链式多Li掺杂分子H（HCN—Li）nH（n=1—6）的NLO性质及链长依赖性

NLO Property for the Multi Li-doped Chain Molecules H(HC==N—Li)_nH(n=1—6) and Dependence of Chain Length

对链式多Li掺杂体系H（HC==N-Li）。H（n=1～6）的结构与性质进行了研究．发现随着链长n的增大，体系中有两类分子出现．当n=1，2时，由于额外电子轨道是空的，从而形成了Li盐分子；而当n=3～6时，额外电子轨道是占据的，从而形成了具有大范围额外电子云的多Li电子化物分子．对于系列体系H（HC—N—Li）。H（n=1—6），其非线性光学（NLO）性质的依赖性呈现阶梯式增长的规律，即静态第一超极化率风的次序为2179，2776（n=1，2）〈5492，5487（n=3，4）〈15235，15377（n=5，6），表明增加Li原子掺杂数是提高NLO响应的新途径．

The alkali-metal doped system with excess electron is a new kind of potential materials having large non-linear optical( NLO) response. The structures and properties of the multi Li-doped chain molecules H( HC N—Li)n H( n = 1—6) were reported in this paper. Interestingly,with the increasing of chain length n,two kinds of molecules emerge. For n = 1 and 2,the Li-salt molecules are formed because the excess electron orbitals are unoccupied. But for n = 3—6,excess electron orbitals are occupied and multi-Li electrides with wide-range excess electron cloud are formed. For the multi Li-doped chain system,the dependence on NLO properties is unordinary stepped increase,2179,2776( n = 1,2) < 5492,5487( n = 3,4) < 15235,15377( n= 5,6). It demonstrates that multi-Li doping can generate wide-range excess electron cloud and large NLO response. The new knowledge enriches the design ideas for NLO materials.