MOLPRO

19 THE MCSCF PROGRAM MULTI 147
19.12 Examples
The simplest input for a CASSCF calculation for H 2 O, C 2v symmetry, is simply:
geometry={o;h1,o,r;h2,o,r,h1,theta} !Z-matrix geometry input
r=1 ang !bond length
theta=104
!bond angle
hf
!do scf calculation
multi
!do full valence casscf
http://www.molpro.net/info/current/examples/h2o_casscf.com
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
FROZEN,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 Σ + states, and A 2 Π x , 2 Π y states
averaged. A full valence CASSCF calculation is performed
***,cn
r=2.2
geometry={c;n,c,r}
{rhf;occ,5,1,1;wf,13,1,1;
orbital,2100.2}
!define bond length
!RHF calculation for sigma state
!save orbitals to record 2100.2 (default)
{multi;occ,6,2,2;closed,2;
!Define active and inactive orbitals
start,2100.2;
!Start with RHF orbitals from above
save,ref=4000.2 !Save configuration weights for CI in record 4000.2
wf,13,1,1;state,2;wf,13,2,1;wf,13,3,1;!Define the four states
natorb,ci,print;
!Print natural orbitals and associated ci-coefficients
tran,lz
!Compute matrix elements over LZ
expec2,lzz}
!compute expectation values for LZZ
http://www.molpro.net/info/current/examples/cn_sa_casscf.com
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: