It is known that both loosening of glass structure and reduction of ionic diffusion coefficient occur in the mixed alkali system. We have performed molecular dynamics simulations of the mixed alkali system and have observed both characteristics in different time regions. A large decrease in the ionic diffusion coefficient is due to the interception of the jump where the jump path keeps its characteristics. The contribution of accelerated dynamics due to cooperative jumps decreases in such paths. On the other hand, in longer time regions, the motion of the framework has been found to accompany the small number of jump events of alkali metal ions to unlike ion sites. [S1063-651X(98)03210-3]. [References: 13]
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