From chemistry-request@ccl.net Sun Nov 24 10:11:04 1991
Date: Sun, 24 Nov 1991 09:37 EST
From: CHAMH@INDSVAX1.INDSTATE.EDU
Subject: reaction field for non-spherical molecules
To: chemistry@ccl.net
Status: R

	With respect to the question about models to account for the
reaction field for non-spherical molecules, Myers and Birge (J. Chem.
Phys., 73, 5314 (1980)) considered this problem for a cylindrical
solvation cavity. As expected there is, in this case, an orientation
factor that affects the value of the dispersive interaction between
the transition dipole and the solvent medium.

Arthur M. Halpern
Department of Chemistry
Indiana State University
Terre Haute, IN  47809
BITNET  CHAMH@INDAVAX1


From chemistry-request@ccl.net Sun Nov 24 14:12:34 1991
From: fant@umbc3.umbc.edu (Andrew Fant)
Subject: Non-classical carbocations in Mopac
To: chemistry@ccl.net
Date: Sun, 24 Nov 91 13:43:35 EST
Status: R

     In the course of our current study on radialene chemistry, we have had 
the need to do structural minimizations on some protonated species that our
inuition tell us should be non-classical.  AM1 in Mopac 6.0 gave us a very 
classical structure that looked wrong, so we did a test case involving the
norbornadienyl cation.  That gave a classical carbocation and a Heat of
Formation over 20 kcal/mole too high, as compared to the NIST GIANT tables.

     My question is this:  Are Mopac and/or AM1 documented to be inaccurate
with non-classical carbocations?  I would appreciate any comments and 
references that anyone knows of.  If this is common computational folklore that
I have not come across before, my apologies for airing my ignorance in public.

Thank you in advance for your comments

+-----------------------------------------------------------------------------+
 Andy "The Fantom" Fant                    (fant@{umbc2,chem3,umbc4}.umbc.edu)
      Disclaimer: My postings are definitive, reality is often inaccurate
  "It is my supposition that the Universe is not only queerer than we imagine,
	It is queerer than we CAN imagine." - J.B.S. Haldane