[molpro-user] rhf convergence problems

[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)
---


-- 
Jose A. Gamez

Departamento de Química, C-13
Universidad Autonoma de Madrid
Cantoblanco, 28049-Madrid. Spain
Phone: +34-91-497-3854
FAX: +34-91-497-5238