Subject: Replies to broken symmetry question

From: Anna Fuezery <fuzery!at!nmrfam.wisc.edu>
Date: Mon, 29 Mar 2004 16:55:36 -0600

Hi,

you need to turn of orbital symmetry. Mixing orbitals should not be
necessary
for non-singulet systems. Don't forget to used the unrestricted
algorithm (like
UB3LYP or so). It's also a good thing to have good starting orbitals.
Therefore
you might want to run a restricted calculation before and take the MOs from
there.

Hope this helps a little. Haven't done this for a long time.

Uwe

Anna Fuezery wrote:

>Hi everyone,
>
>I would like to carry out some broken symmetry calculations on di-iron
>clusters using DFT methods and the Gaussian program.  I have searched for
>articles on this subject, and although I have found many none seem to describe the
>practical aspects of how to do such calculations (eg. keywords to
>include in the input file).  Do I just include the Guess=Mix keywords in
>the route section or do I need to add anything else?  Furthermore, can I
>still use this option for di-iron clusters where one of the irons has been
>reduced (the Gaussian manual says the Guess=Mix keywords are for
>producing wavefunctions for singlet states and a reduced di-iron
>cluster would not fall in this category)?
>
>Any help is appreciated.  Thanks,
>
>
>Anna Fuzery
>University of Wisconsin - Madison
>Department of Biochemistry - John Markley Lab
>433 Babcock Dr.
>Madison, WI 53706-1544
>(608) 262-4687 ext. 3118
>fuzery!at!nmrfam.wisc.edu