The structures and nonlinear optical responses of Li/Na doped adamantane: A density functional study

On the basis of adamantane, adamantane-Lin (Ad-Li, n = 1-4) and adamantane-Nan (Ad-Na, n = 1-4) were theoretically constructed, for the first time, by Li/Na atom substituting the H atom of adamantane. Eight stable structures of adamantane-Lin (Ad-Li, n = 1-4) and adamantane-Nan (Ad-Na, n = 1-4) are obtained at B3LYP/6-31G(d) level. As Li atoms substituting the edge H atoms of adamantane, first hyperpolarizability of adamantane-Lin decrease with increasing number Li atoms. However, as Na atoms substituting the edge H atoms of adamantane, first hyperpolarizability of adamantane-Nan show an opposite trend and change in the order of Ad-Na1a < Ad-Na2b < Ad-Na3b < Ad-Na4. Among these structure, Ad-Na4 possessed the largest first hyperpolarizability up to 243980 au, which can be attributed to low excitation energies. Furthermore, Ad-Na4 exhibit deep-ultraviolet transparency, which is of great importance in practical applications. We hope that this study could provide an effective method for designing novel nonlinear optical materials.