% 
% Example of state-averaged CASSCF for the C2 molecule
% see C. D. Sherrill and P. Piecuch, J. Chem. Phys. 122, 124104 (2005)
%

psi:(
  label = "c2"
  memory = (30.0 MB)
                                                                                
  charge = 0
  multp = 1

  ncasiter = 50
  wfn = casscf
  reference = rhf

  docc =            (2 0 0 0 0 2 1 1)
  restricted_docc = (1 0 0 0 0 1 0 0)
  active =          (2 0 1 1 0 2 1 1)
)

input: (
  basis = "6-31G*"
  units = angstrom
  zmat = (
    (c)
    (c 1 1.20)
  )
  origin = (0.0 0.0 0.0)
)

%
% This input also serves as an example of the filter guess capability
% of DETCI, which is for advanced users only.  Normal SA-CASSCF computations
% do not typically need the filter guess lines.
% 
% The filter guess stuff below is used to filter out the delta state
% of C2, which in the D2H computational subgroup appears as a 1A1 state
% just like the two sigma states we're interested in.  We only want the
% two lowest sigma states, so we filter out all CI roots that don't look
% like sigma states.  For a sigma state, the determinants (56 56) and
% (66 66) [see below] must appear with the same sign.  As shown in the
% output, these determinants are
%
%    1   -0.626186  (   66,   66)  2Ag X  3Ag X  2B1uX  1B3uX
%    2   -0.626186  (   56,   56)  2Ag X  3Ag X  2B1uX  1B2uX
%
% Of course the numbering (56 56) and (66 66) is particular to this
% calculation and phase relationships between determinants for particular
% states needs to be figured out by hand and checked vs a test calculation
% before the appropriate information can be input for a filter_guess
% calculation.  For more information see the article mentioned at the
% top of this file.
%

detci: (
  filter_guess = true
  filter_guess_sign = 1
  filter_guess_det1 = (56 56)
  filter_guess_det2 = (66 66)
  calc_ssq = true
  num_roots = 2
  average_states = (1 2)
)

