Ergodicity breaking in strong and network-forming glassy systems

The temperature dependence of the nonergodicity factor of vitreous GeO₂, fq(T), 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 fq(T) 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 network-forming glassy systems.