductivity, low work function, and high surface-to-volume ratio needed for the current technological advancement. Performing the density functional theory (DFT) based on ab initio quantum mechanical calculations using the Vienna ab initio simulation package (VASP) software program, we studied crystallography, calculated electronic structures, magnetism, and optical properties of Ti₄N₃T_x MXene. Calculations show pristine Ti₄N₃ is ferromagnetic and metallic in nature, with dominant contributions of Ti-3d and N-2p orbitals to the density of states. Surface passivation is usually unavoidable in the synthesis of MXenes. The magnetism is heavily diminished on passivation. Based on the type and concentration of the functionalization group, one may open a small band gap on Ti₄N₃T_x, making it a narrow band gap semiconductor.