[molpro-user] CI vector: the role of the observer (?)

[Tim Robinson]

Hi all,

I see different behaviour in the CI vectors, depending on whether I save 
the vector or don't save it.  For example, a simple CASSCF calculation on 
formaldehyde produces the following CI vector info (print threshold at 
0.04)

 CI vector
 ---------

 20 20 20       0.9769517
 20 02 20      -0.1360811
 02 20 20      -0.0560268
 20 20 02      -0.0548364
 -+ +- 20      -0.0523983
 +- -+ 20      -0.0523983
 20 -+ +-      -0.0459565
 20 +- -+      -0.0459565

 TOTAL ENERGIES                      -113.98318578

... whereas if I say I want to save the CI vector 
(multi;save,ref=XXXX.Y) 

then the output becomes:

 CI vector
 ---------

 20 20 20       0.9769517
 20 02 20      -0.1360810
 +- +- 20       0.0863966
 20 +- +-       0.0807951
 +- 20 +-      -0.0586269
 02 20 20      -0.0560267
 20 20 02      -0.0548366

 TOTAL ENERGIES                      -113.98318578

In particular, the 5th configuration in the second example doesn't even 
(seem to) appear in the first output at all.
Perhaps I don't properly understand how these CI vectors are to 
be read.  Is it something to do with CSFs vs Slater dets?

Confused,

Best regards
Tim


----
Tim Robinson
5n9 Department of Chemistry
University of Otago
64 3 479 5214