The default AM1BCC charge model OECharges.AM1BCC
now lightly restrains the AM1 geometry
optimization to the starting coordinates. This allows the important relaxation
of bond and angle degrees of freedom while greatly reducing the potential to
alter the molecule’s conformation away from its starting coordinates. AM1
geometry optimization can be suppressed with
OECharges.AM1BCCSPt
or OECharges.AM1BCCNoSymSPt.
The AM1BCC charge models OECharges.AM1BCCSym and
OECharges.AM1BCCSPt
now symmetrize the partial charges
over bond-topologically equivalent atoms, e.g. methyl hydrogens, in keeping
with the original model. This is especially important with conformationally
flexible molecules. This behavior can be suppressed by using the default
OECharges.AM1BCC or the non-default models
OECharges.AM1BCCNoSym or
OECharges.AM1BCCNoSymSPt.