The reported relaxation time for several typical glass-forming liquids was analyzed by using a kinetic model for liquids which invoked a new kind of atomic cooperativity--thermodynamic cooperativity. The broadly studied 'cooperative length' was recognized as the kinetic cooperativity. Both cooperativities were conveniently quantified from the measured relaxation data. A single-exponential activation behavior was uncovered behind the super-Arrhenius relaxations for the liquids investigated. Hence the mesostructure of these liquids and the atomic mechanism of the glass transition became clearer.

On the basis of the kinetic model for liquids, which gave a quantitative description of liquid substructures, atomic relaxations in a model liquid were calculated. A crossover temperature Tcoop was recognized: relaxations were noncooperative at temperatures above Tcoop while cooperative below Tcoop. The cooperation in relaxation was responsible for the very slow dynamics near glass transition, departing significantly from the Arrhenius relation. This found supports in a large variety of glass forming liquids. The degree of cooperation in relaxation was straightforwardly determined by the number of atoms, N, in the liquid substructure and was responsible for the fragility of liquids: the larger the N was, the more fragile a liquid was.

The densities of liquid Bi, Sn, Pb and Sb have been precisely measured from the melting point up to about 1100 K using an improved Archimedean method. The densities at the melting point for liquid Bi, Sn, Pb and Sb are 10.042 × 103, 6.983 × 103, 10.635 × 103 and 6.454 × 103 kg m−3, respectively. Comparisons between our data and those from the literature have been made and they show the present results to be more reliable. Rather than a linear fit for the temperature dependence of the density, a slight deviation from linearity in the temperature dependence of the densities has been observed.

The temperature dependence of the local structure of liquid Sb has been studied by x-ray absorption spectroscopy. It is shown that about 10% of the atoms with coordination of 3 and weak Peierls distortion exist in liquid Sb just above its melting point. The Peierls distortion weakens gradually with increasing temperature and vanishes at about 750 degrees C. This structural variation in liquid Sb is different from the normal liquid-liquid phase transition. This work reveals the relationship between the variation in the local structure and the change in the physical properties, such as the electrical resisitvity of liquid Sb, with temperature. The complete agreement between the measured electrical resistivity values during heating and cooling processes suggests that the structural units with the features of a rhombohedron appear above the melting point of Sb during solidification.