Subject: Summary: Intramolecular Hydrogen Bond and AIM

From: Ari Lahti IFK <[email-masked]>
Date: Sat, 14 Dec 1996 14:02:34 +0200 (EET)

Dear CCLers,

Many thanks to all who responded to my query on Intramolecular Hydrogen
Bond and AIM. According to the replies summerized below, the AIM theory 
really is applicable to the evaluation of the strength of intramolecular
hydrogen bonds. It seems worthwhile trying AIMPAC, MORPHY, or EXTREME 
if Gaussian fails to identify the critical points. I also thank prof. 
Bader and dr Bayley, working in his group, for kindly delivering a copy 
of the AIMPAC program package. 

	best wishes
	--ari lahti

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* Ari Lahti, M.D., M.Sc.                          phone: +358 2 2654951     *
* Dept. of Phys. Chem.                            fax:   +358 2 2654706     *
* Abo Akademi University                          email: [email-masked]    *
* Porthansg. 3-5                                                            *
* FIN - 20500 Abo                                                           *
* Finland                                                                   *
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My original message:

>I make calculations on a small molecule that has an imidazole ring and 
>another ring formed by an intramolecular hydrogen bond. I would like to 
>evaluate the strength of this intramolecular hydrogen bond, and I'm
>wondering if the AIM theory might be useful in this respect. 

>The charge density at the critical point of a bond is supposed to correlate
>with the strength of the bond. Is this correlation linear in the sense that
>it lets one compare the strengths of intramolecular hydrogen bonds between 
>related molecules? Would this linearity make possible the evaluation of the
>strength of an intramolecular hydrogen bond in absolute terms also,
>through comparison of the charge density at the critical point of the
>system under investigation to that of a known model system? 

>I have made some preliminary calculations using the AIM card of
>Gaussian94. My calculations always end up with 'Hopf-Poincare condition not 
>satisfied', possibly because the program cannot handle the ring structures 
>of my molecule. The ring points are thus not given. However, the critical
>points of the covalent bonds and the intramolecular hydrogen bond are
>indicated. Are these results useful, or does the Hopf-Poincare error
>message mean that even data concerning these bond critical points are 
>corrupted? 

The replies:

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