Xref: utzoo sci.physics:3285 sci.misc:1402 sci.research:366
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From: colvin@mozart.llnl.gov (Mike Colvin)
Newsgroups: sci.physics,sci.misc,sci.research
Subject: Re: atomic simulation software ...
Message-ID: <6567@lll-winken.llnl.gov>
Date: 28 Apr 88 18:27:06 GMT
References: <203@heurikon.UUCP> <4864@cup.portal.com>
Sender: usenet@lll-winken.llnl.gov
Reply-To: colvin@mozart.llnl.gov.UUCP (Mike Colvin)
Organization: Lawrence Livermore National Laboratory
Lines: 29

In article <4864@cup.portal.com> doug-merritt@cup.portal.com writes:
>
>In general, chemistry is an empirical field *aided* by narrow applications
>of quantum mechanics. There is currently no hope of predicting general
>chemical properties wholly from first principles.

  Actually this is not entirely correct.  There is now a growing field 
of chemistry known as ab initio quantum chemistry that involves the
numerical solution of the molecular Schrodinger equation to calculate
chemical properties.  Of course these methods yield only approximate
solutions, but currently it is possible to predict molecular structures
to within about %1 (bond lengths and angles) and energy differences
to comparable accuracy.  It is possible to use these methods to calculate
almost any well-defined chemical property, including dipole moments,
vibrational frequencies, etc.  Note that although the methods are
approximate, they are entirely from first principles, no empirical data
is used.  In principle these methods are usable for molecules
of arbitrary size, but since even the lowest accuracy method (self-consistant
field) has complexity  0(n**4) where n is approx. the # electrons, these
methods are limited to molecules with a few dozen electrons.  

  The are a variety of ab initio quantum chemistry packages that have been developed by different research groups around the country.  (Big wheels in
the field include John Pople at Carnegie Mellon, Henry F. Schaefer at
U.C. Berkeley (was my Ph.D. advisor), and Bill Goddard at Cal. Tech. )
Currently, only John Pople is freely distributing his package (called 
Gaussian 86).  It is available for a nominal distribution fee. I recommend 
calling his research group at Carnegie Mellon if you would like a copy.

   - Mike Colvin  (colvin@mozart.llnl.gov)