A theoretical study of alkaline-earthides Li(NH3)4M (M = Be, Mg, Ca) with large first hyperpolarizability.

With the aid of ab initio calculations at the MP2 level of theory, a novel type of alkaline-earthides, namely Li(NH3)4M (M = Be, Mg, Ca), has been theoretically designed and investigated. These compounds possess a similar geometric structure, in which the alkali-metal cation Li+ lies near the center of the cagelike (NH3)4 complexant and the alkaline-earth anion M- is located outside. All the proposed alkaline-earthides exhibit extremely large static first hyperpolarizability (β0) up to 8.01 × 106 au, indicating that they can be considered as novel NLO molecules with high performance. The calculated results reveal that the alkaline-earth atom is more suitable to serve as excess electron acceptor in excess electron compounds for increasing the β0 value. We hope that our study can attract more research interest in alkaline-earthides and further experimental research.