Chemistry Reference
In-Depth Information
The Source Function Descriptor as a Tool to
Extract Chemical Information from Theoretical
and Experimental Electron Densities
Carlo Gatti
Abstract This chapter deals with the source function (SF) descriptor, originally put
forth by Bader and Gatti back in 1998. After a brief review on how this descriptor is
defined and what it physically represents, the various forms through which the SFmay
be analyzed are presented in some detail. The relationships between atomic SF
contributions and chemical bond nature are analyzed in some prototypical cases,
and the capability of the SF to neatly reveal
-electron conjugation directly from
the electron distribution and independently from any MO scheme or decomposition is
introduced. Applications of the SF to chemistry from the literature are reviewed and
critically discussed, including the use of the SF to assess chemical transferability or to
describe chemical bonding in challenging situations, like for instance the short-strong
hydrogen bonds in
p
-conjugated frameworks or the metal-metal and metal-ligand
interactions in the organometallic complexes. Comparison with the insight obtained
from other bond topological descriptors is given, emphasizing the special role the SF
has of being directly derivable from experimental electron density distributions and to
so provide an ideal tool to compare experiment and theory. The robustness of the SF
descriptor against changes in the models used to derive electron densities from theory
of experiment is detailed. First results on using the SF to define an unambiguous full
population analysis are outlined. The possible ways of further decomposing the atomic
SF in chemically meaningful additive pieces, such as core and valence atomic con-
tributions, are analyzed in view of their potential insight and degree of arbitrariness.
p
Keywords Chemical transferability
Electron conjugation
Local and nonlocal
bonding descriptors
Short-strong hydrogen bonds
Source function and chemical bonding
Theoretical
and experimental electron densities
Metal-metal and metal-ligand bonds
Population analysis
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