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

[H. -J. Werner]

In the first case, the program uses Slater determinants as a basis,
which is the default. In this case, (-) means beta spin and (+) alpha
spin. If you save the reference vector for later use in mrci, CSFs 
have to be used, and the program automatically switches to this 
(same as giving the CONFIG directive). In this case, a genealogical spin 
coupling scheme is used, and +/- corresponds to going up or down in 
the branching diagram (to be read from left to right). 
Joachim Werner
----- Forwarded message from Tim Robinson <tim at loki.otago.ac.nz> -----

From: Tim Robinson <tim at loki.otago.ac.nz>
To: molpro-user at molpro.net
Subject: [molpro-user] CI vector: the role of the observer (?)
Date: Thu, 10 Jun 2004 15:12:34 +1200 (NZST)
Message-ID: <Pine.LNX.4.44.0406101241160.27693-100000 at loki.otago.ac.nz>

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

----- End forwarded message -----

-- 
Prof. Hans-Joachim Werner
Institute for Theoretical Chemistry
University of Stuttgart
Pfaffenwaldring 55
D-70569 Stuttgart, Germany
Tel.: (0049) 711 / 685 4400
Fax.: (0049) 711 / 685 4442
e-mail: werner at theochem.uni-stuttgart.de