Stability and Nonlinear Optical Response of Alkalides that Contain a Completely Encapsulated Superalkali Cluster.

Guided by density functional theory (DFT) computations, a new series of superalkali-based alkalides, namely FLi2 (+) (aza222)K(-) , OLi3 (+) (aza222)K(-) , NLi4 (+) (aza222)K(-) , and Li3 (+) (aza222)K(-) were designed with various superalkali clusters embedded into an aza222 cage-complexant. These species possess diverse isomeric structures in which the encapsulated superalkalis preserve their identities and behave as alkali metal atoms. The results show that these novel alkalides possess larger complexation energies and enhanced hyperpolarizabilities (β0 ) compared with alkali-metal-based and previous superalkali-based clusters. Especially, a prominent structural dependence of β0 is observed for these studied compounds. Hence, the geometric factors that affect the nonlinear optical (NLO) response of such alkalides is elucidated in detail in this work. This study not only provides novel candidates for alkalides, it also offers an effective way to enhance the NLO response and stability of alkalides.