Molecular dynamics study of the diffusion of sodium in amorphous silica

We study the dynamics of the sodium atoms in amorphous Na2O–4SiO2 using classical molecular-dynamics simulations. We find that the sodium trajectories form a well connected network of pockets and pathways intimately related to the location of the non-bridging oxygen atoms. Inside these channels the sodium atoms move by activated jumps. By determining the probability that an atom returns to a given starting site, we show that at the present concentration of sodium and over the investigated temperature range (1600–4000 K), such events are not important for the dynamics of this system. 2002 Elsevier Science B.V. All rights reserved.