ION DYNAMICS IN PURE AND MIXED-ALKALI GLASSES - SEPARATION OF THE SPATIAL AND TEMPORAL ASPECTS

Long time (similar to 1 ns region) molecular dynamics (MD) simulations of lithium metasilicate (Li2SiO3) and a mixed alkali silicate (LiKSiO 3) glass have been performed to confirm the mechanism of the ''mixed a lkali effect,'' which has been previously deduced from the shorter tim e behavior. In the Li2SiO3 system; long time behavior of lithium ion h as been characterized by a component showing the enhanced diffusion (L evy flight) due to cooperative jumps. The main diffusion and conductio n processes of silicate grasses are not the single jumps but the coope rative jumps. The component taking the accelerated dynamics is found t o be nearly absent in the mixed alkali system. Contributions of both t emporal and spatial aspects for the particle dynamics are separated. T he large change in the spatial parameters has been observed on mixing. Interception of the jump path due to other kinds of ion path suppress es the cooperative jump process.