MOLPRO

18 ORBITAL LOCALIZATION 127
2.) Within each group of orbitals found for a given primary centre, those containing only
one centre (lone pairs) are included first. The remaining ones are ordered so that the
secondary atoms are in the order of centrelist. Orbitals with secondary centres which are
not in centrelist come last.
3.) If REVERT is given, the order in each localization group is reverted.
4.) If GROUP is given, only the orbitals in the given group are reordered. igrp is 2 for closed
shells and inactive orbitals, 1 for open-shells in single reference methods, and 3 for active
orbitals in CASSCF calculations.
5.) If THREIG is given, only orbitals with energies larger than the given value are reordered.
eps must be negative. The remaining orbitals come last (first if REVERT is given).
Note that core orbitals are neither localized nor reordered.
18.7.3 Defining reference orbitals (REFORB)
REFORB,record.file,specifications
The localized orbitals are reordered such that the overlap with the reference orbitals read from
record.file is maximized. This is useful for local correlation treatments for keeping the order of
the localized constant for different geometries. A state specific orbital set can be selected using
specifications, as explained in section 4.11.
18.7.4 Selecting the fock matrix (FOCK)
FOCK,record.file
This specifies a record holding a Fock operator to be used for ordering the orbitals. Note that
only SCF dump records hold fock operators. Default is the Fock operator from the energy
calculation which produced the input orbitals.
18.7.5 Selecting a density matrix (DENSITY)
DENSITY,record.file,specifications
This specifies a record holding a density matrix for construction of a fock operator used for
ordering the orbitals. This can be used if no fock operator is available, and has only an effect for
MCSCF localizations. By default, the (state averaged) MCSCF density is used. A state specific
density matrix can be selected using specifications as described in section 4.11.
18.8 Localization thresholds (THRESH)
THRESH,thresh,eorder
thresh is a threshold for localization (default 1.d-12). If eorder is nonzero (default 1.d-4), the
orbitals whose energy difference is smaller then eorder are considered to be degenerate and
reordered according to the position of their charge centres (see section 18.7).