Enhanced nonlinear optical responses of doped superalkali metal salts with fluorinated/non-fluorinated planar boron sheets: A theoretical study

The widespread use of nonlinear optical (NLO) materials for contemporary technologies has sparked intense interest in their production with the creation of materials with a continuous endeavor. In this theoretical study, we investigate the NLO responses of doped superalkali (SA) metal salts with planar boron sheets (PBSs). We consider four different substrates (B${}_{10}$, B${}_{10}$F₃, B${}_{16}$, and B${}_{16}$F₃) to create 12 new surfaces ( 1-12) by doping SAs (Li₂F, Li₂OF, Li₂O₂) with them. We optimize the geometries of these surfaces and analyze their frontier molecular orbitals (FMOs) and natural bond orbitals (NBO) to obtain insights into their global chemical reactivity. We also examined their NLO responses ranging as 1.22–$1.67\times 10^{-21}$, 3.39–$7.59\times 10^{-24}$, and $3.5\times 10^{-24}$$$e.s.u. Our results reveal that the doped surfaces exhibit stronger NLO responses compared to the undoped surfaces, and that the strongest NLO response is found in the B${}_{16}$F₃-doped surface. The role of various segments in FMOs is investigated using the TDOS and PDOS spectral analyses. To comprehend the relationship between the SA and the B${}_{10}$F₃ substrates molecule more effectively, non-covalent interaction (NCI) investigation is carried out. Additionally, Time-dependent DFT (TD-DFT) simulations are done for UV–Vis analysis to observe significant redshifts up to 1050$$nm. All the SA-doped surfaces are thermodynamically stable NLO materials with improved NLO responses, so these materials are proposed to be used during the construction of advanced NLO responses.