CCL:G: G- How to retain the symmetry in a SCF calculation ?



 Sent to CCL by: "Johannes Hachmann" [jh388!A!cornell.edu]
 Hi Ding,
 use SCF=QC (however quadratically convergent SCF is a bit costy...). See
 description under http://www.gaussian.com/g_ur/k_guess.htm on the bottom
 together with GUESS=ALTER. This is not a particularly elegant way to do
 things (compared to just specifying the state symmetry in e.g. MOLPRO) but
 it works. You might want to use the STABLE option so that you know whether
 you have instabilities to which other states and which additional MO swaps
 you might want to perform.
 Best
 Johannes
 ---------------------------------------------------------------
 Johannes Hachmann
 (Dipl.-Chem., M.Sc.)
 Chan Research Group
 140D Baker Laboratory
 Department of Chemistry and Chemical Biology
 Cornell University
 Ithaca, NY 14853-1301
 USA
 ---------------------------------------------------------------
 > -----Original Message-----
 > From: owner-chemistry+jh388==cornell.edu,,ccl.net
 > [mailto:owner-chemistry+jh388==cornell.edu,,ccl.net] On Behalf
 > Of xunlei ding dingxunlei::gmail.com
 > Sent: Friday, February 13, 2009 3:42 AM
 > To: Hachmann, Johannes
 > Subject: CCL:G: G- How to retain the symmetry in a SCF calculation ?
 >
 >
 > Sent to CCL by: xunlei ding [dingxunlei.:.gmail.com] Dear CCLers,
 >
 > In the manual of G03, the key word "SCF= Symm" is discribed as
 below:
 > Retain all symmetry constraints: make the number of occupied
 > orbitals of each symmetry type (abelian irreducible
 > representation) match that of the initial guess. Use this
 > option to retain a specific state of the wavefunction
 > throughout the calculation. It is the default only for GVB
 > calculations.
 >
 > But sometimes it doesn't work and the last state is different
 > from the initial state.
 >
 > Could you give me more suggestions on how to retain the
 > symmetry in a SCF calculation?
 >
 > Thanks!
 >
 > Best regards,
 > Ding
 >
 >
 >
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