MOLPRO

4 GENERAL PROGRAM STRUCTURE 20
tion numbers, fock matrices and other information as wavefunction symmetries etc. Subsequent
calculation can access the orbitals and density matrices from a particular record using the
ORBITAL and DENSITY directives, respectively. These input cards have the same structure in
all programs. The general format of the ORBITAL and DENSITY directives is as follows.
ORBITAL[,[RECORD=]record] [,[TYPE=]orbtype] [,STATE=state] [,SYM[METRY]=symmetry]
[,SPIN=spin] [,MS2=ms2] [,[N]ELEC=nelec] [,SET=iset] [,OVL] [,NOCHECK] [,IGNORE[ ERROR]]
DENSITY[,[RECORD=]record] [,[TYPE=]dentype] [,STATE=state] [,SYM[METRY]=symmetry]
[,SPIN=spin] [,MS2=ms2] [,[N]ELEC=nelec] [,SET=iset]
where the (optional) specifications can be used to select specific orbitals, if several different
orbital sets are stored in the same record. The meaning of the individual specifications are as
follows:
orbtype
Orbital type. This can be one of
CANONICAL: canonical or pseudo-canonical orbitals;
NATURAL: natural orbitals;
LOCAL: localized orbitals;
LOCAL(PM): localized Pipek-Mezey orbitals;
LOCAL(BOYS): localized Boys orbitals;
PROJECTED: projected virtual orbitals used in local calculations.
Without further specification, the most recently computed orbitals of
the specified type are used. If the orbital type is not specified, the
program will try to find the most suitable orbitals automatically. For
instance, in MRCI calculations NATURAL orbitals will be used preferentially
if available; MRPT (CASPT2) calculations will first search
for CANONICAL orbitals, and local calculations will first look for
LOCAL orbitals. Therefore, in most cases the orbital type needs not
to be specified.
state Specifies a particular state in the form istate.isym. For instance, 2.1
refers to the second state in symmetry 1. This can be used if density
matrices or natural orbitals have been computed for different states in
a state-averaged CASSCF calculation. If not given, the state-averaged
orbitals are used. The specification of isym is optional; it can also be
defined using the SYMMETRY key.
dentype
symmetry
spin
ms2
nelec
iset
Density type. This can be one of
CHARGE: charge density;
SPIN: UHF spin density;
TRANSITION: transition density matrix;
The default is CHARGE.
Specifies a particular state symmetry. Alternatively, the state symmetry
can be specified using STATE (see above).
Spin quantum number, i.e. 0 for singlet, 1/2 for doublet, 1 for triplet,
etc. Alternatively MS2 can be used.
2M S , i.e. 0 for singlet, 1 for doublet, 2 for triplet etc. Alternatively,
SPIN can be used.
Number of electrons.
Set number of orbitals. The orbital sets are numbered in the order they
are stored.