SCFCRT sets the self-consistent field criterion, i.e., the change in
energy in kcal/mol on two successive iterations. For most situations where the
SCF criterion need to be modified, use RELSCF instead. RELSCF
is useful if the value of the default SCF criterion is not readily available, as for example
when PRECISE or any
other keywords that modify the SCF criterion is used.
The default SCF criterion,1x10-4 kcal/mol, is to be replaced by that defined by
SCFCRT=n.nnn. Other criteria may make the requirements
for an SCF slightly more stringent. The SCF criterion can be varied from
about 1.0 to 1.D-25, although numbers in the range 0.1 to 1.D-9 will
suffice for most applications.
NLLSQ, SIGMA, or
TS calculations, the default value of SCFCRT is 1x10-7.
Be careful in FORCE calculations - high precision is needed, if high precision
is not used, the vibrational frequencies might be wrongly predicted.
An overly tight criterion can lead to failure to achieve an SCF, and
the consequent failure of the run. See also
RELSCF and PRECISE