Based upon simulations of a lithium metasilicate glass, a study was made of the potential of bond valence sum calculations for identifying sites and diffusion pathways for mobile Li ions in a glassy silicate network. It was found that the bond valence method was not well suited to the location of sites, but permitted the estimation of the number of sites. The spatial regions of the glass determined to be accessible to the Li ions according to the bond valence method could capture up to 90% of the diffusion path. These regions involved however a significant fraction that did not belong to the diffusion path. Because of this low specificity, care had to be taken to determine the diffusive motion of particles in amorphous systems based upon the bond valence method. The best identification of the diffusion path was achieved by using a modified valence mismatch in the bond valence analysis that took into account that a Li ion favored equal partial valences to the neighboring oxygen ions. Using this modified valence mismatch it was possible to replace the hard geometrical constraints formerly applied in the bond valence method.

Comparison of Ion Sites and Diffusion Paths in Glasses Obtained by Molecular Dynamics Simulations and Bond Valence Analysis. Müller, C., Zienicke, E., Adams, S., Habasaki, J., Maass, P.: Physical Review B, 2007, 75[1], 014203