20.12 Examples

The simplest input for a CASSCF calculation for H$_2$O, $C_{2v}$ symmetry, is simply:

Input: h2o_casscf.com

Output: h2o_casscf.out

This could be extended, for instance, by the following input cards

OCC,4,1,2;       !  specify occupied space
CLOSED,2         !  specify closed-shell (inactive) orbitals
CORE,1;          !  specify frozen core orbitals
WF,10,1;         !  define wavefunction symmetry
START,2100.2;    !  read guess orbitals from record 2100, file 2 
ORBITAL,2140.2;  !  save final orbitals to record 2140, file 2
NATORB,PRINT,CI  !  print natural orbitals and diagonalize the hamiltonian
                 !  for the natural orbitals. The largest CI coefficients
                 !  are printed.

Example for a state-averaged calculation for CN, $X$ and $B$ $^2\Sigma^+$ states, and $A$ $^2\Pi_x$, $^2\Pi_y$ states averaged. A full valence CASSCF calculation is performed

Input: cn_sa_casscf.com

Output: cn_sa_casscf.out

Example for an RASSCF (restricted active space) calculation for N$_2$, including SCF determinant plus all double excitations into valence orbitals. The single excitations are excluded. $D_{2h}$ symmetry, CSF method used:

Input: n2_rasscf.com

Output: n2_rasscf.out