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. The influence of medium range order is presented and the unusual behavior of T-g in binary B2S3 and P2S5 systems explained by the presence of modifier-rich clusters (denoted by B-B doublets).