MOLECULAR DYNAMIC SIMULATION OF HETEROGENEITY AND CHEMICAL-STATES OF FLUORINE IN AMORPHOUS ALKALINE-EARTH SILICATE SYSTEMS

Chemical states of fluorine in fluorosilicate glasses in the system MF 2-MO-SiO2 (M = Ca, Sr and Ba; SiO2 content < 60 mol%) have been invest igated by molecular dynamic (MD) simulations with a perfect ionic two- body potential. Comparison of the results with those derived by X-ray photoelectron spectra of the actual glasses demonstrates that MD simul ations reproduce well the bonding states of fluorine in the systems as well as the formation of M-F clusters. The MD generated structure of imaginary glasses, or glasses not obtained by the conventional melt-qu ench technique, with 70 mol% SiO2 indicates that an acidic environment induces a greater amount of F-Si bonds. Their M-F pair correlation fu nctions plotted against normalized M-F distances suggest that relative ion positions in the clusters are very similar. (C) 1998 Elsevier Sci ence B.V.