From:	"Jan M.L. Martin" <comartin { *at * } wicc.weizmann.ac.il>
Date:	Fri, 31 Jan 1997 16:47:38 +0200 (IST)
Subject:	Re: CCL:Mulliken population analysis

On Thu, 30 Jan 1997, Stefan Fau wrote:

> Hi,
>
> there is another method of determining atomic charges, the NBO analysis of
> Reed, Weinhold and coworkers. The results quite independent of the basis
> set. Furthermore, the NBO analysis gives bond orders and the best Lewis
> stucture for the molecule. The NLMO part gives information on
> (hyper)conjugation.
May I put in a vote for Atomic Polar Tensor charges (J. Cioslowski,
JACS 111, 8333 (1989).

For a fairly systematic comparison of basis set and electron correlation
dependence of Mulliken, APT, NBO, and CHELP charges, see:

F. De Proft, J. M. L. Martin, and P. Geerlings, ``On the performance
of density functional methods for describing atomic populations, dipole
moments and infrared intensities'' Chemical Physics Letters
250, 393--401 (1996).

In a nutshell, Mulliken has the most severe basis set dependence but the
weakest correlation dependence, while the opposite is true for APT.
Furthermore, B3LYP APT charges are in excellent agreement with QCISD
ones with the same basis set. In effect, B3LYP APT charges with a basis
set of at least split-valence plus polarization quality will be close
to converged.

Topological (Bader) charges are furthermore considered in

P. Geerlings, F. De Proft, and J. M. L. Martin, ``Density-Functional
Theory Concepts and Techniques for Studying Molecular Charge Distributions
and Related Properties'', in Density-Functional methods in
chemistry (eds. J. Seminario and P. Politzer), Elsevier, 1996

Sincerely,
Jan M.L. Martin
----------------------------------------------------------------------------
dr. Jan M.L. Martin                 Senior Lecturer, Computational Chemistry
       Department of Organic Chemistry/Kimmelman Building, Room 262
            Weizmann Institute of Science/Rechovot 76100/ISRAEL
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