Eric Scerri, The Periodic Table, Its Story and Its Significance, = Oxford University Press, 2007

http://www.oup.com/us/catalog/general/subject/Ch= emistry/?view=3Dusa&ci=3D9780195305739

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= --Apple-Mail-27-853188524-- From owner-chemistry@ccl.net Fri Oct 29 23:11:00 2010 From: "N. Sukumar nagams%x%rpi.edu" To: CCL Subject: CCL: question on Born-Oppenheimer approx. Message-Id: <-43038-101029230855-22986-OIx7Prv3tRih/ECs50966w[#]server.ccl.net> X-Original-From: "N. Sukumar" Content-Disposition: inline Content-Transfer-Encoding: binary Content-Type: text/plain Date: Fri, 29 Oct 2010 23:09:10 -0400 MIME-Version: 1.0 Sent to CCL by: "N. Sukumar" [nagams^_^rpi.edu] I would say that the question of THE inherent structure is ill-defined (unless you care to specify what you mean). Do you mean the lowest total energy state of a specified number of electrons and specified nuclei? Or do you mean the lowest energy structure of a specified 2D formula (such as C2H5OH or CH3OCH3) or 2D structure? Or do you mean the most probable instantaneous configuration at a given temperature? In general, there are Born-Oppenheimer-like structures that can be thought of as being preferentially populated in a statistical ensemble at a given temperature. (C2H5OH and CH3OCH3 only share the same total single-molecule Hamiltonian). Dr. N. Sukumar Rensselaer Exploratory Center for Cheminformatics Research http://reccr.chem.rpi.edu/ -------------------------- "It is nice to know that the computer understands the problem. But I would like to understand it too." -- Eugene P. Wigner ==============Original message text=============== On Fri, 29 Oct 2010 20:20:33 EDT "Eric Scerri scerri.:.chem.ucla.edu" wrote: Dear CCL'ers For many years now a few theoretical chemists (Primas, Woolley, Sutcliffe) have claimed that there is something significant going on in connection with the Born-Oppenheimer approximation. They claim that applying the approximation amounts to writing the structure of a molecule in 'by hand' rather than the structure being inherent in the quantum formalism. They cite examples such as C2H5OH and CH3OCH3 which share the same Hamiltonian and conclude that structure cannot therefore be deduced > from QM in an ab initio fashion. Some philosophers of chemistry have taken this a good deal further as a sign that chemistry (molecular structure) cannot be strictly reduced to quantum mechanics. Some even claim that there is 'emergence' taking place. Most chemists I have discussed this issue with claim that these philosophers and even the theoretical chemists mentioned above are reaching incorrect conclusions. Most chemists claim that structure does really exist as a matter of fact and that we could in principle solve the Schrodinger equation without fixing the position of the nuclei by solving the equation for every conceivable arrangement and would thereby recover the inherent structure. I would be interested in comments and have a follow-up question if there is any interest in this topic. all the best, eric scerri Eric Scerri, The Periodic Table, Its Story and Its Significance, Oxford University Press, 2007 http://www.oup.com/us/catalog/general/subject/Chemistry/?view=usa&ci=9780195305739 ===========End of original message text===========