MRCI crashes with too many orbitals error

[Joris Kuipers]

Dear molpro users!

I'm struck upon a strange problem. My MRCI calculation crashes with the message 
"too many active orbitals 24 this version allows only 16". The fact that you can only use 
16 active orbitals is known to me but no matter how I configure my active space (much 
smaller than 16 orbitals) the CI program crashes. Let me illustrate this with two 
examples:

My input reads for Pt4:

  hf
  multi
  core,5,3,3,1,5,3,3,1
  closed,7,4,4,2,7,4,4,2
  occ,10,4,4,2,10,4,4,2
  ci

Clearly there are 6 active orbitals and 10 closed shell orbitals so the multi program runs 
just fine (4 electrons and 57 CSF's) but the ci program crashes with this error message. 
Then my question obviously is: how does the ci program make up these 24 active 
orbitals?? It is not just the sum of closed + active which you might expect if the ci 
program does not deal with the active space as efficiently as the multi program.

Another example:

  hf
  multi
  core,7,4,4,2,7,4,4,2
  occ,10,4,4,2,10,4,4,2
  ci

Now there are 34 orbitals in the core and only 6 active orbitals. Still, the ci program 
crashes with the message that I'm using 24 active orbitals.

I've already tried to take other orbitals and other numbers of electrons into account but 
that had no effect. Strangest thing is that the following input for Pt2:

   hf
   multi
   core,2,1,1,0,2,1,1,0
   closed,4,2,2,1,4,1,1,1
   occ,6,3,3,1,6,2,2,1
   ci

works fine! Can anybody please give their insights? I'm puzzled.

Thanks for your time.

Kind regards,

Joris Kuipers



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