MCSCF with arbitrary selected configuration spaces can also be performed. The only restriction is that always all CSFs with different spin couplings arising from the same orbital occupancy are included. There are two ways to select configurations. Either, they are selected from a previous calculation with a threshold, or they are defined explicitly in the input. Here we only describe the latter case; for more details please refer to the reference manual.
The configuration input starts with the select directive, and subsequently each orbital configuration is given by one line starting with the keyword con, followed by the occupation numbers of the active orbitals. The following example shows an input for formaldehyde.
***,formaldehyde angstrom geometry= !define the nuclear coordinates C O , C , rco H1 , C , rch , O , hco H2 , C , rch , O , hco , H1 , 180
rco=1.182 Ang rch=1.102 Ang hco=122.1789 Degree
basis=vdz !Select basis set hf !Perform HF calculation mcscf !invoke MCSCF program closed,4,,1 !4a1 and 1b2 inactive orbitals occ,6,2,3 !6a1, 2b1, 3b2 occupied orbitals wf,16,1,0 !16 electrons, Symmetry 1 (A1), singlet select !start configuration selection con, 3.1,-3.1,1.2,-1.2,1.3,-1.3 !occupied orbitals in 1st configuration con, 3.1,-3.1,2.2,-2.2,1.3,-1.3 con, 3.1,-3.1,1.2,-1.2,2.3,-2.3 con, 3.1,4.1,1.2,2.2,1.3,-1.3 con, 3.1,-3.1,1.2,2.2,1.3,2.3 con, 4.1,-4.1,1.2,-1.2,1.3,-1.3
This calculation includes all CSFs of the CASSCF with coefficients larger than 0.04.
molpro@molpro.net 2012-02-11