自然电子轨道NBO分析方法

自然键轨道(NBO)分析方法

分子轨道未经定域化处理，将导致计算结果与我们通常的成键概念有所不同。例如在乙烯分子中，碳碳之间为双键，但在正则MO中，反映C与C之间成键作用的MO可能有多个，因此根据正则MO 的结果，我们无法断定C—C是单键还是双键。此时，通过对正则MO的定域化处理，可以得到通常意义上的成键图像。

正则MO的定域化处理方法较多，其中较为常用的是NBO方法，其使用方法是在输入文件中添加关键词：POP=NBO

以乙烯分子为例：

%mem=32mb

#p b3lyp/3-21g pop=nbo 进行NBO成键分析

The NBO analysis of ethylene

0,1

C

C,1,CC

H,1,CH,2,HCC

H,1,CH,2,HCC,3,180.,0

H,2,CH,1,HCC,3,180.,0

H,2,CH,1,HCC,4,180.,0

CC=1.31477

CH=1.07363

HCC=121.8867

Entering Link 1 = C:\G03W\l1.exe PID= 2100.

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