Quacpac TK 1.6.0

New features

• 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.

Bug fixes

• 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.