Subject: Geometry Optimization of a large Silicon cluster

From: "Cherif F. Matta" <[email-masked]>
Date: Fri, 28 Jun 2002 08:33:29 -0400 (EDT)

Dear CCLers,

I would very much appreciate any tip from you about the following
question:

I am trying to optimize quite a large silicon cluster (67 Si atoms + 
46 H atoms) representing the Si(111) 7x7 reconstructed surface.  

I have a lot of problems optimizing it even using the modest RHF/3-21G.  
What would be the best ECP that I can use to speed up this calculation 
and bring it to the realm of possibility? Are the geometies 
optimized using ECPs known to be good and reproduce experimental 
geometries?

Any other suggestions would be highly appreciated.

Thank you very much.  (I will summarize).

    Cherif
    
  ----------------------------------
  Chérif F. Matta,
  Theoretical/Computational Chemist,
  Polanyi Research Group,
  Lash Miller Chemical Laboratories,
  Chemistry Department,
  University of Toronto,
  80 St. George Street (Room 261),
  Toronto, Ontario, Canada M5S 1A1.
  ...................................
  Telephone:      (416) 978 - 3625
  Cellular:       (416) 996 - 2444
  Fax:            (416) 978 - 7580
  http://chem.utoronto.ca/~cmatta/
  -----------------------------------