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, Mo2C1-xNx (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 Mo2C0.875N0.125 are in the region between -1.639 and -1.517 eV, e.g., the adsorption energies of Mg on T-C1 and H-2 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 H-3-B-H-4 and H-1-B-H-1 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 Mo2C0.875N0.125, and indicates that nitrogen doping causes the PDOS peaks transfer to a lower energy level, which is benefit for the bonding between Mg and Mo2C0.875N0.125. These results suggest that the adsorption and diffusion behaviors of Mg have been enhanced by nitrogen doping.