摘要
提出一种计算量小的构造合理最紧缩定域化轨道的方法 .非正交定域轨道 ( NOLMO)没有“正交化尾巴”,比正交定域轨道 ( OLMO)更局域化、更紧缩、更具可移植性 ,从而更适合用于化学问题的理论研究 .但若在用变分法确定最大限度局域化 NOLMO时单纯取消正交条件而不附加其它的限制 ,会得到趋于线性相关的不合理结果 .提出用强制 NOLMO与投影自然键轨道 ( PNBO)的重心重合代替正交化条件确定合理的最大限度局域化 NOLMO(合理最紧缩定域轨道 )的方法 .对一系列不同类型分子的计算结果表明 ,用该方法可以得到空间分布合理及线性独立的 NOLMO,延伸度与文献已有的最佳结果接近 ,而计算量大幅度降低 .由于构造投影自然键轨道的计算量随分子中原子数目的增加只是线性增长 ,因此 。
A method is proposed to construct the reasonable and most contracted localized orbitals with less computational efforts. The non-orthogonalized localized orbitals(NOLMOs) do not possess 'orthogonalization tails', thus they are more localized and contracted, and more transferable comparing to the corresponding orthogonalized localized orbitals(OLMOs). Therefore, they are more suitable for use in theoretical study of chemical problems. However, if the orthogonalization requirement is simply removed without imposing other constraints when one intends to construct the most contracted NOLMOs by variation, unreasonable results may be obtained: the NOLMOs tend to linear dependence or they are ill-conditioned linear independence. In this paper, it is proposed that constraining the centriods of NOLMOs at those of the corresponding projected natural bond orbitals(PNBO) can be used to replace the orthogonalization requirement for constructing the reasonable NOLMOs contracted as far as possible(the reasonable most contracted localized orbitals). The calculated results for a series of different kinds of molecules show that, by means of the proposed method, the obtained NOLMOs are linearly independent and reasonably distribute in space, and their spreads are very close to the best results presented in literatures, while the computational efforts decrease considerably. The proposed method can be used to construct the reasonable and most contracted NOLMOs in very large systems due to the fact that the computational efforts for constructing PNBOs only linearly increase with the increase of atoms in systems.
出处
《高等学校化学学报》
SCIE
EI
CAS
CSCD
北大核心
2004年第7期1291-1297,MJ04,共8页
Chemical Journal of Chinese Universities
基金
国家自然科学基金 (批准号 :2 0 3 3 3 0 2 0 )资助 .
