Electronic Supplementary Material (ESI) for Physical Chemistry Chemical Physics. This journal is © the Owner Societies 2018 Repairing the single and double atomic vacancies in the C3N monolayer by CO or NO molecules: a first-principle study Dongwei Ma1,, Jing Zhang1, Yanan Tang2, Zhaoming Fu3,, Zongxian Yang3, and Zhansheng Lu3 1School of Physics, Anyang Normal University, Anyang 455000, China 2College of Physics and Electronic Engineering, Zhengzhou Normal University, Zhengzhou 450044, China 3College of Physics and Materials Science, Henan Normal University, Xinxiang 453007, China Electronic Supporting Information Corresponding author. E-mail: [email protected] (Dongwei Ma). Corresponding author. E-mail: [email protected] (Zhaoming Fu). Fig. S1. (a) The top views of the VC2 and VN2 systems. Band structures for the VC2 and VN2 systems are shown in (b) and (c), respectively, where the black and red lines denote the spin-up and spin-down states, respectively. The Fermi level (Ef) is set to 0 eV. The structural parameters are in Å. Fig. S2. The top (a) and side (b) views of the O-doped C3N monolayer with the lattice C atom replaced by the O atom. Fig. S3. The top (a) and side (b) views of the doped C3N monolayer with two neighboring C atoms replaced by two N atoms. The structural parameters are in Å. Fig. S4. Atomic configurations of the IS, TS and FS along the MEP for the filling process of the first CO molecule into VCC (a) and VCN (b). The energies of the IS, TS and FS are given with respect to the total energy of the IS. The structural parameters are in Å. Fig. S5. Atomic configurations of the IS, TS, and FS along the MEP for the removal process of the extra O atom. (a) CO on the VCC surface and (b) CO on the VCN surface. The relevant structural parameters (in Å) and the energies of the IS, TS, and FS are given, which are respect to the total energy of the IS. Fig. S6. Atomic configurations of the IS, TS, and FS along the MEP for transformation from VN2 to VN. The relevant structural parameters (in Å) and the energies of the IS, TS, and FS are given, which are respect to the total energy of the IS. .