First theoretical framework of superalkali metals [M3X(M = Li, Na, k; X = O, S, F, N)] doped all-boron B38 nanocluster: A promising class of nonlinear optical materials for optoelectronic applications

Developing highly efficient nonlinear optical (NLO) materials is an area of frontier research. For the first time, all-boron fullerene analogue B38 nanocluster is utilized for creating highly efficient NLO materials. An effective computational design strategy of superalkali metals (Li₃O, Na₃O, K₃O, Li₃S, Na₃S, K₃S, Li₃F, Li₃N) doping is utilized on B38 nanocluster, and sixteen stable isomers (A-P) of M₃X@B38 (M = Li, Na, K; X = O, S, F, N) are amplified for NLO properties. Potential utilization of superalkali metals doped B38 nanocluster for NLO response applications is confirmed through DFT and TD-DFT calculations executed for estimating NLO properties, photophysical features, interaction energies (E_int), vertical ionization energies (VIE), non-covalent interaction (NCI), natural bond orbitals (NBO), frontier molecular orbital (FMO), density of state (DOS) and molecular electrostatic potential (MEP) analysis. The VIE and E_int results indicate that superalkalis@B38 complexes are thermodynamically stable enough and show a strong interaction between B38 and doped superalkalis. Doping of superalkalis on B38 successfully lowers the energy gap from 1.99 (pristine B38) to 0.99 eV (doped B38). A triggering in dipole moment from 0.001924 D to 22.61 D is observed upon doping. NCI and NBO analysis confirmed the successful intermolecular charge transfer among superalkalis and B38. UV–Vis analysis showed that all superalkalis@B38 complexes are sufficiently transparent in the near-infrared (NIR) region. The NLO responses of developed complexes are evaluated by their polarizability and first hyperpolarizability (β_o). Amplification in polarizability value from 413.69 a.u. to 865.60 a.u and in first hyperpolarizability from 0.71 a.u to 4.0 × 10⁵ a.u. is achieved upon superalkalis@B38 doping. An eye-catching and highest NLO response (β_o = 4.0 × 10⁵ a.u) is exhibited by isomer E(K₃O@B38). The NLO response of all studied complexes is also found more significant than the standard prototype molecule. This report provides an efficient superalkali doping technique for creating highly effective future NLO systems and recommends superalkali-doped all-boron fullerene analogue B38 nanoclusters as ideal entrants for future NLO applications.