PM3 Charges

From: Andy Holder <AHOLDER \\at// VAX1.UMKC.EDU>
Subject: PM3 Charges
Date: Sun, 1 Dec 1991 08:19 CDT
Charges with PM3 are traditionally suspect and has been noted before.
   The problems with charge inversion (as you describe with nitrogen)
   are especially severe.  The basis of this problem is a chemically
   poor set of parameters that are corrected by some rather extreme
   Gaussian functions.  The reliability of AM1 as compared with much
   more advanced methods in charge prediction has been illustrated rep-
   eatedly.  If charges (and other electronic properties for that
   matter) interest you, I would recommend sticking with AM1.
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                               DR. ANDREW HOLDER
 Department of Chemistry              ||  BITNET Addr:   AHOLDER \\at// UMKCVAX1
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