About "Config" keyword (fwd)

[H.-J. Werner]

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