单占据片断轨道的组合式(Kost+Perkin)定域化  

Localization of a Combinatorial Procedure for Singly Occupied Fragment FMOs

作　　者：虞忠衡[1] 郭彦伸[1] 彭晓琦[1] 宣正乾[1] 

机构地区：[1]中国科学院化学研究所分子动态稳态国家重点实验室,北京100080

出　　处：《高等学校化学学报》2001年第10期1715-1719,共5页Chemical Journal of Chinese Universities

基　　金：国家自然科学基金 (批准号 :2 9872 0 42 ;2 0 0 72 0 41;2 0 0 32 0 1)资助

摘　　要：为了使开壳层片断轨道具有正确的集居数 ,正则轨道必须定域化 .但是 ,在确保目标轨道Φsdan单占据性的同时 ,Kost定域化也破坏了 Φs特定的对称性 .实际计算表明 ,Perkin定域化可以弥补 Kost程序的缺陷 ,将单占据的 Φs转化成高度定域的、对称的片断轨道 .在片断分子中 ,C—HR键长 r的选择和 Kost定域化的方式对 Perkin定域化的成败具有重大的影响 .当 Gaussian基组为 STO-3G,3-2 1 G和 4 -31 G时 ,r应为0 .1 nm;但在 6-31 G水平下 ,必须 r =0 .0In order to ensure that each of all opened shell\|fragment MOs (FMO \%Φ\-i\%), obtained from the UHF computation for a molecular fragment, has a correct electronic occupancy, the FMOs \%Φ\-i\% have to be localized. However, the specified symmetrization of the singly occupied FMOs (\%Φ\-s\%) is destroyed while \%Φ\-s\% becomes singly occupied after the Kost localization. The Perkin localization, a computational procedure after the Kost localization, transforms \%Φ\-s\% into \%φ\-s\% which possesses now the symmetrization which they should have. The way of the Kost localization and setting of the length of the bond C\|H\-R between the carbon atom and its referential hydrogen atom H\-R have great effects on the symmetric characters of the localized FMOs obtained from the Perkin localzation. In the case of the Gaussian basis sets such as STO\|3G, 3\|21G and \{4\|31G\}, the bond length \%r\% should be set to 0.1 nm, and when 6\|31G is used, it should be 0.09 nm.

关 键 词：Kost定域化 Perkin定域化 片断分子轨道 片断分子 有机化学 共轭效应 芳香性 

分 类 号：O621.13[理学—有机化学]