[molpro-user] Gradients for CAS calculations

[nmarshal at hermes.ccqc.uga.edu]

Dear Molpro users,

A coworker of mine and I are trying to perform a geometry optimization on 
an open shell system with frozen core orbitals using CAS-SCF. I understand 
that analytical gradients are not available for this type of calculation, 
so we are attempting to use optg, numerical to compute the gradients by 
finite differences instead. However, the calculation still fails with the 
error message

 MCSCF GRADIENTS ONLY POSSIBLE WITH CLOSED-SHELL SCF FROZEN CORE ORBITALS
 ? Error
 ? FROZEN CORE ORBITALS NOT FOUND
 ? The problem occurs in FIND-ORB

I have put the relevant input sections below. Can anyone explain how to 
perform this calculation using finite differences? 

Thanks,

Nicholas Marshall
------------------------------------------------
 basis
   sp,na,cc-pVDZ
   sp,o,cc-pVDZ
   sp,n,cc-pVDZ
 end
                                                                                 
!  config
   rhf;wf,26,2,2;printorb,1;maxiter,200;                                         
                                                                                 
!optg;inactive,naon;
                                                                                 
!frequencies,sym=auto;
                                                                                 
!save,5300.2

   multi
                                                                                 
!  cpmcscf,grad,state=1.2
   occ,12,3
   core,6,1
   closed,10,2
   state,2
       noextra
       print,civector
    iterations;uncouple,1,to,24;end;
    maxiter,40;
                                                                                 
!ci
   optg,numerical
                                                                                 
! optg
   root,2
   method,rf
------------------------------------------------------