Subject: DFT with 3-21G*

From: "Dr. Daniel Glossman-Mitnik" <daniel.glossman$at$cimav.edu.mx>
Date: Mon, 29 Sep 2003 16:52:40 -0600

Dear netters:

It is very usual to find papers where geometry optimizations
of medium and large molecules are performed with the 
Hartree-Fock method using the 3-21G* basis set. And this is
reported as giving almost as good geometries as HF/6-31G*
in a fraction of time (see, for example, the excellent recent 
book by Lewars). However, there are few examples in the 
literature about doing DFT optimizations with 3-21G* (the same
book quotes that they are very unsual, but doesn't state why).
Is there any important reason for not using 3-21G* in DFT
geometry optimizations, specially with large molecules? 
I have performed some calculations (very limited, of course)
and found that PBE1PBE/3-21G* gives geometries of similar
quality as PBE1PBE/6-31G*, in a third of CPU time.

Thanks in advance

                                       Dr. Daniel Glossman-Mitnik   

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Dr. Daniel Glossman-Mitnik
Centro de Investigación en Materiales Avanzados (CIMAV)
LAQUICOM - Laboratorio de Química Computacional
Miguel de Cervantes 120 - Comp. Ind. Chihuahua
Chihuahua, Chih. 31109 - MEXICO
Tel.: (52) 614 4391151
FAX: (52) 614 4391112
E-mail: daniel.glossman$at$cimav.edu.mx
            glossman$at$hotmail.com
            dglossman$at$yahoo.com
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