Development of highly efficient nonlinear optical materials based on alkali and superalkali metals-doped Li12F12 nanocages for advanced electro-optic applications

Nonlinear optical (NLO) materials have gained popularity in the research world due to their numerous applications including optoelectronics, biosensors, lasers, and photonics. In this research, the theoretical study of Li 12 F 12 nanocage doped with alkali and superalkali metal atoms is examined for the first time. DFT calculations are used to explore the electronics, stability, geometric, and nonlinear properties. The stability of designed isomers is predicted by the negative interaction energy values, with an isomer of Li 3 O@ Li 12 F 12 nanocage exhibiting the higher interaction energy ( E b ) of − 49.46 kcal/mol. Doping Li 12 F 12 nanocage with alkali (A) and superalkali (SA) decreased the HOMO–LUMO band gap. For doped isomers, a reduction in the energy gap up to 0.88 eV has been observed for K 3 O@ Li 12 F 12 nanocage which improves the NLO behavior. The maximum first hyperpolarizability value of designed isomers is 4.99 × 10 5 au (VII-K 3 O). NBO and DOS spectra are used to evaluate the charge transfer, the contribution of various parts, and their interactions. NCI analysis is used to perform different types of interactions between Li 12 F 12 nanocage and alkali (Li, Na, K)-superalkali (Li 3 O, Li 4 N, K 3 O, Na 3 O). According to the TD-DFT calculations, complexes have λ max in the near IR and visible region. The QTAIM analysis revealed weak covalent interactions except Na 3 O and Li 4 N complexes. This research may provide a path for the development of stable Li 12 F 12 nanocage isomers, which will serve as essential building blocks for highly effective NLO materials. Graphical Abstract