Résumé:

We study the dynamics of the sodium atoms in amorphous Na2O-4SiO(2) 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.