Subject: ccl:g98 summary

From: Bernd Rieger <[email-masked]>
Date: Mon, 26 Apr 1999 15:03:21 +0200 (MDT)

Hi,

2 weeks ago I posted the following problem: 

> I did a UHF/LANL2MB SP calculation with G98 on a triplet state. After 
the 
> SCF has
> converged i found that the energie of the alpha HOMO was higher than the
> alpha LUMO. The same for beta orbitals.
> 
> Alpha  occ. eigenvalues --   -0.22532  -0.21631  -0.08415
> Alpha virt. eigenvalues --   -0.10304   0.00737   0.01977   0.03175   
0.03827
> 
> Beta  occ. eigenvalues --   -0.09456
> Beta virt. eigenvalues --   -0.10780  -0.07132   0.02100   0.02998   
0.03074
> 
> What happened? Is it possible that the VShift has something to do with it?
> I could not set it to zero even with SCF=(VShift=0). Also the symmetry of
> the orbital is not found correctly at the end of the SCF.
> Does anybody know why this happened?

I got 2 responces:

1. Perhaps you're studying transition metals. The energy inversion 
   is very often In those cases when the vshift is activated. 
   Did you try iop(5/10=-1)
   in the route section to disable vshift?

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2. There are a number of possibilities.  1) you may have failed to converge
   to the lowest triplet due to symmetry.  2) vshift has trapped you into
   a higher state 3) the triplet is quite high lying.  In looking at the
   eigenvalues the fact that you have a very negative "virtual" I would agree
   that 1) or 2) see most likley.
   From the checkpoint file you can try GUESS=(Read,Alter) to switch
   these orbitals.  Another alternative is to use STABLE=OPT which will
   actually solve for the stability of the wavefunction and re-optimize
   the SCF if it finds a lower state.

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I tried IOP(5/10=-1) to set VSHIFT=0 and found that the
occ. orbitals were lower in energy than the virt. orbtials as one would 
like to have it. So  indeed it seemed to be a problem of VSHIFT with 
transitions metals. 

thanks

Bernd

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| Bernd Rieger                         Phone:089 289 13768           |
| Physic Department T38, TU Muenchen   Fax:  089 289 12444           |
| James-Franck-Strasse                                               |
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