Subject: Q: DFT on open shell systems

From: Frank Schaper <[email-masked]>
Date: Wed, 19 Jun 2002 16:13:47 +0200

Dear CCLers,

I have tried to calculate some organometallic complexes with unpaired
electrons (Turbomole). I'm a little bit surprised by the results, however.
In particular the calculated relative energies were much more sensitive to
the functional used (VWN vs. BP), changing form +100 kJ/mol to -100
kJ/mol, compared to my experiences with closed shell systems.

I would thus appreciate, if someone could help me with the following
questions:

- Is a strong dependence on the DFT-functional a "normal" behavior for
open-shell systems?

- Is there any way to take a shortcut for geometry optimizations? E.g.
calculating the geometry closed-shell and using single-point energies for
different open-shell spin states.

- Is a geometry optimization mandatory for every spin state (possible in
my case S=1, 3 and 5) or are single-point calculations sufficient? I'm
very much afraid they are not.

- Can the calculated energies of the same complex with different spin
states be compared directly or is the spin-pairing-energy missing to some
extend?

Thanks in advance

Hein

-- 
Frank Hein Schaper - AG Brintzinger - Universitaet Konstanz

email : [email-masked] - [email-masked]
        [email-masked]
web   : www.FrankSchaper.de

s-mail : Frank Schaper - AG Brintzinger - Universitaetsstr. 10
         78434 Konstanz