MOLPRO

4 GENERAL PROGRAM STRUCTURE 19
is given after the variable definition, the values of the variables are replaced by the values given
on the WF directive. Vice versa, if a variable definition follows a gobal WF directive, the new
value of the variable is used in the following. Note that WF input cards in command blocks have
preference over global WF directives or input variables.
4.10 Defining orbital subspaces
In the SCF, MCSCF, and CI programs it may be necessary to specify how many orbitals in each
symmetry are occupied (or internal in CI), and which of these are core or closed shell (doubly
occupied in all CSFs). This information is provided on the OCC, CORE, and CLOSED cards in
the following way:
OCC,m 1 ,m 2 ,...,m 8 ; CORE,co 1 ,co 2 ,...,co 8 ; CLOSED,cl 1 ,cl 2 ,...,cl 8 ; FROZEN, f r 1 , f r 2 ,..., f r 8 ;
where m i is the number of occupied orbitals (including core/frozen and closed), co i the number
of core orbitals, and cl i is the number of closed-shell orbitals (including the core orbitals) in the
irreducible representation i. In general, m i ≥ cl i , and cl i ≥ co i . It is assumed that these numbers
refer to the first orbitals in each irrep. FROZEN only exists in the MCSCF program and denotes
frozen core orbitals that are not optimized (note that in older MOLPRO versions frozen core
orbitals were denoted CORE).
Note that the OCC and CLOSED cards have slightly different meanings in the SCF, MCSCF and
CI or CCSD programs. In SCF and MCSCF, occupied orbitals are those which occur in any
of the CSFs. In electron correlation methods (CI, MPn, CCSD etc), however, OCC denotes the
orbitals which are occupied in any of the reference CSFs. In the MCSCF, FROZEN orbitals
are doubly occupied in all CSFs and frozen (not optimized), while closed denotes all doubly
occupied orbitals (frozen plus optimized). In the CI and CCSD programs, core orbitals are
those which are not correlated and closed orbitals are those which are doubly occupied in all
reference CSFs.
OCC, CORE and CLOSED directives are generally required in each program module where they
are relevant; however, the program remembers the most recently used values, and so the directives
may be omitted if the orbital spaces are not to be changed from their previous values.
Note that this information is also preserved across restarts. Note also, as with the WF information,
sensible defaults are assumed for these orbital spaces. For full details, see the appropriate
program description.
The orbital spaces may also be defined outside command blocks, and then the directive is treated
as global, i.e., it is used in all subsequent programs. Spaces specific to certain wavefunction
types can be defined by specifiying the program name with a CONTEXT option, e.g.,
OCC,4,2,1,CONTEXT=MULTI
Alternatively, the context can be appended to the directive name with an underscore. For example
OCC MULTI,4,2,1
is equivalent to the previous form.
Local input given within command blocks has preference over global input.
4.11 Selecting orbitals and density matrices (ORBITAL, DENSITY)
As outlined in section 4.3, the information for each SCF or MCSCF calculation is stored in
a dump record. Dump records contain orbitals, density matrices, orbital energies, occupa-