[molpro-user] Multi with F12?

[Kirk Peterson]

Hi Terry,
 For using multi for your HF, just invoke multi where you would normally call hf but include
occ and closed cards to restrict it to a single determinant.  Also output the orbitals as type
canonical.  In the rccsd-f12a calculation, specify the record of these orbitals to read in and you might have
to also include a "ignore_error" option on the orbital directive since usually the ccsd(t) code doesn't
like what looks like non-canonical orbitals for the (t) step.

regards,

Kirk


On Sep 22, 2010, at 2:55 AM, Terry Frankcombe wrote:

> Hi folks
> 
> I'm trying to run optimisations on a triplet system using the RCCSD-F12A
> method, but the RHF step is regularly failing with no convergence when
> stepping the geometry to calculate a force.  Changing the level shifts
> helps sometimes, but it's getting rather annoying.
> 
> I've seen it stated in a few places that the molpro team often use multi
> for doing SCF, as the algorithm is more robust.
> 
> Is there a simple way to get RCCSD-F12A to use multi in preference to
> the SCF code inside an optimisation?
> 
> Regards
> Terry
> 
> 
> -- 
> Dr. Terry Frankcombe
> Research School of Chemistry, Australian National University
> Ph: (+61) 0417 163 509    Skype: terry.frankcombe
> 
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