Ordering and structural changes at the glassliquid transition
Abstract
Ordering types of amorphous solids and structural changes which occur at glassliquid transition are discussed focusing on configuron percolation theory (CPT) of glass transition. The glass transition temperature can be calculated using bond thermodynamic parameters e.g. enthalpy H_{d} and entropy of formation S_{d}. Explicit equations have been derived to assess H_{d} and S_{d} from available data on viscosity of amorphous materials using the CPT viscosity equation. A universal equation for the variable activation energy of viscous flow Q(T) has been found. The glassliquid transition is accompanied by formation of a percolation macroscopic cluster made up of broken bonds  configurons  which are dynamic in nature. The characteristic linear size of dynamic clusters formed is given by correlation length which universally depends on formation Gibbs free energy of configurons G_{d} = H_{d}  TS_{d} and becomes macroscopic at glass transition. Fractaltype medium range order (MRO) is revealed at correlation length sizes and homogeneous and isotropic disordered state (DS) characteristic for macroscopic sizes larger than the correlation length. The reduction of topological signature (Hausdorff dimensionality) of disordered bonding lattice from 3 for glass to fractal D_{f} = 2.4  2.8 for melt is the main signature change to explain the drastic changes of material behaviour at glass transition.
 Publication:

Journal of Non Crystalline Solids
 Pub Date:
 December 2013
 DOI:
 10.1016/j.jnoncrysol.2013.10.016
 Bibcode:
 2013JNCS..382...79O
 Keywords:

 Glasses;
 Melts;
 Phase transition;
 Fractal;
 Percolation