A Density Functional Theory Study on Nonlinear Optical Properties of Double Cage Excess Electron Compounds: Theoretically Design M[Cu(Ag)@(NH 3 ) n ](M = Be, Mg and Ca; n = 1–3)

In this work, we investigated the nonlinear optical (NLO) properties of excess electron electride molecules of M[Cu(Ag)@(NH 3 ) n ](M = Be, Mg and Ca; n  = 1–3) using density functional theory (DFT). This electride molecules consist of an alkaline‐earth (Be, Mg and Ca) together with transition metal (Cu and Ag) doped in NH 3 cluster. The natural population analysis of charge and their highest occupied molecular orbital suggests that the M[Cu(Ag)@(NH 3 ) n ] compound has excess electron like alkaline‐earth metal form double cage electrides molecules, which exhibit a large static first hyperpolarizability ( β 0 e ) (electron contribution part) and one of which owns a peak value ofβ 0 e216,938 (a.u.) for Be[Ag@(NH 3 ) 2 ] and vibrational harmonic first hyperpolarizability ( β z z z nr) (nuclear contribution part) values and the ratio ofβ z z z nr/ β z z z e , namely, η values from 0.02 for Be[Ag@(NH 3 )] to 0.757 for Mg[Ag@(NH 3 ) 3 ]. The electron density contribution in different regions onβ z z z evalues mainly come from alkaline‐earth and transition metal atoms by first hyperpolarizability density analysis, and also explains the reason whyβ z z z evalues are positive and negative. Moreover, the frequency‐dependent values β (−2 ω,ω,ω ) are also estimated to make a comparison with experimental measures. © 2018 Wiley Periodicals, Inc.