MOLPRO

32 THE FULL CI PROGRAM 244
32 THE FULL CI PROGRAM
This module is the determinant full CI program, as described in
P.J. Knowles and N.C. Handy, Chem. Phys. Letters 111 (1984) 315,
P.J. Knowles and N.C. Handy, Comp. Phys. Commun. 54 (1989) 75.
Published work resulting from the use of this program should cite these references.
The program in normal use finds the lowest eigenvector of the complete CI hamiltonian matrix;
more sophisticated use is possible, but not documented here. The program is interfaced to free
standing versions such as supplied in the CPC program library by use of the DUMP option.
The program is called with the command FCI.
32.1 Defining the orbitals
ORBIT,name.file;
name.file specifies the record from which orbitals are read. The default is the set of orbitals from
the last SCF, MCSCF or CI calculation.
32.2 Occupied orbitals
OCC,n 1 ,n 2 ,...,n 8 ;
n i specifies numbers of occupied orbitals (including CORE) in irreducible representation number
i. If not given, the default is the complete basis set.
32.3 Frozen-core orbitals
CORE,n 1 ,n 2 ,...,n 8 ;
n i is the number of frozen-core orbitals in irrep number i. These orbitals are doubly occupied
in all configurations, i.e., not correlated. If no CORE card is given, the program uses the same
core orbitals as the last CI calculation; if there was none, then the atomic inner shells are taken
as core. To avoid this behaviour and correlate all electrons, specify
CORE
32.4 Defining the state symmetry
The number of electrons and the total symmetry of the wavefunction are specified on the WF
card:
WF,elec,sym,spin
where
elec:
sym:
spin:
is the number of electrons
is the number of the irreducible representation
defines the spin symmetry, spin= 2S (singlet=0, doublet=1, triplet=2,
etc.)