Subject: Re: CCL:Basis sets for transitional metals

From: Mikael Johansson <mpjohans^at^pcu.helsinki.fi>
Date: Wed, 21 Apr 2004 14:26:40 +0300 (EEST)

Hello Liu and All!

On Wed, 21 Apr 2004, li wrote:

> I am using G98 now, and I am trying to get the electronic structure of
> CO molecule. By using all the methods implemented in G98, I found that
> all the result give a similar result - O gets charges from C and has a
> negative charge. This is quite different from the description I found in
> books, C should get charge from O and has a negative charge. This makes
> me confused.

That should not be true. Calculate the dipole moment with some correlated
methods, and you should get a negative carbon. HF (with a sufficient basis
set) gets it wrong, though. Don't believe in Mulliken charges here!

Have a nice day,
    Mikael J.
    http://www.helsinki.fi/~mpjohans/

---

From: Errol Lewars <elewars!at!trentu.cA>
Date: Wed, 21 Apr 2004 10:26:15 -0400

2004 April 21

Hello,

Reproducing the dipole moment of carbon monoxide is a known problem in
computational chemistry. See e.g. C. J. Cramer, Essentials of
Computational Chemistry, pp. 268-269. The experimental moment is 0.11 D
(with C negative, apparently, from molecular beam resonance
measurements). An accurate calculation used the DFT B3LYP functional and
a big basis set (A. J. Cohen and Y. Tantirungrotechai, Chem Phys Lett,
1999, 299, 465).

E. Lewars
===

li wrote:

>Hi!
>
>I am using G98 now, and I am trying to get the electronic structure of CO molecule. By using all the methods implemented in G98, I found that all the result give a similar result - O gets charges from C and has a negative charge. This is quite different from the description I found in books, C should get charge from O and has a negative charge. This makes me confused. 
>
>What should I do to make a correct calculation of CO? 
>
>I hope that you would not mind giving me some detailed instruction on the calculation.
>
>Sincerely yours
>
>Xin, Liu
>
>
>
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