Channel diffusion of sodium in a silicate glass

We use classical molecular dynamics simulations to study the dynamics of sodium atoms in amorphous Na$_2$O-4SiO$_2$. We find that the sodium trajectories form a well connected network of pockets and channels. Inside these channels the motion of the atoms is not cooperative but rather given by independent thermally activated hops of individual atoms between the pockets. By determining the probability that an atom returns to a given starting site, we show that such events are not important for the dynamics of this system.Comment: 10 pages of Latex, 5 figures, one figure added, text expande

Recent experiments on a small-angle/wide-angle X-ray scattering beam line at the ESRF

Recent results using a new combined small-angle/wide-angle X-ray scattering (SAXS/WAXS) beam line at the European Synchrotron Radiation Source (ESRF) will be presented. This beam line is specifically designed to be able to handle complicated sample environments required to perform time-resolved experiments mimicking processing conditions used in material science. Besides the attention that has been given to the interfacing of these sample environments to the beam line data acquisition system also the developments in detector technology will be discussed. The influence that a high count rate and low noise WAXS detector can have on the accuracy of experimental results in polymer crystallisation will be shown. It is shown that it is feasible to detect crystalline volume fractions as low as 10(-3)-10(-4) in polymeric systems