Transport properties of sodium in a silicate glass: A numerical study

Abstract We study the dynamics of the Na atoms in amorphous Na2O-4SiO2 by means of molecular dynamics computer simulations. We find that at low temperatures the preferential pathways of these atoms form a well-connected network of pockets and channels that is quickly explored by each atom. We show that even for long times the volume occupied by these channels is relatively small and that they cannot be seen in individual snapshots of the Na atoms. By studying the distinct part of the van Hove correlation function we show that the lifetime for such a pocket shows an Arrhenius dependence on temperature. We also calculate the probability that an atom returns to a given site and show that such events are not very frequent.