Effect of n-Type Dopant Nitrogen in the Structure and Atomic Charges Distribution of Monolayer Graphene Sheet: A DFT Analysis

Theoretical calculations are very powerful tool in the investigation of energetically most stable electronic structures and partial atomic charges distribution of the multi-atomic systems. Being one of the most important ab initio methods, two-dimensional (2D) periodic boundary condition (PBC) calculations of density functional theory (DFT) model are more specifically applicable while computing structures and properties of solid state multi-electron atomic or molecular systems. Present work is aimed at investigating and analyzing the effect of n-type dopant nitrogen in the ground state electronic structures and partial atomic charges distribution of the 2D monolayer graphene sheet by employing 2D PBC calculations of the DFT. At first, the 2D low energy unit cell structures of N-doped and undoped graphene sheets are produced separately and then confirmed hexagonal, honeycomb-like pattern of the carbon rings in their lattice. Interestingly, no significant distortions to the graphene lattice are observed while doping N atom (graphitic N-doping type). The inhomogeneous partial atomic charges in the terminal and nonterminal carbon atoms as well as a strong charge variation in the N and C atoms bonded to N are predicted by the Mulliken population analysis method. These theoretical achievements are not only important to speculate the most chemically "active-sites" in the N-doped and undoped monolayer graphene sheets, but also to justify increased capacitance of N-doped graphene materials. It is believed that present study would be very useful while functionalizing such 2D solid materials, means while tuning their physicochemical properties.