MOLPRO

29 LOCAL CORRELATION TREATMENTS 212
THRCOR=thresh
Threshold for deleting projected core orbitals. The functions are only
deleted if their norm is smaller than thresh (default 0.1)
The thresholds can also be specified on the THRESH directive.
29.6 Options for selection of domains
The following sections describe the most important options which affect the domains.
29.6.1 Standard domains
Standard domains are always determined first. They are used to define strong, close, weak, and
distant pairs. More accurate results can be obtained with extended domains, as described in
section 29.6.2.
THRBP=value
CHGMIN=value
Threshold for selecting the atoms contributing to orbital domains using
the method of Boughton and Pulay (BP). As many atoms as needed
to fulfill the BP criterion are included in a domain. The order in which
atoms are considered depends on the parameter MAXBP, see below.
The default is THRBP=0.98. THRBP=1.0 includes all atoms into
each orbital domain, i.e., leads to full domains. If no pairs are neglected,
this should yield the canonical MP2 energy.
The criterion is somewhat basis dependent. See section 29.9.4 for
recommended values of this threshold.
determines the minimum allowed Mulliken (or Löwdin) charge for
an atom (except H) in a domain, i.e., atoms with a smaller (absolute)
charge are not included, even if the THRBP criterion is not fulfilled
(default 0.01).
CHGMINH=value as CHGMIN, but used for H-atoms (default 0.03).
CHGMAX=value
MAXBP=maxbp
MULLIKEN=option
MERGEDOM=number
If the atomic charge is larger than this value, the atom is included,
independent of any ranking.
If maxbp=1, the atoms are ranked according to their contribution to
the Boughton-Pulay overlap. If maxbp=0 (default), the atoms are
ranked according to atomic charges. In both cases atoms with charges
greater than CHGMAX are always included, and atoms with the same
charges are added as groups.
Determines the method to determine atomic charges. MULLIKEN=0
(default): squares of diagonal elements of S 1 2 C are used (Löwdin
charges); MULLIKEN=1: Mulliken gross charges are used. The first
choice is less basis set dependent and more reliable with diffuse basis
sets.
If number is greater than zero, all orbital domains containing number
or more atoms in common are merged (number=1 is treated as number=2,
default 0). This is particularly useful for geometry optimizations
of conjugated or aromatic systems like, e.g., benzene. In the latter
case, MERGEDOM=1 causes the generation of full π-domains, i.e.,
the domains for all three π-orbitals comprise all carbon basis functions.
Note that the merged domains are generated after the above