A Density Functional Theory Study on Nonlinear Optical Properties of Double Cage Excess Electron Compounds: Theoretically Design M[Cu(Ag)@(NH3)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)@(NH3)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 NH3 cluster. The natural population analysis of charge and their highest occupied molecular orbital suggests that the M[Cu(Ag)@(NH3)n] compound has excess electron like alkaline‐earth metal form double cage electrides molecules, which exhibit a large static first hyperpolarizability ( β0e ) (electron contribution part) and one of which owns a peak value of β0e 216,938 (a.u.) for Be[Ag@(NH3)2] and vibrational harmonic first hyperpolarizability ( βzzznr ) (nuclear contribution part) values and the ratio of βzzznr / βzzze , namely, η values from 0.02 for Be[Ag@(NH3)] to 0.757 for Mg[Ag@(NH3)3]. The electron density contribution in different regions on βzzze values mainly come from alkaline‐earth and transition metal atoms by first hyperpolarizability density analysis, and also explains the reason why βzzze values are positive and negative. Moreover, the frequency‐dependent values β(−2ω,ω,ω) are also estimated to make a comparison with experimental measures. © 2018 Wiley Periodicals, Inc.