English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Plus monthly

Global: Zendy Tools annual

Global: Zendy Tools monthly

Global: Zendy Free Plan

Within the framework of the Adam-Gibbs (configurational entropy) theory of viscosity, it is shown that for a given composition, the ratio of parameters B e  (a temperature inde­pendent constant) to S c (T g ) (the configurational entropy at the glass transition) is propor­tional to the height of the average potential energy barrier to viscous flow (Δμ) and the size of the rearranging domains at the glass transition [z*(T g )]. The ratio B e /S c (T g ) is eval­uated for several silicate and aluminosilicate compositions of variable polymerization. It is found that the ratio B e /S c (T g ) shows simple compositional variations that correspond closely to those that may be expected qualitatively for the height of the potential energy barrier to viscous flow. Assuming that z(T g ) is a constant for all compositions, the avail­able data for B e /S c (T g ) are parameterized as a function of Δμ. The physical basis of this parameterization will therefore allow extension to more complex systems as additional data become available. The A e  term in the Adam-Gibbs equation (another temperature independent constant) shows only minor compositional variation (-2.6 ± 1). but the vari­ation that does exist is found to be a linear function of B e/ tetrahedron. The proposed parameterizations of B e /S c (T g ) and A e  are shown to be sufficient for estimating the glass transition temperature to within 15-20 K. Calculated glass transition temperatures may be combined with existing models for viscosities in the range 1O-1O 5  Pa·s. Interpolation pro­vides the whole viscosity curve and thus also an estimate of the departure from Arrhenian behavior. Although further work is necessary to verify) and extend the parameterizations to compositions of direct geological relevance, this work represents a step toward a fully generalizable predictive model of silicate melt viscosity based within a physical framework.

Energy barriers to viscous flow and the prediction of glass transition temperatures of molten silicates