[molpro-user] UCCSD-F12 with CASSCF orbitals

[Kirk Peterson]

The workaround from Gerald is to follow your
CAS with an rhf step but set maxit=1. In 
the subsequent uccsd you'll need to set the
nocheck option. 

Kirk

Sent from my iPhone

On Aug 10, 2011, at 10:01 AM, binjiang.nju <binjiang.nju at gmail.com> wrote:

> Dear all,
>  
> I am trying to do a uccsd(t) calculation with CASSCF orbitals in Molpro.2010.1, it will be useful when two quasi-degenerate states exist and sometimes improve the convergence, comparing to the uccsd(t)/hf strategy. 
>  
> It works fine when I use only normal uccsd(t) option, but it fails when I use uccsd(t)-f12 option. I have tried to change the basis set, active space, as well as the type of CASSCF orbitals (Natural, Canonical), all of these do not help. Then I find some information for such problem, but still no suitalbe answer.
>  
> Gerald Knizia has mentioned that the F12 methods do request RHF reference functions, but he would try to fix this. (I cite his words in the following, hopefully he would not mind)
>  
> Dear all,
> the reason that F12 methods request RHF reference functions is related to 
> subtle issues with the the internal consistency of the respective methods 
> (open-shell vs closed-shell and the four combinations of density fitted vs 
> non-density fitted reference/correlation calculations).
> If I am not mistaken, for the CCSD methods (and maybe the non-density 
> fitted MP2-F12 methods) the current restrictions can be lifted such that 
> general reference functions are allowed. I will try to fix this and to 
> provide a patch for the current production version.
> -- 
> Gerald Knizia
> _______________________________________________
> ___________________________________________________
>  I am wondering that whether this issue has been solved or not. Is there any way to use CASSCF wavefunctions for UCCSD(t)-F12 calculations? Does anyone has other advise? Thanks in advance.
>  
> Best regards
> Bin
>  
>  
> 2011-08-10
> binjiang.nju
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> Molpro-user mailing list
> Molpro-user at molpro.net
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