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From: M Dominic Ryan <ryanmd*- at -*mh.us.sbphrd.com>
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Date: Wed, 23 Feb 2000 09:58:03 -0500 (EST)
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To: Chemistry \\at// CCL.net
Subject: The "birth-year" of computational chemistry?

I dug into this question about 12 years ago.  It depends of course on just
what you call computational chemistry.  Does it have to be using a
computer?  I would argue that should not be a requirement.  Rather the
real underlying field is the construction of a numeric simulation that
represents 'reality' in a context that permits testing concepts and
thereby learning something.  Today we use computers in their current form,
perhaps this will change in the decades to come.

I point back to early spectroscopic work.  The earliest I think is work by
Andrews, in the 20s.  Once citation I have is in Physical Reviews, v36,
p531, 1930, Kettering, Shutts and Andrews (General Motors Corporation).
"A representation of the Dynamic Properties of Molecules by Mechanical
Models".  I think of this as the birth of molecular modeling.  They built
molecular models of things like toluene, benzene, chlorobenzene using
steel balls and calibrated springs.  They attached an oscillator and swept
the frequency.  They then used a strobe light an found the standing
waves.  In this way they mapped out a molecular mechanics model the IR and
Raman spectra.  They were then able to draw conclusions about the correct
molecular structure by doing the experiment on various bonding models of
benzene by having springs attached in different arrangements.  I think
they got it wrong in the end, but that sure looks like molecular mechanics
with an analog computer to me.

There is also the work by Urey and Bradley, whose names are still attached
to a force field, that begins around 1931 with a paper in Physical Review,
p1969, 1931 (apparently Bradley's Ph.D. thesis).  He discusses Andrew's
papers and also a paper I never saw by Bjerrum in physik. Ges. Ber.  v16,
p737, 1914, proposing those sorts of forces acting upon bonded atoms.  He
of course also cites Slater (1931) and Pauling JACS,v53,p1367, 1931, as
discussing the nature of the forces on a chemical bond.

Still later, I put Frank Westheimer (with John Mayer) at the birth of
computational chemistry using numerical methods.  He calculated an
activation energy for racemization of 2,2'-dibromo-4,4'-dicarboxydiphenyl
in J. Chemical Physics, v15, p252, 1947 (there is also an earlier paper
v14, p733,1946).  He used an exponential function to describe the rates
and pull out constants.

Other names at that time are T.L. Hill, J. Chem. Phys. v14,465 (1946)
and W. Gordy, J.Chem.Phys 14,305(1946).
__
M. Dominic Ryan   (610)-270-6529     SmithKline Beecham Pharmaceuticals 
Internet:  ryanmd;at;mh.us.sbphrd.com     King of Prussia, PA