Theoretical research on nonlinear optical properties of sandwich compounds M3-NO3-M'3 (M, M' = Li, Na, K)

Abstract

Six sandwich compounds metal-nonmetal-metal have been designed, which are composed of superalkali metal (Li3, Na3, K3) and superion (NO3–). The compounds were optimized by MP2/6-311g (2D) method to obtain the stable geometry. The analysis of NBO charge shows that in M3-NO3-M'3 the charge of M and M' are about +1, and the charge of NO3– is about −2. Therefore, it is a charge separation system, which can be recorded as M3+–NO32−-M'3+. In this special structure, the superions in the center repel the valence electrons on the two metal rings above and below to form additional electrons, so they have the characteristics of electron compounds and it may produce a good nonlinear optical response. The static first hyperpolarizability (β0) of M3+–NO32−-M'3+ was calculated. The results show that the β0 value of Na3-NO3-Na3 is the largest (79067 × 10−30 esu.), which is 1163 times larger than that in the literature.