CCL: AIM charges - HF or DFT?



 Sent to CCL by: Eduard Matito [ematito===gmail.com]
 Dear David,
 
First of all, is a HF or a DFT wave function better? What about the hybrid=
 B3LYP?=20=20
 
B3LYP geometries are far better than HF ones, but HF is actually the best monodeterminantal wavefunction by definition, so I would rather consider using HF wavefunction. In addition to QTAIM charges a useful tool for the analysis of the electron distributions are the so-called localization/delocalization indexes (LI and DI).
 See for instance the following papers:
 
X. Fradera, M. A. Austen, and R. F. W. Bader, J. Phys. Chem. A, 1999, 103, 304. J. Poater, M. Sola, M. Duran, and X. Fradera, Theo. Chem. Acc., 2002, 107, 362.
 
Second, is a large basis set still considered to be important? What about =
 diffuse functions?=20=20
 
Most of these 3-D molecular space decomposition schemes (as QTAIM or fuzzy-atom) are less sensible to basis set dependence than the Hilbert-space counterparts. Unlike Hibert space analysis, which needs of atom centered functions, 3D schemes do not have problems to use diffuse or bond functions.
 
Third, I am considering purchasing AIM2000. Are AIM2000 users satisfied? = Does it have limitations I should be aware of? Is there competing software= I should consider? For non-computational-chemistry reasons, I have only W=
 indows XP operating system.
 
The group of Bader gives the PROAIM program for free. It contains all applications needed for the calculation of QTAIM properties. The good points of AIM2000 are its nice graphical interface and that the calculation of LI and DI are done automatically (however you can easily write a 50lines code to calculate DIs and LIs
from *.int files generated with PROAIM for a monodeterminantal
 wavefunction).
 Hope it helps,
 Eduard Matito
 Institute of Computational Chemistry
 University of Girona (Spain)
 e-mail: eduard(at)iqc.udg.es
 http://iqc.udg.es/~eduard