二阶超极化率γ的Hartree-Fock极限值的再研究  

Further Study on Hartree-Fock Limit Values of the Second Hyperpolarizabilities γ

作　　者：刘柳斜[1] 丁涪江[1] 

机构地区：[1]四川师范大学化学系,成都610061

出　　处：《化学学报》2004年第17期1607-1611,共5页Acta Chimica Sinica

基　　金：四川省教育厅重点课题 (No.2 0 0 3A0 87)资助项目

摘　　要：用有限场 (FF)方法 ,在ROHF/x aug cc pVXZ (x =1～ 5或 7,X =T ,Q)水平上计算了C ,N ,O ,F ,OH和OH+ 等开壳层原子和分子、离子的二阶超极化率γ .与闭壳层原子和分子的计算结果相类似 ,γ随基组的增大出现一个拐点 .拐点对应的γ值与数字轨道计算的γ值符合得较好 ,其平均相对误差分别为 1 79% (x aug cc pVTZ)和 1 91% (x aug cc pVQZ) ,故计算二阶超极化率γ不需使用g函数 .进一步研究表明 ,用x aug cc pVTZ系列基组不仅可以得到γ的Hartree Fock极限值 。The second hyperpolarizabilities (γ) of several open shell atoms, ion and molecule C, N, O, F, OH and OH + have been calculated at ROHF/x-aug-cc-pVXZ level (x=0～5 or 7, X=T or Q) by finite-field method (FF). The γ exhibits a decided tendency toward smooth convergence as a function of the number of diffuse functions added to the standard cc-pVXZ sets (x-aug dependence) at first. Then when x is more than 4 or 5, γ blows up as a consequence. It is just as the situation in calculations of close shell atoms and molecules by coupled-perturbed Hatree-Fock method (CPHF). If the abscissa is x (the number of diffuse functions), then γ, as a function of x, shows an inflection point. And the γ values at inflexion points are good estimates for the Hatree-Fock limits. The average relative error of γ values at inflexion points is 1 79% for x-aug-cc-pVTZ and 1 91% for x-aug-cc-pVQZ respectively, so the x-aug-cc-pVTZ basis sets are suitable for calculations of hyperpolarizabilities. The second hyperpolarizability γ of Ne has also been calculated at CCSD(T)/5-aug-cc-pVTZ level by FF method, and the result is close to the experimental value. It has been found that the x-aug-cc-pVTZ basis sets are appropriate not only for SCF but also for high-level correlated calculations of the second hyperpolarizabilities.

关 键 词：二阶超极化率γ Hartee-Fock极限值 有限场 从头算 

分 类 号：O641[理学—物理化学]