Structure and dynamics of lithium silicate melts: molecular dynamics simulations

We present molecular dynamics simulations of lithium silicate melts with (Li2O)(x)(SiO2)(1-x) with Li2O concentrations x = 0.01, x = 0.1 and x = 0.5 in equilibrium conditions for temperatures down to 1500 K. The partial pair correlation functions are determined and compared with recent experimental data. The dynamics of the individual species is characterized via the mean square displacement. From the temperature dependence of the long-time diffusion constant we extract information about its activation energy. Interestingly, for x = 0.5 the extrapolation of the diffusion constant to temperatures below 700 K shows good agreement with experimental tracer diffusion data. In agreement with experiment, the length scale beyond which the dynamics becomes diffusive systematically varies with lithium concentration. Analysis of the van Hove self correlation function reveals how the occurrence of hopping processes as well as the presence of dynamic heterogeneities at low temperatures is correlated with the Li2O concentration.