Subject: SUMMARY: Potential parameter fitting

From: Keith Refson <[email-masked]>
Date: Fri, 17 Aug 2001 12:09:57 +0100

I received a few attempts to summarise the responses, so here is a
brief summary.

I asked what programs were avialable for potential parameter fitting
to energy hypersurfaces, such as ab-initio energies.  The main
responses were

1. NBP by the late Prof D. E. Williams, 
   http://www.louisville.edu/~dewill01/nbp.html

   This seems to be about the best suited program for such tasks.  
   It used to be obtainable directly from Prof Williams, but none of
   my respondents had any idea how to obtain it now, as he recently
   passed away. I hope this does not become lost to the community.

2. A number of respondents pointed me to GULP by Julian Gale
   http://www.ch.ic.ac.uk/gale/Research/gulp.html
   which is slightly embarrassing since I thought I knew that program
   fairly well :)  It can indeed be used to fit to an energy hypersurface
   (which I erroneously thought it wasn't well suited for).

   GULP uses a 3D periodic model, which isn't what I need for this
   particular calculation, (A simple isolated moecular cluster), but
   of course it's not to hard to achieve this by judicious use of a
   large supercell and interaction cutoffs and turning off the
   long-ranged part of coulomb interactions.

3. Though not what I was looking for Andrew Horsfield
   ([email-masked])suggested that The OXON tight binding
   package also fits (and implements) Tersoff type potentials.

4. "Kjeld Rasmussen studied with Lifson and has modified that august
   program over the years to be a parameter-fitting tool. It can fit to
   structural parameters and vibrational frequencies but i do not believe
   to a hypersurface. Kjeld readily gives the program away. Some of the
   background to his program is given at:
   [1]http://struktur.kemi.dtu.dk/cff/cffhome.html"

5. "Arnold Hagler had a similar program (I believe called "Probe") that
   also came from Lifson's program and it was modified to fit
   hypersurface data but I think it is now a proprietary commercial
   product for MSI consortium members."

6. Marcelo Zaldini has been "developing a methodology, called SJBR,
   to do the parametrization of the intermolecular terms (coulomb +
   lennard_jones), based upon ab initio calculations, in an automatic
   fashion." which he hopes to release at some future time, when it
   is finished. 

7. Other co-respondents recommended general least squares fitting
   methods such as the least-squares module in Scientific Python,
   available from
   http://dirac.cnrs-orleans.fr/programs/scientific.html,
   or even gnuplot!  Although of course the built-in fit is only
   1-dimensional and therefore not suitable, the gnuplot FAQ contains
   links to a number  of other general purpose leasy-squares programs,
   such as Fudgit.

   None of these really fulfil the spirit of my request which was for a
   program which handles the bookkeeping and set-up for molecular
   models.

Thanks to

Konrad Hinsen <[email-masked]>,
Manuel Melle-Franco <[email-masked]>,
Irena Efremenko <[email-masked]>,
Andrew Rohl <[email-masked]>,
Brian J. Teppen" <[email-masked]>,
Marcelo Zaldini Hernandes <[email-masked]>,
Daquan Gao <[email-masked]>
Andrew Horsfield <[email-masked]>

for the suggestions.

Keith Refson

-- 
Dr Keith Refson,        "Paradigm is a word too often used by those who would
Dept of Earth Sciences      like to have a new idea but cannot think of one." 
Parks Road,                  -- Mervyn King, Deputy Governor, Bank of England
Oxford OX1 3PR, UK        
Keith.Refson@                       Tel: 01865 272026
             earth.ox.ac.uk         Fax: 01865 272072