Replies to broken symmetry question

[Anna Fuezery <fuzery!at!nmrfam.wisc.edu>]

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