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Re: inadequate mulliken charges and bond orders

Fumihito Mohri
qzg00677@nifty.com

Dear Andrii Kulinich
>here the results of B3LYP (basis 6-31G*(d,p)) calculation
The correct symbol of basis set you used is 6-31+G(d.p). This set includes diffuse
functions for non-hydrogen atoms. 'Abnormal' charges and bond orders come from
the diffuse functions. Please set DIFFSP=.FALSE., and you will get the charges and
the bond orders with their 'normal' values.
However, it is well known that Mayer bond order exhibits large basis set dependence.
Please study papers related to Mayer bond-order. For exmaple,
A. J. Bridgman et al. J. Chem. Soc. Dalton Trans. (2001) 2095
G. Lendvay, J.Phys. Chem. vol.93(1989) 4422.

>For the smaller basis set (STO) everything was OK.
Atomic valence calculated from minimal basis set does not exceed its classical
value. For, example,carbon valence calculated from STO-3G does not exceed 4.
In other word, at lesat for an organic compound, the minimal basis set often
brings the atomic valences with 'very normal' values.

Best regards,
Fumihito Mohri

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