Subject: CCL:Re: Computational Chemist vs Theoretical Chemist

From: "Prof. Robert Topper" <[email-masked]>
Date: Mon, 29 Mar 1999 11:41:29 -0500 (EST)

Hello all

I think Stefan's got it just right (especially about the need
to have a sense of humor!). 

I was trained as a theoretical chemist. To me, what this means
is that I was trained to push a pencil with the goal of developing
certain mathematical aspects of chemistry. This includes making
theoretical improvements to transition-state theory, developing
new quantum path-integral representations, inventing a new theory
of the liquid state, working out better ways to set up
the integrals for 5th-order perturbation theory, and so forth.

Of course, I eventually use computers to implement all of the above.
But experimentalists use computers too. IMHO, 
this may also justifiably be called "computational chemistry"
(I know, not everyone agrees, this is an old debate, just my $0.02,
sincere apologies to all who find my heresy distasteful).

Novices tend to divide science into theory and
experiment, and therefore "computation must be theory."
As Stefan mentions, this is a historical bias.
Although computer simulation work is not experiment,
it isn't exactly theory either. When I was a student we used to
call computer simulations "numerical experiments" (these
days, maybe "virtual experiments" would be trendier), which
could be tested either against theory or experiment.

In Einstein's day things were different, but science now consists of
theory, experiment and simulation. Some people work in one, two or
even all three of these areas (I myself get into the lab once in
a blue moon).

So am I a theoretical physical chemist? A computational chemist?
A chemical physicist? A computational molecular thermodynamicist? 
Personally, I don't think of myself as any of the above.
I'm a chemist. 

*****************************************************************************
Robert Q. Topper                        email:   [email-masked]
Department of Chemistry                 phone:   (212) 353-4378
School of Engineering                   fax:     (212) 353-4341
The Cooper Union                        subway:  take the 6 to Astor Place
51 Astor Place                                   or the N/R to 8th street
New York, NY 10003                               and you're there!
*****************************************************************************
                 http://www.cooper.edu/engineering/chemechem/
*****************************************************************************

---

From: Richard Wood <[email-masked]>
Date: Mon, 29 Mar 1999 14:46:30 +36000

Dr. Topper-
    While I agree with you when you say "I am a chemist", as I have 
several years of experience working in the IR/CD area, as well as three 
plus years of experience doing MD simulations, I must disagree with you 
when you imply that the distinction between being a "theoretical chemist" 
vs. a "computational chemist" doesn't matter.  It matters to me (however, 
don't think that I lose sleep over it) because to me developing a theory 
and using it are two ENTIRELY different things.  I think that most any 
chemist can USE a theory; only a special "bird" can develop theory.  

    Let me give you an example.  A few years back, I was measuring IR/CD 
spectra of some (chiral) tetrasubstituted biphenyls, and also attempting to 
calculate the observed IR/CD spectra by varying the angle between the two 
rings (in other words, trying to find the angle that gave me the closest 
match with my experimental results).  We were using a simple coupled 
oscillator model to calculate the spectra, and my calculations of the 
spectra were too small, regardless of what angle I picked.  I then came 
to the conclusion that the distance between the too dipoles was too 
small, and thus R+ and R- were cancelling out, decreasing their 
magnitude.  I also concluded that my theory needed some modification.  
Lacking the necessary theoretical "ability", my project basically crashed 
and burned.  I guess that you are probably aware being a physical 
chemist, that if you are going to try and publish experimental results, 
you better have very good agreement between experiment and calculations.

Richard

On Mon, 29 Mar 1999, Prof. Robert Topper wrote:

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