Adsorption and diffusion of magnesium on nitrogen-doped Mo₂C monolayer

The Mg adsorption and diffusion behaviors on nitrogen-doped (N-doped) Mo₂C monolayer have been investigated by the first principles based on density functional theory (DFT). To investigate the effect of nitrogen concentration on adsorption energies, Mo₂C_1-xN_x (x=0.0625, 0.125, 0.1875, and 0.25) with four different nitrogen doping concentrations have been considered in the present work. The results show that N-doped Mo₂C is benefit for Mg adsorption. In particular, when the doping concentration reaches to 14.29%, the adsorption energies of Mg on Mo₂C_0.875N_0.125 are in the region between -1.639 and -1.517 eV, e.g., the adsorption energies of Mg on T_C1 and H₂ sites are -1.639 eV and -1.625 eV, which are decreased by 16.49% and 18.43% as compared with the pristine Mo₂C. The calculations on diffusion behaviors show that the Mg diffusing between two adjacent favored sites via a high-symmetry site along H₃-B-H₄ and H₁-B-H₁ paths possesses the barriers of 0.021 eV and 0.028 eV. Additionally, the partial density of states (PDOS) reveals the interaction between Mg and Mo₂C_0.875N_0.125, and indicates that nitrogen doping causes the PDOS peaks transfer to a lower energy level, which is benefit for the bonding between Mg and Mo₂C_0.875N_0.125. These results suggest that the adsorption and diffusion behaviors of Mg have been enhanced by nitrogen doping.