# ccl:g98 summary

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 |
| 85748 Garching email: brieger : at : physik.tu-muenchen.de |
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