Subject: Re: CCL:Seeing molecular orbitals?

From: "Rajarshi Guha" <[email-masked]>
Date: Mon, 3 Jul 2000 11:19:30 +0530

> other. I think molecules are the beautiful building blocks of our Universe
> and created for a purpose. I decline the view molecules are just chance
> particles. I suspect from my reading of CCL, my intention may be seen as

Hi,
    your comment suggests that somebody / something is making molecules to
satisfy some aestheic urge. I fully agree that molecules are beutiful (in
fact the shapes of organic molecules is what attracted me to chemistry when
I was entering high school) - but I also think that they just happen to be
beutiful. When you say that they are chance particles do you mean that they
*just exist* ? I don't think so. Most things in the universe have a function
to perform and they are made such that they perform it well - evolution. And
so it also applies to molecules. In the case of molecules, performance for a
function is not the only criterion - a more important (I think *most*) is
geometry constraints - the molecule is what it is becuase of the way the
bonds have to join! If it happens that this makes the molecule beautiful
then be it - in th end you'll have to work the numbers and data that arise
>from a molecule. Of course there should be a goal in the measurement and
calculation of these data - measurement for measurementas sake is not very
useful I think.

At the same time somebody has to document the data - it might seem a
pointless job, but when the data is put to use, the documenter will be able
to sit back with a smile of satisfaction.

In the end I think computational chemistry involves both kinds of work -
getting, verifying and using data. In the midst of all this good looking
molecules ;) makes the work fun!

Bye,
==================================
Rajarshi Guha
Dept Of Chemistry
IIT Kharagpur

Email : [email-masked]
Web  : www.psynet.net/jijog
==================================

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From: "Jens Spanget-Larsen" <[email-masked]>
Date: Fri, 21 Jul 2000 10:06:37 +0100

Henry Pang:

> I am new to computational chemistry. My background is medicine and human
> ecology in Australia. Your post is the first indicator I have seen over a wide
> range of CCL and books which signals caution. I am overwhelmed by the volume
> and intensity of work on the methodology and mensuration of molecules, as if
> that were the end in itself. No where do I see any concern for a Philosophy of
> Computational Chemistry, which addresses just what is computational chemistry
> and what its purpose might be in our Universe. I cannot believe the objective
> is merely to measure everything and simply document these data?
> 
> Even at my early stage, I am seriously pondering writing material jointly with
> my academic supervisor who is a computational chemist, which sets out the link
> (as I see it) between cosmology, quantum theory, relativity and higher
> dimensions theory on the one hand and computational chemistry on the other. I
> think molecules are the beautiful building blocks of our Universe and created
> for a purpose. I decline the view molecules are just chance particles. I
> suspect from my reading of CCL, my intention may be seen as revolutionary if
> not outrageous and could well cause an uproar?

Dear Henry,

thank you for your comments. However, my little message "Seeing molecular 
orbitals?" was not intended to be highly philosophical. - The "molecular 
orbital" is a model concept, a one-electron wavefunction which serves as a 
convenient building block in the description of molecular many-electron states, 
but it is not an "observable" in the physical, quantum mechanical sense.  In 
the molecular orbital approximation, the instantaneous correlation of the 
movements of the individual electrons is neglected; the electrons are allowed 
to "feel" each other only in an average manner.  Hence, per definition, the 
molecular orbital has no "physical existence", no matter what you imply by the 
word 'existence'.

Yours, Jens >--< 
                             
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JENS SPANGET-LARSEN         Phone:  +45 4674 2000  (RUC)
Department of Chemistry             +45 4674 2710  (direct)
Roskilde University (RUC)   Fax:    +45 4674 3011 
P.O.Box 260                 E-Mail: [email-masked]
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