Theoretical Study On The Origin Of Electride And Alkalide And Their Large Nonlinear Optical Properties

By doping the model complexant N₃H₃ with one or two lithium atoms, the geometrical and electronic structures as well as static electric properties of the resulting Li（N₃H₃）,（N₃H₃）Li′ and Li（N₃H₃）Li′ complexes have been explored using the B3 LYP, BHand HLYP, CAM-B3 LYP and MP2 methods. All the three complexes have large first hyperpolarizabilities（β0）, especially Li（N₃H₃）. Meanwhile, Li（N₃H₃） and Li（N₃H₃）Li′ exhibit electride and alkalide characteristics, respectively. The dependences of electric properties of alkalide Li（N₃H₃）Li′ on the involved alkali atoms and the complexant layer number are revealed by investgating the related M（N₃H₃）Li′ and Li（N₃H₃）M′（M = Na and K）, and Li（N₃H₃）nLi′（n = 2, 3） systems. Note that the β0 value of alkalide M（N₃H₃）M′ increases not only with the increasing atomic number of the M′- anion but also with that of the M+ cation, which is different from the cases reported previously. In addition, the electric properties of the Li（N₃H₃）Li′ alkalide can also be enhanced by increasing the complexant layers. However, it is found that both the complexant-complexant and the complexant-Li′ interactions reduce with the addition of N₃H₃ layers, so stable structures could not be found for larger Li（N₃H₃）nLi′ complexes.