On the form of the viscosity temperature dependence for glasses and their melts

A simple model is proposed, which gives an opportunity to evaluate a microscopic mechanism of viscous flow (the number of atoms, collectively participating in this process, and the elementary energy of bonds switching) from experimental data of the viscosity temperature dependence. The discussion is made for three typical glass forming substances: Se, SiO 2 and B 2O 3, and it is shown that not only the collective movement of atoms, but also the thermal generation of link-defects in a covalent network should be taken into account. The nature of the collectivity at viscous flow of glasses and their melts is discussed.