Undercooled phase behind the glass phase with superheated medium-range order above glass transition temperature

Abstract

Rapidly quenched glass formers are amorphous and transformed into glass phases by relaxing enthalpy during the first heating. Two liquids give rise, at first, to an intermediate Phase 3 below T3 < Tg respecting the entropy constraints and then, the enthalpy increases towards that of the glass phase up to Tg. The negative activation energy shows that Phase 3 is hidden behind the glassy phase acting as an intermediate invasive phase during the second cooling. Phase 3 carries a medium-range order above Tg which can be superheated above the melting temperature up to Tn+. The two-liquid state model predicts the thermodynamic properties as well as the relaxation times from liquids 1 to 2. The configuron model is successfully applied to 54 glasses explaining the transitions by percolation and an 'ordered' fraction equal to the critical threshold c = 0.15 ± 0.01 from Tg to Tn+.

Dewetting temperatures of prefrozen and grafted layers in solid ultrathin films viewed as melt-memory effects

“…The enthalpy coefficients are calculated with g3 = -0.14573 (Tg3 = 468.14 K) using (4)(5)(6)(7)(8)(9) to obtain lg = -0.15374 at Ta. They are given by (30)(31)(32):…”

Building and Breaking Bonds by Homogenous Nucleation in Glass-Forming Melts Leading to Transitions in Three Liquid States

“…The coefficient defined a new liquid phase called phase 3 undergoing a hidden phase transition below T g and a visible one at θ n+ , occurring for = θ n+ , as shown by Equation (7). This transition was accompanied by an exothermic latent heat equal to corresponding to about 15% of the melting heat [ 18 ]. Phase 3 was detected for the first time in supercooled water and associated with glacial phase formation [ 33 , 34 , 35 ] and recently appears as being associated with configuron formation [ 13 , 14 , 15 , 16 , 17 , 18 ].…”

“…This transition was accompanied by an exothermic latent heat equal to corresponding to about 15% of the melting heat [ 18 ]. Phase 3 was detected for the first time in supercooled water and associated with glacial phase formation [ 33 , 34 , 35 ] and recently appears as being associated with configuron formation [ 13 , 14 , 15 , 16 , 17 , 18 ]. The concept of configurons was initially proposed for materials with covalent bonds which can be either intact or broken [ 36 ]; then, it was extended to other systems including metallic systems based on ideas of Egami on bonds between nearest atoms in metals [ 16 , 37 ].…”

“…Both transition temperatures T g and T n+ are accompanied by enthalpy or entropy changes of phase 3 and are predicted in many cases: Annealing above and below T g , vapor deposition, formation of glacial and quasi-crystalline phases in perfect agreement with experiments. Any transformation of phase 3 changes the initial liquid enthalpy and rejuvenation at T g < T < T n+ does not lead to the enthalpy of the initial liquid [ 18 ].…”

“…A thermodynamic transition characterized by critical parameters occurs by breaking bonds (configurons) and when the percolation threshold of configurons is attained [ 13 , 14 , 15 , 16 , 17 ]. Building bonds by enthalpy relaxation below T g has for consequence the formation of a hidden undercooled phase called phase 3 with an enthalpy (ε ls (θ) − ε gs (θ)) ΔH m equal to that of configurons with a residual bond fraction which can be overheated up to T n+ > T m before being melted [ 18 ]. The homogeneous nucleation temperature at T n+ occurs in overheated liquids and is predicted for many molecular and metallic glass-forming melts.…”