RE: Qeq & others charge equilibration method

 > I currently need a very fast method to estimate the molecular
 > electrostatic potential outside de Van der Waals surface, preferably
 > avoiding QM calculations, and turn to empirical charge equilibrations
 > methods. Finally I consider using the QEq scheme, but maybe I could
 > benefit from the experience of some of us, especially if s.O. already
 > studied MEP built from QEq charges ??
 >
 A simple idea I've been toying with is the use of Rappe's QEq scheme
 (perhaps coupled with Landis' VALBOND scheme) together with a
 variationally derived analytical Thomas-Fermi expression for the charge
 density of charged atoms.  This generates a very quick, crude, but
 surprisingly good electron density (a superposition of charged atom
 densities) and a full electrostatic potential (in analytical form)
 corresponding to the QEq charges.  It's fast enough to perform at an MD
 timescale.
 - Jack
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  Jack A. Smith             ||
  Union Carbide             || Phone:  (304) 747-5797
  Catalyst Skill Center     || FAX:    (304) 747-4672
  P.O. Box 8361             ||
  S. Charleston, WV  25303  || smithja #*at*# ucarb.com
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