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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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    Structural and Thermodynamic Properties of SiO2 Nano-clusters

			       Mark Kluge
		Laboratory for Computer Design of Materials
	   Institute for Computational Sciences and Informatics 
			George Mason University 

	Atomistic models of spherical SiO2 clusters were created for sizes 
ranging from 12 to 906 atoms. After annealing and cooling to T = 0, the
structural and thermodynamic properties were calculated. Clusters were found
to exhibit amorphous-like structures at all sizes with mean bondlengths 
slightly larger than in the bulk. The topological structures differed from
the bulk, with the presence 4, 6 and 8-member rings. The dynamical matrices
were diagonalized and Densities of statess, as well as thermodynamic 
properties (within the harmonic approximation) were calculated. The free 
energy was found to decrease as a function of cluster size at all 
temperatures, implying the relative thermodynamic stability of large 
clusters over smaller ones.   

                           Monday , March 25 1996
                                  5:00 pm
                          Room 206, Science & Tech. I
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