An interstitialcy theory of structural relaxation and related viscous flow of glasses

A theory of isothermal structural relaxation and creep of glasses below the glass transition temperature is given. According to the interstitialcy theory, the supercooled liquid state does not exist below a Kauzmann pseudocritical temperature T-k, which lies above the temperature T-K, commonly called the Kauzmann temperature. Structural relaxation is simply a reduction with time of the interstitialcy concentration to the crystalline state for TT-k. The predicted viscosity eta is universal, given by eta=eta(0)+(eta) over dot(T)t, in agreement with experiment. eta is continuous in T, with (eta) over dot discontinuous at T-k but linear in 1/T above and below T-k. The dependence of eta on the shear modulus directly connects kinetic and thermodynamic properties of glasses and liquids.