ABSTRACT
This chapter discusses the mechanism of ionic motions in silicate systems derived from molecular dynamics (MD) simulations. The time development of mean-squared displacement of ions shows several characteristic time regions. Details of ionic motions are examined from caged ion dynamics to diffusive dynamics step by step. The dynamic heterogeneity found in ionically conducting glasses is discussed, although the phenomena are common with non-ionic glass-forming materials. To understand the characteristics of dynamic heterogeneity, motions of ions including individual ones have been examined in several MD works. The data obtained by molecular dynamics simulations are adopted to examine further details of the dynamic heterogeneity. Since heterogeneity in structures and/or dynamics is widely found in nanostructured materials such as catalysts, colloidal systems, it will be interesting to examine the relationship with the functions of systems and heterogeneity of systems. The mean-squared displacements of ionic motion in lithium silicate glasses show several distinct time regions from caged ion dynamics to final diffusive motions.
