Second-order NLO responses of two-cavity inorganic electrides Lin@B20H26 (n = 1, 2): evolutions with increasing excess electron number and various B–B connection sites of B20H26

Abstract

Confining excess electrons in a specific space is an effective strategy to design nonlinear optical (NLO) molecules. The complexants with excess electrons are usually organic compounds, but these compounds are thermally unstable and thus hardly meet the processing requirements of NLO materials. To obtain better thermostability and NLO response molecules, in this work, inorganic compounds of B₂₀H₂₆ isomers containing two cavities were proposed. With the two included cavities, B₂₀H₂₆ can be doped by one or two Li atoms to form electrides of Li@B₂₀H₂₆ and Li₂@B₂₀H₂₆. These electrides show larger NLO responses, with respect to the corresponding undoped complexant of B₂₀H₂₆. Particularly, Li₂@B₂₀H₂₆ has the largest β₀ value of 108 846 a.u. (MP2/6-31+G(d) level) that is 850 times as large as that of corresponding B₂₀H₂₆. Moreover, the change of β₀ values with excess electron number is remarkable for two of the isomers, and differences between the β₀ values among those isomers are also significant owing to various B–B connection sites between the two cavities. Therefore, the present inorganic electrides have not only better performance due to the magnitude of their β₀ values but also better behavior on the molecular-level modulation of NLO.