Ergodicity breaking in strong and network-forming glassy systems

The temperature dependence of the nonergodicity factor of vitreous GeO2, fqT, as deduced from elastic and quasielastic neutron scattering experiments, is analyzed. The data are collected in a wide range of temperatures from the glassy phase, up to the glass-transition temperature, and well into the undercooled liquid state. Notwithstanding the investigated system is classified as prototype of strong glass, it is found that the temperature and the q behavior of fqT follow some of the predictions of mode coupling theory. The experimental data support the hypothesis of the existence of an ergodic to nonergodic transition also in networkforming glassy systems.