From owner-chemistry _-at-_)ccl.net  Fri Aug  4 10:16:17 1995
Received: from bioc1.biosym.com  for tony[ AT ]bioc1.biosym.com
	by www.ccl.net (8.6.10/930601.1506) id KAA11030; Fri, 4 Aug 1995 10:13:11 -0400
Received: from biosym.com by bioc1.biosym.com (5.64/0.0)
	id AA26956; Fri, 4 Aug 95 06:10:51 -0700
Received: by east1.biosym.com (920330.SGI/920502.SGI)
	for bioc1!ccl.net!chemistry-request id AA07441; Fri, 4 Aug 95 08:57:38 -0400
Date: Fri, 4 Aug 95 08:57:38 -0400
From: tony*- at -*bioc1.biosym.com (Tony Schmidt)
Message-Id: <9508041257.AA07441[ AT ]east1.biosym.com>
To: ccl.net!chemistry-request;at;bioc1.biosym.com
Subject: Re:  CCL:Question about Electrostatics in Molecular Mechanics
Cc: tony /at\biosym.com, chemistry /at\ccl.net


On Aug.8 Bill Welsh wrote:

Dear Netters,

Please help settle a small controversy.  For a particular molecular 
mechanics calculation, I derived partial atomic charges from bond 
dipole moment measurements made in nonpolar solvent.  I then ran 
molecular mechanics calculations using an in vacuo dielectric constant 
of 1.00.  A colleague argues that I must use a dielectric constant 
appropriate to the nonpolar solvent from which the charges were 
derived (e.g., 2-3).  It seems to me that the charges already embody 
the effect of the nonpolar solvent's dielectric constant, and so using 
the in vacuo value of 1.00 is okay and perhaps preferred.  Stated another 
way, it seems to me that using these charges AND the dielectric of 2-3 
would count the effect of the nonpolar solvent twice.

Any opinions on this matter are appreciated.

Thanks ...

Bill Welsh
Dept. of Chemistry
Univ. of Missouri-St. Louis
-----------------------------------------------------

If you have dipole moments in solvent, you may have to scale them for vacuum
using e.g. strategy by Sharp et al, J.Phys.Chem. 96, 3822 (1992).

Tony Schmidt
tony %-% at %-% biosym.com