Subject: AIM throughout the ages

From: "Alexandre Hocquet" <[email-masked]>
Date: Wed, 19 Jun 2002 14:22:49 +0200

Dear CCLers,
We have been working on hydrogen bonding and AIM for a few months now, and
we are currently taking a great interest in resonance assisted hydrogen
bonds.

We found that a formamide dimer had been studied with an AIM analysis a long
time ago (Cheeseman J.R., Carrol, M., T., Bader R., F., W., Chem Phys Lett
1988, 143, 450-458) using criteria that seem to be very little used since
then.

 In particular, we were wondering why the idea of studying the ellipticity
along the bond path was no longer used in later publications on the subject.

 In the same publication, all the atoms were integrated, and there was a
separation of the populations of the atoms between pi and sigma electrons.

 Practically, How can the wavefunction file (given by a Gaussian
calculation) be split between sigma and pi for further topological analysis
?

This kind of pi/sigma analysis seems to have also disappeared in more recent
publications on the subject...

Any hints ?

------------------------------------------------------------
Alexandre HOCQUET
Laboratoire de Physicochimie Biomoléculaire et Cellulaire
UMR CNRS 7033
[email-masked]
Fax: 33 1 44277560
LPBC, case courrier 138
4 Place Jussieu, 75252 PARIS Cedex 05 France
------------------------------------------------------------

---

From: "Curt M. Breneman" <[email-masked]>
Date: Thu, 20 Jun 2002 09:07:15 -0400

Dear Alexandre,

The major reason why the AIM sigma/pi separation strategy is rare in recent
literature is that it may only be used for planar molecules. The original PROAIM
code required the user to designate which molecular orbitals were to be included
in the integration, leaving it to the user to identify orbitals of the proper
symmetry.  There were some interesting results that came from sigma/pi analysis,
but all-electron analysis is more general.

Bond critical point ellipticities are still useful for elucidating the character
of interatomic interactions, but other approaches that are not limited by
molecular geometry (such as Jerzy Cioslowski's BONDER method) have been used to
probe bond types.

Curt Breneman
RPI Chemistry

Alexandre Hocquet wrote:

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