Subject: orbitals

From: Eric Scerri <scerri.-at-.chem.ucla.edu>
Date: Wed, 28 May 2003 09:30:51 -0700

It seems to me that paper [1] at least makes the elementary 
philosophical error of claiming that if something is useful then it 
must have physical reality.

Stowasser and Hoffmann say virtually as much in this article.

Many scientific concepts have proved useful in the history of science 
but were eventually found to be redundant or non-existent.  For 
example, caloric, phlogiston, the ether etc.

But is there a sense in which the Kohn-Sham orbitals are "more real" 
than the orbitals used in ab initio work?  This seems to be the claim 
of some recent authors.

But then we get into another odd notion, namely that having physical 
reality comes in degrees!

please see,

The Recently Claimed Observation of Atomic Orbitals and Some Related 
Philosophical Issues", Philosophy of Science, 68,(Proceedings) 
S76-S88, N. Koertge, ed. Philosophy of Science Association, East 
Lansing, MI, (2001)

Have Orbitals Really Been Observed?, Journal of Chemical Education, 
77, 1492-1494, (2000)

although neither of these articles discuss the reality of orbitals of 
the DFT variety.

regards,
eric scerri

I would like to invite contibutions of articles or comments on this 
question to the journal Foundations of Chemistry (see below for info).

----------

>  On Tue, 27 May 2003, Jens Spanget-Larsen wrote:
>>
>>  > And in principle, MOs are not physical quantities; they are model
>>  > constructions, and as such they have no physical reality and they
>>  > cannot be observed experimentally.
>>
>>  Well, there is a lot of discussion in the literature on this topic.
>>  A few good examples, biased towards my thinking, could be:
>>
>>  [1] Stowasser and Hoffmann, "What Do the Kohn-Sham Orbitals and
>>      Eigenvalues Mean?", J.Am.Chem.Soc. 121 (1999) 3414-3420.
>>  [2] Baerends, Theor.Chem.Acc. 103 (2000) 265-269.
>
-- 

Dr. Eric Scerri ,
UCLA,
Department of Chemistry & Biochemistry,
607 Charles E. Young Drive East,
Los Angeles,  CA 90095-1569
USA

E-mail :   scerri.-at-.chem.ucla.edu
tel:  310 206 7443
fax:  310 206 2061
Web Page:    http://www.chem.ucla.edu/dept/Faculty/scerri/index.html

Editor  of  Foundations of Chemistry
http://www.kluweronline.com/issn/1386-4238

Also see International Society for the Philosophy of Chemistry
http://www.georgetown.edu/earleyj/ISPC.html