Mixed Alkali Effect in Alkali Metasilicate Glasses

概要

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Molecular dynamics (MD) simulation was performed for LiKSio_3 glass to clarify the mechanism of the "mixed alkali effect". In LiKSiO_3 glass at 800 K (near T_g), jump paths of Li and K ion are visualized. Each kind of alkali metal ions clearly shows an independent path. Each jump path has a low dimensional structure in (short) localized regions, while each path forms percolation clusters of various sizes. The larger probability of the back-correlation in the mixture than that in the pure salts contributes to the mixed alkali effect. Cooperative jumps of like ions are found to play an important role in the high conductivity of the pure Li containing glass and decreased contribution of the cooperative jumps to bulk diffusion coefficients explains the anomalous increase in the Haven ratio in the mixed alkali system. Namely, the interception of the jump paths in the mixture affects a collective motion more than a single ion motion.
理論物理学刊行会の論文
1997-06-27