About "Config" keyword (fwd)

[John Kerkines]

Dear Prof. Werner (and listmembers),

Thank you for your reply. This is not what I am asking though. I would
like to know how to correctly READ the CI vector when using CSFs. For
instance, in the example I have mentioned in my initial message (see
below), when using determinants I read:

++ - +       0.1704248

as "1a1(alpha)2a1(alpha)1b1(beta)1b2(alpha)".

When using CSFs, the same line is:

++ - +       0.2783026

This corresponds to one spin-adapted linear combination, isn't it? 
Which one is it? And which one is, for instance: 
"+- + +       0.0000000"?

Ioannis Kerkines


On Thu, 6 Sep 2001, H.-J. Werner wrote:

> Hi,
> one can only specify "orbital configurations", i.e., the occupancy
> for each orbital. The program will then generate all possible
> spin-adapted CSFs. It is not possible to use subsets of CSFs
> for a given orbital configuration. The input for your example
> would read
> 
> select
> con,2,0,1,1
> con,0,2,1,1
> con,1,1,1,1
> 
> but in fact this would generate all possible CSFs for 3Sig-.
> 
> Note that determinants can only be used for CASSCF but not
> for selected MCSCF (the select card triggers the use of CSFs).
> Also note that the closed-shell (inactive) orbitals are not
> included on the con cards as shown above.
> 
> Instead of the orbital occupation numbers, one can also
> specify the orbitals itself, see e.g., 
> 
> testjobs/h2o_explicit.test
> testjobs/o3_explicit.test
> 
> and the manual.
> 
> H.-J. Werner
> 
> > 
> > Hello,
> > 
> > I am really puzzled by the use of the "Config" keyword in CASSCF
> > calculations. It is supposed to work with CSFs instead of Slater
> > determinants. I cannot understand how to read the CI vector in the case of
> > CSFs. For example, a single point CASSCF (4,4) triplet sigma minus
> > calculation 1st with determinants and 2nd with CSFs produces the
> > following
> > output:
> > 
> >  CI vector
> >  ---------
> > 
> >  20 + +       0.8726238
> >  02 + +      -0.3497846
> >  -+ + +      -0.1704248
> >  ++ - +       0.1704248
> >  ++ + -       0.1704248
> >  +- + +      -0.1704248
> > 
> >  TOTAL ENERGIES                     -1815.56889064
> > 
> > 
> >  CI vector
> >  ---------
> > 
> >  20 + +       0.8726238
> >  02 + +      -0.3497846
> >  ++ - +       0.2783026
> >  ++ + -       0.1967896
> >  +- + +       0.0000000
> > 
> >  TOTAL ENERGIES                     -1815.56889064
> > 
> > 
> > I can easily understand why there is a difference in coefficients between
> > CSFs and determinants, but how does one read for instance "++ - +" in the
> > CSF case? How does one know to which spin-adapted linear combination does
> > it belong to? What is the convention, since "++ - +" is written in both
> > cases?
> > 
> > Best Regards
> > Ioannis Kerkines
> > 
> > 
> 
> 
> --
> Prof. Hans-Joachim Werner
> Institute for Theoretical Chemistry
> University of Stuttgart
> Pfaffenwaldring 55
> D-70569 Stuttgart
> Tel: (0049) 711 / 685 4400
> Fax: (0049) 711 / 685 4442
> email: werner at theochem.uni-stuttgart.de
>