Subject: Re: Comparison of current DFT codes?

From: [email-masked] (David Case)
Date: Wed, 3 Nov 93 07:41:35 PST

> 
> At this moment, I'm trying to make a decision on which code to use to
> investigate the effects of conformational energetics on redox and
> electronic spectroscopic properties of a series of polynuclear Co(III)
> complexes that we have synthesised in our labs. 

We have been please with the "ADF" (Amsterdam Density Functional) codes in
our calculations on polynuclear iron-sulfur, iron-oxo and manganese-oxo
clusters.  For an overview of this work, see Adv. Inorg. Chem. 38:423-470 
(1992).  ADF is supplied in source code format, so you can examine the
details of the calculations and make modifications if you wish.  ADF uses
Slater type orbital basis sets, which appear to do a good job, and the
overall approach has been widely tested -- see e.g. the review by Tom 
Ziegler,  Chem. Rev. 91:651-667 (1991).

The ADF programs can place some severe constraints on your cpu and
available disk space.  We have also made considerable use of DGauss for
transition-metal complexes, and are generally pleased with it, although
we have not yet figured out how to carry out broken symmetry
calculations on multi-metal systems with it.  DGauss is a part of a
package called Unichem, which is distributed by Cray Research and by
MSI.  It uses Gaussian basis sets. There is a consortium which helps to
support its development;  members of the consortium receive 
updates about a year or so in advance of other users.  As far as I
know, it is not possible to a source code license for DGauss.

Our experience with DMol on fairly large clusters (three dozen atoms or so
with two transition metals) has been mixed, with troubles arising in obtaining
self-consistency.  But we have never run a side-by-side test to see whether
the problems are intrisince to these molecules or reflect somehow on the code.
DMol uses partially numerical basis sets.

It is difficult to compare the three codes because of the difference in
philosophy, accuracy requirements, and basis sets.

...dave case

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David A. Case                      |  internet: [email-masked]
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