[molpro-user] Open shell CC woes

[Mikael Johansson]

Dear Kirk,

Thanks for the hint on how to use previous orbitals, that one works! The 
reusing of orbitals, that is; the larger basis set SCF's still converge to 
the wrong states, up to 1 hartree above energies encountered during the 
SCF, with no help from playing around with level shifts and stuff :-/ So 
I'll try some other tricks, like slightly breaking the degenerate 
symmetry.

Have a nice day,
     Mikael J.
     http://www.iki.fi/~mpjohans/


On Wed, 17 Mar 2010, Kirk Peterson wrote:

> Dear Mikael,
>
> since it sounds like a smaller basis set works ok, just follow your current input with
> another set that is identical (starting from the basis set block) except for changing the basis set to VTZ.
> The second ROHF will pick up the last set of orbitals even if a different basis was used.
>
> regards,
>
> Kirk
>
> On Mar 16, 2010, at 4:43 PM, Mikael Johansson wrote:
>
>>
>> Hello All!
>>
>> I'm trying to compute the energy difference between the doublet and sextet
>> states of D3h symmetric FeF3 at CCSD(T) level (in C2v). I'm having great
>> difficulty in converging the sextet state ROHF, which surprised me, as it
>> should be the ground state. The doublet I got to converge.
>>
>> Now, I haven't done any open-shell calcs with Molpro before, so perhaps
>> I'm just doing something wrong. I would appreciate it if someone would
>> care to comment if even my input structure is correct. Also any general
>> comment on the usefulness of computing spin state splittings with RCCSD(T)
>> are most welcome.
>>
>> For the sextet I've used the following input:
>>
>> {rhf,maxit=500;
>> occ,14,8,5,2;
>> closed,12,7,4,1;
>> wf,53,1,5}
>> rccsd(t),maxit=500
>>
>> And for the doublet, the following:
>>
>> {rhf,maxit=500;
>> occ,13,7,5,2;
>> closed,12,7,5,2;
>> wf,53,1,1}
>> rccsd(t),maxit=500
>>
>> The complete input is at the end of the mail. But as mentioned, the sextet
>> ROHF just refuses to converge with a basis bigger than Ahlrichs-VDZ (or
>> converges to a local minimum). Is it possible somehow within Molpro to
>> expand a converged lower basis set solution onto a larger basis set? I
>> tried to google for that, unsuccessfully.
>>
>> I'm using 2006.1 patch level 151 in case it matters. Any help with this
>> would be most appreciated!
>>
>> Have a nice day,
>>     Mikael J.
>>     http://www.iki.fi/~mpjohans/
>>
>>
>> ***,FeF3-sextet
>> memory,80,m
>> GPRINT,orbital
>> GTHRESH,twoint=1.d-13
>> set,charge=0
>> geomtyp=xyz
>> file,1,FeF3-6-pVTZ-s.int
>> file,2,FeF3-6-pVTZ-s.wfu
>> punch,FeF3-6-pVTZ-s.punch
>> geometry={
>>    4
>>        FeF3 experimental D3h
>> Fe         0.00000        0.00000        0.00000
>> F          0.88150        1.52680        0.00000
>> F          0.88150       -1.52680        0.00000
>> F         -1.76300        0.00000        0.00000
>> }
>> basis={
>> spdfg,Fe,cc-pVTZ;C
>> spdf,F,cc-pVTZ;C
>> }
>> {rhf,maxit=500;
>> occ,14,8,5,2;
>> closed,12,7,4,1;
>> wf,53,1,5}
>> rccsd(t),maxit=500
>>
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>
>