Subject: Electrostatic model for ordinary hydrogen bonds

From: "Donald E. Williams" <[email-masked]>
Date: Tue, 19 May 1998 14:43:06 -0400

There seems to be a widespread misunderstanding that an ordinary
hydrogen bond (say O-H...O) can be modeled with a purely electrostatic
potential by "dumping everything into electrostatic parameters".  If anyone
knows of such a model, I would like to hear about it.
	There is a parameterization called the "disappearing hydrogen" model of
the OHB.  In this model, electrostatics are included, but also (and very
importantly) the repulsion of the hydrogen atom is set to zero, quite a drastic
change from a normal hydrogen atom.  It is easily shown that the effect of
eliminating hydrogen repulsion is by far more important than the
electrostatics.

>decompose an HB into its "electrostatic" and "covalent" contributions. An
>"ordinary" HB (OHB) has both electrostatic and covalent components, although
>it can be reasonably modelled by classical force fields by dumping everything
>into electrostatic parameters. An OHB can be neutral or charged. A charged

-Donald Williams

-- 
Dr. Donald E. Williams		email:[email-masked]
Department of Chemistry
University of Louisville	phone:502-852-5975
Louisville, KY 40292		fax:  502-852-8149