Configurational entropy and the non-Newtonian rheology of homogeneous silicate liquids
Phys. Rev. B 49, 95 – Published 1 January, 1994
DOI: https://doi.org/10.1103/PhysRevB.49.95
Abstract
Recently, the non-Newtonian viscosity of silicate liquids at high stress levels has attracted a fair amount of attention. Different explanations for this interesting phenomenon have been proposed. The purpose of the present paper is to demonstrate that an extension of the configurational entropy theory for the occurrence of the glass transition by Adam and Gibbs [J. Chem. Phys. 43, 139 (1965)] suffices to explain the development of non-Newtonian viscosity in liquids under high stress before rupture occurs. Attention is drawn to the fact that under steady-state conditions the logarithmic values of reduced viscosities of silicate liquids under high stress show a linear dependence on the square of the applied stress. This relationship suggests that the elastic work done by the stress on the liquid is the cause of the generation of configurational entropy. Adding this contribution to the configurational entropy term in the Adam-Gibbs equation for the ensemble average of the configurational transition probability is all that is needed to explain the heretofore mentioned non-Newtonian viscosity in liquid silicates and a molecular-dynamics Lennard-Jones liquid.