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Exploring new nonlinear optical materials with excess electron character is extremely important for promoting the application of excess electron compounds in nonlinear optics. Herein, by using density functional theory (DFT) computations, new superalkali-based alkalides Li3O@[12-crown-4]M− are designed as excess electron compounds. QTAIM studies suggest that the complexant interacts with alkali and superalkali clusters through non-covalent interactions. These complexes are thermodynamically stable and their interaction energies range from −33.40 ∼ −44.23 kcal mol-1. The alkalide nature of these compounds is guaranteed by their HOMOs values and NBO charge analysis. Being excess electron compounds, these alkalides shows potential electronic properties. Their HOMO-LUMO gaps ranging from 0.17–0.27 eV. With excellent properties, these complexes show remarkable total hyperpolarizability (βo) response (9.30×104–5.26×106au). Interestingly, the hyperpolarizability response is dependent on the size of alkali metals. The βvec values are quite comparable to total hyperpolarizability at the same level of theory. Furthermore, the hyperpolarizability calculated through two-level model (βtl) values show a trend similar to hyperpolarizability. Additionally, the dynamic hyperpolarizability response for EOPE effects is much pronounced at the dispersion frequency of 532 nm. The second hyperpolarizability response for the dc-Kerr constant is increased up to 2.75 × 1012 au which is much higher than those of previously reported alkalides. Strikingly, the frequency-dependent NLO response shows dependence on alkalide character rather than the size of alkali metal (M). Moreover, the βHRS value is recorded up to 2.16 × 106 au. The significant dipolar contribution to hyperpolarizabilities Φβ(J = 1) are observed for these complexes.

We report geometric, electronic, and NLO properties of designed zintl superatom P7M2 (M = Li, Na, K & Be, Mg, Ca) clusters in which zintl core P7 is substituted with alkali and alkaline earth metals. The studied superatom clusters show excellent thermal and electronic stabilities and their binding energies pe atom range from −21.54 to −95.93 kcal mol−1. The NBO charge analysis reveals excellent charge separation within the clusters, where the charge is transferred from metals to phosphorus atoms. Furthermore, HOMO-LUMO gaps are significantly reduced which illustrates better electronic properties. The calculated first static hyperpolarizability (βo) and second hyperpolarizability (γo) values are up to 282176 × 10−33 and 30869568 × 10−40 esu, respectively. The variational trend and controlling factors for hyperpolarizability (βo) are also estimated by the two-level model study and the values nicely correlate with each other. The highest βtl value of 185423 × 10−33 esu is obtained for P7Mg2 cluster. The obtained significant NLO response for P7Mg2 and P7Ca2 superatom clusters may be attributed to excess electron character. Moreover, to investigate the nonlinearity from the experimental point of view, we carried out hyper Rayleigh scattering (βHRS) measurement where the highest value of 81340.0 × 10−33 esu, is observed for the P7Ca2 superatom cluster. The excellent NLO responses of these zintl superatoms will pave path for further design and synthesis of even better NLO materials.