Читать книгу Encyclopedia of Glass Science, Technology, History, and Culture - Группа авторов - Страница 299

Substituting Eqs. (12) and (14) in Eq. 16 and assuming that only one type of constraints (with n constraints per vertex) varies within the temperature range of interest, one obtains the following temperature scaling of viscosity for supercooled liquids:

(19)

For deeply supercooled liquids in the vicinity of the glass transition, n is approximately equal to 3 and Eq. (16) simplifies to

(20)

where B is a new constant. This Eq. (20) is the well‐known MauroYue‐Ellison‐Gupta‐Allan (MYEGA) expression [33] for the T‐dependence of the equilibrium viscosity, which has been remarkably successful in fitting the experimental data on the T‐dependence of viscosity for a large number of inorganic and organic liquids. It should be noted that, like the Vogel‐Tammann‐Fulcher (VFT) equation, the MYEGA has only three fitting parameters but, unlike VFT, it does not exhibit any divergence of viscosity at any finite temperature.