# [molpro-user] rhf convergence problems

Jose A. Gamez joseantonio.gamez at uam.es
Wed May 19 10:21:30 BST 2010

```Dear Prof. Werner,

Thanks for the tip, it was really helpful. I just had to transform the natural
orbitals of multi into canonical ones to get the CCSD(T) energy.

Howerver, I got the rohf converged by using a positive shift for the open
orbitals

{rhf;
shift,-0.3,0.1;
wf,charge=-1}

arriving at the same energy as multi obtained. I guess that what this does is
to drag down in energy the closed orbitals and to push a bit up in energy the
open orbitals, but I can't see how this helps in convergence since then the
open orbitals will be closer to the virtual ones. Can anyone shed some light
on this?

Jose

On Sunday 16 May 2010 23:29:06 you wrote:
> This seems top be a difficult case, but you can converge it using
> multi, e.g.,
>
>   {rhf;maxit,20
>   shift,-0.3,-0.3;
>   wf,charge=-1}
>   {multi;occ,44;closed,43;wf,charge=-1;}
>
> Best regards
> Joachim Werner
>
> Am 12.05.2010 um 18:31 schrieb Jose A. Gamez:
> > Dear all,
> >
> > I'm trying to perform a CCSD(T) calculation on a radical-anionic
> > molecule.
> > However, I have great troubles to converge the ROHF calculation (the
> > UHF
> > converges OK). I've tried a couple of things:
> >
> > * I've used a smaller basis set (sto-3g and dvz, although the ROHF dvz
> > calculation didn't converge) RHF calculation as initial guess of my
> > ROHF
> > calculation.
> >
> > * I've used the restricted orbitals of the neutral molecule as
> > initial guess.
> >
> > * I've increased the value of the shift of the open orbitals up to
> > -0.3 .
> >
> > I think that the origin of this problem is that there is an excited
> > state
> > lying close to the ground state. But, since I optimised the UHF
> > wavefunction,
> > I would like to converge the ROHF.
> >
> > You have any tips?
> >
> > Thanks a lot for your help.
> >
> > Cheers,
> >
> > Jose
> >
> > P.D. I include the input file if that helps
> >
> > ***, CCSD(T) avtz calculation
> >
> > !basis=sto-3g
> >
> > geomtyp=xyz
> > geometry={
> > 8
> > Title
> >   Se           0.119746   -0.439567    0.252388
> >   Se           0.214836    0.063065    2.534400
> >    C           1.973623    0.030962   -0.199635
> >    H           2.638913   -0.492006    0.483666
> >    H           2.169261   -0.260569   -1.233496
> >    H           2.091656    1.105526   -0.073333
> >    O           1.479630   -2.438497    2.672993
> >    H           0.982562   -2.250200    1.856981
> > }
> >
> > !{rhf;
> > ! wf,charge=-1;
> > ! print,orbitals;
> > !}
> >
> > basis=vdz
> > rhf
> > {rhf;
> > shift,-0.3,-0.3;
> > wf,charge=-1}
> >
> > basis=avtz
> > !print,basis
> >
> > !rhf
> > {rhf;
> > wf,charge=-1;
> > shift,-0.3,-0.3;
> > ! print,orbitals;
> > }
> >
> > put,molden,CH3SeSeOH-TSOHan.TZ.molden
> >
> > pop
> > {pop;
> > density,spin}
> >
> > uccsd(t)
> > ---
> >
> >
> >
> > Departamento de Química, C-13
> > Phone: +34-91-497-3854
> > FAX: +34-91-497-5238
> > _______________________________________________
> > Molpro-user mailing list
> > Molpro-user at molpro.net
> > http://www.molpro.net/mailman/listinfo/molpro-user
>
--
Jose A. Gamez

Departamento de Química, C-13