The slope equations: a universal relationship between local structure and glass transition temperature

In this article, we present a universal relationship between the glass transition temperature $T_g$ and the local glass structure. The derivation of the simplest expression of this relationship and some comparisons with experimental $T_g$ values have already been reported in a recent letter. We give here the analytical expression of the parameter $\beta$ of the Gibbs-Di Marzio equation and also new experimental probes for the validity of the relationship, especially in low modified binary glasses.Comment: 31 pages, LaTeX, 16 Postscript figures, [email protected]

Solvable models of Glass Transition

Simple statistical agglomeration models can provide a universal link between the local structure and the glass transition temperature in network glasses. We first stress the physical features of the models and the hypothesis made, and then show how to define the glass transition temperature. The models are applied to various types of binary, ternary and multicomponent chalcogenide glass networks and the predictions compared to experimental data.Comment: 11 pages, Revtex, 5 EPS figures, Proceedins of the Cargese CNRS school "Physics of glasses: structure and dynamics", Cargese May 199

On the glass transition temperature in covalent glasses

We give a simple demonstration of the formula relating the glass transition temperature, $T_g$, to the molar concentration $x$ of a modifier in two types of glasses: binary glasses, whose composition can be denoted by $X_nY_m+xM_pY_q$, with ^$X$ an element of III-rd or IV-th group (e.g. B, or Si, Ge), while $M_pY_q$ is an alkali oxide or chalcogenide; next, the network glasses of the type $A_xB_{1-x}$, e.g. $Ge_xSe_{1-x}$, $Si_xTe_{1-x}$, etc. After comparison, this formula gives an exact expression of the parameter $\beta$ of the modified Gibbs-Di Marzio equation.Comment: 15 pages, LateX; ([email protected]), ([email protected]

Melt homogenization and self-organization of chalcogenides glasses: evidence of sharp rigidity, stress and nanoscale phase separation transitions in the GexSe100-x binary

A Raman profiling method is used to monitor growth of GexSe100-x melts and reveals a two step process of homogenization. Resulting homogeneous glasses show the non-reversing enthalpy at Tg, {\Delta}Hnr(x), to show a square-well like variation with x, with a rigidity transition near xc(1) = 19.5(5)% and stress transition near xc(2) = 26.0(5)%) representing the boundaries of the rigid but stress-free Intermediate Phase (IP). The square-well like variation of {\Delta}Hnr(x) develops sloping walls, a triangular shape and eventually disappears in glasses having an increasing heterogeneity. The {\Delta}Hnr term ages over weeks outside the IP but not inside the IP. An optical analogue of the reversibility window is observed with Raman spectra of as-quenched melts and Tg cycled glasses being the same for glass compositions in the IP but different for compositions outside the IP. Variations of Molar volumes, display three regimes of behavior with a global minimum in the IP and a pronounced increase outside that phase. The intrinsic physical behavior of dry and homogeneous chalcogenides glasses can vary sharply with composition near elastic and chemical phase transitions, showing that the physics of network glasses requires homogeneous samples, and may be far more interesting than hitherto recognized