【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 .0 9nm更多还原

【Abstract】 In 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.更多还原