Based upon molecular dynamics simulations of a Li metasilicate glass, a study was made of the potential of bond valence-sum calculations for the identifying sites and diffusion pathways of mobile Li ions in a glassy silicate network. It was found that the bond valence method was not well-suited to site-location, but permitted estimations to be made of the number of sites. Spatial regions of the glass, which were designated as being accessible by Li ions for the bond valence method, could capture up to 90% of the diffusion. However, these regions involved a significant fraction that did not belong to the diffusion path. Because of this low specificity, care had to be taken when determining 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 account of the fact that a Li ion favored equal partial valences to the neighboring O ions. By using this modified valence mismatch, it was possible to replace the hard geometrical constraints, formerly applied in the bond valence method. Further investigation was required in order to understand better the relationship between the complex structure of the host network and the ion diffusion paths.

Comparison of Ion Sites and Diffusion Paths in Glasses Obtained by Molecular Dynamics Simulations and Bond Valence Analysis. C.Müller, E.Zienicke, S.Adams, J.Habasaki, P.Maass: Physical Review B, 2007, 75[1], 014203 (11pp)