Dynamical characterization of active regions environments for ion dynamics in Lithium metasilicate glasses

• We simulate the dynamics of mobile lithium ions in lithium metasilicate glasses.
• We used the Molecular Dynamics formalism and the Isoconfigurational Ensemble Method.
• The ionic conducting channels and their environments were re-described in a new way.
• A strong correlation among the diffusing lithium ions was found.
• A cooperative movement among lithium ions (vacancy type) appears as highly probable.

Surprisingly, there is not a complete and general working theory for the ionic conduction on structurally disordered inorganic solids at present. In this context, lithium metasilicate glasses appear as paradigmatic and they have been extensively used for investigation in order to identify the main ingredients for a working theory of ionic conducting glasses. In particular among one of these main ingredients, the interaction among the mobile cations appears relevant, especially after recent results showing the existence of preferred pathways for ionic migration. We have performed Molecular Dynamics simulations on lithium metasilicate to better understand the ion-ion interactions. We introduce a very useful tool developed by Harrowell and co-workers (2004) [1] to study propensity to movement and the use of the Pearson's coefficient to characterize the correlation among the different kinds of ion. Our study allows us to support – from an alternative point of view – the idea of a landscape of energy for lithium ions with high propensity to movement (which eventually belongs to a high propensity cluster as defined in our previous work) and strongly dependent on the interaction among them. On the contrary, in the same window of time, these lithium ions do not strongly correlate with their nearest oxygen ions.