On Fri, Mar 6, 2009 at 8:48 AM, Johannes Hachmann jh388||
cornell.edu <owner-chemistry /at\ccl.net> wrote:
Sent to CCL by: "Johannes Hachmann" [jh388(0)cornell.edu]
Hi John,
obviously you are usually interested in the proper electronic ground state - but
being interested in e.g. spin gaps, or a comparison of the electronic
structure/orbital sets of different spin states, or in a specific starting guess
for a post-HF calculation (which happens to be not the ground state) is not that
far fetched... Then it doesn't really help you if your calc always falls
back on the ground state which has a symmetry that's not of interest for
you.
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 John McKelvey jmmckel__gmail.com
> Sent: Thursday, March 05, 2009 12:12 PM
> To: Hachmann, Johannes
> Subject: CCL:G: G- How to retain the symmetry in a SCF calculation ?
>
> Is the possibility of finding a symmetry of lower energy _all
> that bad_? I can think of an obvious reason why it would be
> beneficial....
>
> Cheers,
>
> John McKelvey
>
>
>
> On Wed, Mar 4, 2009 at 11:19 PM, Johannes Hachmann jh388 ~~
> cornell.edu
<owner-chemistry{}ccl.net> wrote:
>
>
>
> Sent to CCL by: "Johannes Hachmann"
[jh388_._cornell.edu]
> Hi Ding,
>
> sorry, never ran into this problem. Note that you
might
> have to try a number of orbital swaps to get to the
> wavefunction irrep you want. Also, in case you use the STABLE
> keyword, DO NOT use STABLE=OPT because that will likely bring
> you back to a more stable wavefunction of different symmetry.
>
> Hope that helps
>
> 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
> <mailto:owner-chemistry%2Bjh388> ==cornell.edu]|[ccl.net] On Behalf
> > Of xunlei ding dingxunlei:_:gmail.com
> > Sent: Wednesday, March 04, 2009 5:12 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 Johannes,
> >
> > Sometimes scf=QC works but not always.
> > I hope there be a better way for this
problem.
> >
> > It seems that we can use IOP, as is described
as:
> >
> > IOp(5/15)
> > Apply Abelian symmetry constraints on
orbitals.
> >
> > 0 Default (1 for L502,
2 for L501 and L506).
> > 1 No.
> > 2 Yes, keep occupation
of each irrep the same as the
> > initial guess.
> > 3 Yes, keep overall
wavefunction the same as
> the initial guess,
> > but doing the minimal amount
> > of orbital
switching to accomplish this.
> > 00 Default (use Abelian
symmetry in diagonalization).
> > 10 Use Abelian symmetry in
diagonalization.
> > 20 Do not use Abelian
symmetry in diagonalization.
> >
> > But in my test, iop(5/15=2) doesn't work.
> >
> > Any more suggestions?
> >
> > Thanks a lot!
> >
> > Best regards,
> > Ding
> >
> >
> >
> > 2009/2/13 Johannes Hachmann jh388[*]cornell.edu
> > <owner-chemistry||ccl.net>:
> > >
> > > 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
> <mailto:owner-chemistry%2Bjh388> ==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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> >
> >
> >
> > --
> >
------------------------------------------------------
> > Xun-Lei Ding
> > Associate Research Professor of Physical
Chemistry State Key
> > Lab for Struct. Chem. of Unstable and Stable
Species
> > Institute of Chemistry, The Chinese Academy of
Sciences
> > Zhongguancun North First Street 2，
> > Beijing 100190, P. R. China
> > Phone 86-10-62568330
> > Fax 86-10-62559373
> >
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