From owner-chemistry@ccl.net Fri Feb 20 12:11:00 2015
From: "Paul Popelier pla|-|manchester.ac.uk" <owner-chemistry=server.ccl.net>
To: CCL
Subject: CCL: QTAIM or else
Message-Id: <-51055-150220104636-14814-n8wt7cEuNgfDMtna2vqdeQ=server.ccl.net>
X-Original-From: "Paul  Popelier" <pla!^!manchester.ac.uk>
Date: Fri, 20 Feb 2015 10:46:35 -0500


Sent to CCL by: "Paul  Popelier" [pla]^[manchester.ac.uk]
Dear Lukman:

I do not at all agree with the statement of Prof Grimme saying that
"I don't think that QTAIM can give you a reasonable answer because its predictions are in serious disagreement with experimental data for a related case,"

This paper has been rebutted by Bader and also by myself in
The QTAIM Perspective of Chemical Bonding , P.L.A. Popelier in 
The Nature of the Chemical Bond Revisited, Chapter 8, pp 271-308 (pp 1-38), Eds. G. Frenking and S. Shaik, Wiley-VCH, 2014.    

For your convenience let me quote a relevant passage from this Chapter:

"Moreover, it should be emphasized that the German authors invoked the
architecture of the MM3 force field in order to separate molecular potential energy into chemically meaningful parts. Of course, this is the wrong way around. Indeed, popular force fields such as AMBER (or MM3 for that matter) have little authority, if any, when it comes to partitioning energy in a physically rigorous manner [63, 64]. The right way around is to construct a rigorous force field from an actual quantum mechanical energy partitioning scheme. Pivotally, however, the German authors used the arbitrary energy partitioning that underpins MM3 to support their main argument of the repulsive nature of H...H interactions. There is another and, quite frankly, better route however. If one is happy with the main
idea of topological partitioning, which is that of Quantum Chemical Topology (QCT), then one can trust IQA and proceed with it. The minimal quantity VAB xc that IQA offers provides a route to cut the vicious circle of interpreting bonding with schemes that impose bonding. Is it not safer to calculate a minimal and physically well-defined quantity and observe the bonding pattern it reveals rather than perpetuate primitive chemical intuition, by deciding a priori which interactions are bonds and which are not?"

Finally, you may be interested in the very recent work of a fellow South-African Professor called Jan Dillen, who published a very interesting and, in my opnion, correct paper on the meaning of H...H BCPs.
"Congested Molecules. Where is the Steric Repulsion? An
Analysis of the Electron Density by the Method of
Interacting Quantum Atoms"
International Journal of Quantum Chemistry 2013, 113, 21432153


Again, this work disagrees with Grimme's view.


Good luck with your research,

Paul


 

pla+*+manchester.ac.uk