Density Functional Study of Nonlinear Optical Properties of Grossly Warped Nanographene C_(80)H_(30)

摘要

Recently, a grossly warped nanographene C_(80)H_(30) has been synthesized experimentally. Its optical properties are studied and compared with bucky ball C_(60), C_(70), and a flat nanographene C_(78)H_(30) in the framework of density functional theory (DFT) with the B3LYP functional. The static polarizability α, first-order hyperpolarizability β, and second-order hyperpolarizability y are calculated using the finite field approach. The average values of (α) and (γ) for C_(80)H_(30) are 151.7 A~3 and 54.5 × 10~(-35) esu, respectively, much higher than those of C_(60) and C_(70). Both (α) and (γ) of planar C_(78)H_(30) are higher than those of C_(80)H_(30), which is consistent with the fact that the energy gap of C_(78)H_(30) is smaller than that of C_(80)H_(30). However, the diagonal component of α along the z axis of C_(80)H_(30) is 86.2 A~3, much higher than 30.7 A~3 of C_(78)H_(30). Furthermore, the values of the hyperpolarizability in the z direction (y_(xxzz), y_(yyzz), and y_(zzzz)) of C_(80)H_(30) are almost 1 order of magnitude higher than those of C_(78)H_(30). The relationship between optical properties and electron delocalization in molecules indicated by aromaticity is also discussed. Our results indicate that C_(80)H_(30) can be used as a promising optical material.