[molpro-user] making start command valid in optg

[Gabriel Freitas]

Dear Valérie and other collegues,

I would also appreciatte the modification in the code regarding the freedom
in choosing guesses for IRCs / geometry optimzations / frequencies
calculations.

Regarding the IRC step, you can choose it with the DIRECTION option in optg
directive. In addition to choosing the values +1 / -1 for positive and
negative directions, you can choose +n / -n (n natural), which exactly
determines the step lenght.

I had also a similar problem with some convergence problems with ROHF /
CCSD(T) IRCs, and I found out that it had a crossing of states near the
problematic point. Although CAS can sometimes change smoothly between
sates, but not always. So I think it's worthy to check the proximity of
excited states near these points (with SA-CAS)

I also had convergence problems calculation quasi-symmetrical structures
(for example, numerical frequencies near structures with symmetry higher
than C1), and it had nothing to do with excited states.

Regards,

-- 
Gabriel do Nascimento Freitas
D.Sc. Student - Graduate Program of Chemistry
Molecular Modelling and Theoretical Chemistry Laboratory - Room 412
Chemistry Institute - Universidade Federal do Rio de Janeiro (UFRJ) -
Brazil
(+5521)8830-9971 / (+5521)2562-7179

2011/11/22 Valérie Vallet <valerie.vallet at univ-lille1.fr>

> Dear Joachim,
>
> We have tried the failsafe option in the casscf block, but this does not
> improve the CASSCF convergence along the IRC.
> Could you please modify the molpro code so that we can force the casscf
> step to restart from HF orbitals?
> Would it also be possible to offer the possibility to change the step size
> in the IRC calculation, since this may help improving the CASSCF
> convergence along the IRC?
>
> Thanks a lot for your help,
>
> Valérie
>
> On Nov 20, 2011, at 5:33 PM, Hans-Joachim Werner wrote:
>
> > Dear Valérie and Jacky,
> > I will look at this. This was once changed to make sure that in geometry
> optimizations it always
> > uses the same options and starting orbitals from the previous
> calculation, which is normally most
> > sensible. I will make an option to disable this behavior. In the
> meantime you could try the
> > "FAILSAFE" option, which enables stricter convergence criteria. Perhaps
> that helps finding the correct
> > solution.
> > Best wishes
> > Joachim
> >
> >
> > --
> > Prof. Hans-Joachim Werner
> > Institute for Theoretical Chemistry
> > University of Stuttgart
> > Pfaffenwaldring 55
> > D-70569 Stuttgart, Germany
> > Tel.: (0049) 711 / 685 64400
> > Fax.: (0049) 711 / 685 64442
> > e-mail: werner at theochem.uni-stuttgart.de
> >
> >
> >
> > Am 18.11.2011 um 16:22 schrieb Valérie Vallet:
> >
> >> Dear MOLPRO users,
> >>
> >> We are trying to run an IRC path at the CASSCF level, and we are facing
> a case where the automatic CASSCF calculation that uses previous CASSCF
> orbitals along the reaction coordinate converges to the wrong energy, that
> is an energy higher than the that one would obtain with a single point
> calculation using Hartree-Fock orbitals.
> >>
> >> We thus would like to force the CASSCF to use HF orbitals instead at
> each geometry steps. However, it seems that the optg keyword ignores
> "start" commands in the MCSCF step. Is there an option that allows us to
> force optg to read "start" instructions?
> >>
> >> Thanks a lot for your help,
> >>
> >> Valérie Vallet
> >>
> >>
> >>
> >> ---
> >> Valérie Vallet
> >> Research assistant
> >> Laboratoire PhLAM, CNRS UMR 8523
> >> Université des Sciences et Technologies de Lille
> >> Bât P5
> >> F-59655 Villeneuve d'Ascq, France
> >> Tel: +33 3 2033 5985
> >> Fax: +33 3 2033 7020
> >> E-mail: valerie.vallet at univ-lille1.fr
> >> http://www.phlam.univ-lille1.fr/pub/f/themas/pcmt/
> >>
> >> _______________________________________________
> >> Molpro-user mailing list
> >> Molpro-user at molpro.net
> >> http://www.molpro.net/mailman/listinfo/molpro-user
> >
>
> _______________________________________________
> Molpro-user mailing list
> Molpro-user at molpro.net
> http://www.molpro.net/mailman/listinfo/molpro-user
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://www.molpro.net/pipermail/molpro-user/attachments/20111122/ca142d95/attachment.html>