[molpro-user] Problem with RS2 using reference SA-CASSCF averaged over different ionization/spin states

[Werner Győrffy]

Dear Seth,

The CASPT2 gradient code uses spin-adapted CSFs and therefore cannot 
treat states of different spin symmetry in the SA-CASSCF.

Regards,

Werner.

On 21.09.2017 15:09, Seth Olsen wrote:
> HI Molpro-User,
> 
> I’m trying to use the RS2 gradient engine to optimize the structure of 
> one state from a SA-CASSCF reference averaged over four different states 
> with different spin and electron number (singlet, triplet, oxidized, 
> reduced states).  I want to optimize the singlet, but I am running into 
> a problem.  The RS2 doesn’t want to work, and complains that the spin is 
> wrong.  It objects to the specification of a singlet state symmetry, and 
> stops with an error stating that ms2=2 was used in the SA-CASSCF (this 
> is not true, really; the SA-CASSCF was averaged over both singlet and 
> triplet states as the attached output will show).  What am I doing 
> wrong?  The complete output (bzipped) is attached.  Here are the multi & 
> rs2 decks:
> 
> {mcscf
>   start,2140.2
>   occ,49
>   closed,43
>   config,det
>   wf,90,1,0
>   state,1
>   wf,90,1,2
>   state,1
>   wf,91,1,1
>   state,1
>   wf,89,1,1
>   state,1
>   canorb,2140.2;dm
>   }
> 
>   {rs2
>   orbit,2140.2
>   occ,49
>   closed,43
>   core,17
>   noexc
>   wf,90,1,0
>   state,1,1
>   }
> and here is the error message:
>   Number of optimized states:  1  Roots:   1
>   Number of reference states:  1  Roots:   1
> 
>   ms2=0 but ms2 was 2 in mcscf
>   ? Error
>   ? Inconsistent Spin
>   ? The problem occurs in check_rs2occ
> 
>   GLOBAL ERROR fehler on processor   0
> 
> 
> Many Thanks,
> Seth
> 
> 
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