solutions 2/2007 – Atomic movements in glass

Atomic movements in glass, schematically shown for a sodium silicate glass as an example (Si: red; sodium: green; bridging oxygen (BO): purple; non-bridging oxygen (nBO): brown): (a) Vibrations of a sodium ion about its site, observed at ~1012 -1013 Hz, independent of temperature (b) Diffusion of a sodium ion via hopping over an energy barrier, observed at ≥ room temperature and low frequencies, (c) Coupled hop of a single sodium ion, observed at ≤ room temperature and moderately high frequencies (kHz-MHz), and (d) ”Jellyfish” type wiggling motion of a group of atoms including both the network modifier and former atoms, observed at low temperatures (<200 K) and low/moderate frequencies as well as at room temperature and microwave frequencies.