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                SEMINAR OF THE DYNAMICAL SYSTEMS GROUP
        Institute for Computational Sciences and Informatics
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      Cluster Model Theoretical Studies of Surface Properties  
                    Computation For Understanding

                            Paul S. Bagus 
                         Chemistry Division
                     National Science Foundation

The results of cluster model theoretical studies of chemical bonding 
and chemisorption at surfaces will be presented. In these studies, a 
finite, and often small, number of atoms are chosen to represent the 
semi-infinite surface of a crystal. The primary concern is for the 
chemical bond between the surface atoms and an atom or  molecule which 
is adsorbed on the surface. The clusters are treated as though they 
were chemical molecules and quantum mechanical electronic 
wavefunctions are calculated using molecular orbital theory. A unique 
advantage of this approach is that it provides a natural way to 
describe surface phenomena with traditional chemical terms and 
concepts. Large scale computations are required to obtain the cluster 
wavefunctions, especially as the number of atoms is increased to 
include effects from a larger portion of the surface. However, the 
focus will not be on the computational details but on analysis of the 
wavefunctions to relate concepts to observed properties. In 
particular, sometimes surprising consequences of traditional 
consequences like ionicity and steric repulsion will be described.

                      Monday , November 14 1994
                           5:30 pm
                    Room 206, Science & Tech. I
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