MOPAC and charges

[CUNDARIT%MEMSTVX1.BITNET : at : OHSTVMA.ACS.OHIO-STATE.EDU]

 Fellow Netters,
         A colleague of mine is researching the metabolites of various
 psychoactive drugs using theory and experiments.  He is using MOPAC to
 compare the geometry of various metabolite structures, and from their
 electronic structure try to predict potential reactivity.  Since the
 most pertinent reactions are charge-controlled, he would like to know which
 of the various MOPAC Hamiltonians (AM1, PM3, MNDO) is most suitable for
 calculating Mulliken atomics charges.  Of course, there are philosophical
 problems with using the Mulliken versus the other schemes, but we want to
 keep it simple here.  I have seen much discussion about one of the MOPAC
 Hamiltonians giving spurious results for nitrogen compounds (which these
 molecules have), and I don't remember which, if any, was the offending
 culprit.  Thanks.
                                         Tom Cundari
                                         Assistant Professor
                                         Department of Chemistry
                                         Memphis State University
                                         Memphis, TN 38152