Study of heteroatom-doped graphene properties using DFT/TD-DFT, QTAIM, NBO, and NCI calculations

This study investigates the impact of doping various heteroatoms (O, S, N, B, and P) within pristine graphene lattice to tailor its structural, electronic, optical, and non-linear optical (NLO) properties through density functional theory (DFT) calculations. Our findings demonstrate that the introduction of these heteroatoms significantly alters the bonding configuration of neighboring atoms in the graphene lattice. The thermodynamic stability of both pristine and doped graphene structures was confirmed by calculating relevant parameters. Doping graphene with O, S, N, B, and P modifies its chemical reactivity. By employing the global molecular reactivity descriptors, O-doped graphene (O-Gr) was identified as the softest compound and S-doped graphene (S-Gr) as the hardest, with respective energy gaps of 1.006 eV and 4.844 eV. Vibrational analysis of the doped graphene systems further corroborated these findings, indicating a disruption of the original pristine graphene structure upon doping. Time-dependent DFT (TD-DFT) analysis revealed that the maximum absorption wavelength is achieved in B-Gr compared to the other investigated systems. Reduced density gradient (RDG-NCI) and quantum theory of atoms in molecules (QTAIM) calculations indicate that all dopant atoms, except P, form covalent bonds with their adjacent carbon atoms. In contrast, P-doping exhibits a partial bonding character. Furthermore, the localized electron density resulting from doping enhances the attractive forces between atoms, a desirable characteristic for promising NLO materials. This observation is consistent with the calculated first-order hyperpolarizability values. These findings suggest that heteroatom doping can effectively modify the properties of pristine graphene for designing novel graphene-based materials.