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       SEMINAR OF THE LABORATORY FOR COMPUTER DESIGN OF MATERIALS
        Institute for Computational Sciences and Informatics
		CSI 929  (http://science.gmu.edu/physics/)
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    A Study of Dislocations in Silicon Using the Density Matrix Method

                             Ricardo W. Nunes
Institute for Computational Sciences and Informatics, George Mason University,
and  Complex Systems Theory Branch, Naval Research Laboratory, Washington D. C.

In this talk I present the results of our investigation of different 
aspects of the physics of dislocations in silicon. First, I briefly review 
the tight-binding density-matrix (TBDM) technique of Li, Nunes and 
Vanderbilt[1}, which is used in this work.The TBDM technique allows us 
to study large supercells (up to 864 atoms) while treating the electronic 
structure quantum-mechanically.    

I follow with a description of the results of our calculations. We focus 
mainly on the 90-degree partial dislocation along the [011] direction 
in a (11^1) slip plane. Its ground-state structure is determined, and 
we observe an asymmetric reconstruction with a breaking of the mirror 
symmetry along the dislocation line, as reported in other works. A variety 
of configurations that are likely to play a role in the formation and 
propagation of kinks along the dislocation are considered. ``Ground-state'' 
structures for these configurations are determined and the problem of 
the energy barriers involved in the motion of these kinks is addressed.

[1]X.P.Li, R.W.Nunes, and D.Vanderbilt, Phys. Rev. B 47, 10891 (1993)

	               Monday , September 30 1996
                                 5:00 pm
                        Room 206, Science & Tech. I
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