The Li-substituted effect on the geometries and second-order nonlinear optical properties of indeno[1,2-b]fluorene

In this work, we have designed a series of Li-substituted salts Lin@indeno[1,2-b]fluorene (n = 1-6) of substituted H atom(s) by Li atom(s) in indeno[1,2-b]fluorene. The studied systems are constructed by getting their global minimum energy. The second-order nonlinear optical responses of the studied systems are dominated by the number and the location of Li atoms. System 3 (Li atoms at 2, 3 and 4 positions) possesses the largest βtot value (18640 a.u.) at the MP2/6-31+G(d) level.