(C_9H_8N_6O_2)_n(n=1,2,3,4)分子体系非线性光学的理论研究(英文)

Theoretical Studies on NLO Properties of(C_9H_8N_6O_2)_n(n=1,2,3,4)

该文研究了(C9H8N6O2)n(n=1,2,3,4)分子体系的非线性光学性质,采用Hartree-Fock方法、密度泛函方法以及Mller-Plesset微扰理论方法在6-31G**基组下分别计算了该体系的静电场超极化率.其几何结构在B3LYP/6-31G**条件下进行了优化,发现它们有3种不同的氢键形式,其键长分别为0.196 3,0.191 8,0.190 9 nm.在HF/6-31G**水平下,发现一级超极化率(β0)的增长是由于随着n的增大,体系的氢键数目增加造成的,当n=1,2,3,4时,它们β0的值分别为246,596,1 067,1 555(原子单位),当n=1,2,3,4时,它们的二级超极化率(γ0)的值分别为1.4,4.3,7.8,11.5(104原子单位).结果显示随着n的增大,体系氢键数目的增加、相互作用的增强,Δγ也随着增大,在n=2,3,4时分别为14 768,35 627,58 670(原子单位).该研究显示氢键是设计非线性光学材料的关键因素.

The nonlinear optical （NLO） properties of （C9H8N6O2）n（n=1,2,3,4） have been investigated.The static （hyper）polarizabilities of the systems are evaluated by methods of the Hartree-Fock （HF）, Density Functional Theory （DFT）, and M？ller-Plesset perturbation theory at the second order （MP2） with 6-31G＊＊basis set.The structures are opti-mized at B3LYP/6-31G＊＊ level.There are three types of hydrogen bonds , N-H？O-C-C, N？H-N, and N-H？O-C-N, and their lengths are in average 0.196 3, 0.191 8 and 0.190 9 nm, respectively.At the HF/6-31G＊＊ level, the first hyperpolarizability （β0 ） is increased due to more and more hydrogen bond interactions involved as n is increased , i.e.β0 is 246, 596, 1 067, or 1 555 （ a.u.） for n=1, 2, 3, or 4, respectively.The static second hyperpolarizability （γ0） is 1.4, 4.3, 7.8, or 11.5 （in 104 a.u.）, respectively, for n=1, 2, 3, or 4.The results show that Δγfor n=2, 3 or 4 is 14 768, 35 627 or 58 670 a.u., which keeps increasing due to the interaction of more hydrogen bonds as n grows. Since Δγhas an obvious increase , it is attributed to the cooperativity of hydrogen bonds .The investigation shows that hy-drogen bond is an effective factor to design new NLO materials .