Lianwen Wang

Precise measurement of the densities of liquid Bi, Sn, Pb and Sb

The densities of liquid Bi, Sri, 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, Sri, Pb and Sb are 10.042 x 10(3), 6.983 x 10(3), 10.635 x 10(3) and 6.454 x 10(3) 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.

Vacancy-decomposition-induced lattice instability and its correlation with the kinetic stability limit of crystals

Vacancy decomposition kinetics in crystals at elevated temperatures is analysed. It is found that lattice instability is induced by a significantly enhanced vacancy decomposition at a critical temperature (T *). The critical temperature coincides with the kinetic instability limit (kinetic limit of superheating) of crystals in a variety of metals determined from the homogeneous nucleation catastrophe model.

Temperature effect of the local structure in liquid Sb studied with x-ray absorption spectroscopy

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.

A kinetic model for liquids: Relaxation in liquids, origin of the Vogel–Tammann–Fulcher equation, and the essence of fragility

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.

Correlating the stretched-exponential and super-Arrhenius behaviors in the structural relaxation of glass-forming liquids

Following the report of a single-exponential activation behavior behind the super-Arrhenius structural relaxation of glass-forming liquids in our preceding paper, we find that the non-exponentiality in the structural relaxation of glass-forming liquids is straightforwardly determined by the relaxation time, and could be calculated from the measured relaxation data. Comparisons between the calculated and measured non-exponentialities for typical glass-forming liquids, from fragile to intermediate, convincingly support the present analysis. Hence the origin of the non-exponentiality and its correlation with liquid fragility become clearer.

Comment on “Melting dynamics of superheated argon: Nucleation and growth” [J. Chem. Phys. 126, 034505 (2007)]

The way to obtain the critical liquid nucleus size N* in the above paper was argued to be not proper with a possibly undoubted and clear method proposed. Furthermore the importance of N* was discussed in view of recent progresses in the mechanism of melting.

Mechanochemical synthesis for studying the melting of metallic nanoparticles: a case study of copper

Mechanochemical synthesis is a promising method for studying the size-dependent melting of metals if the size of the resulting metallic nanoparticles can be tuned effectively. Here, with Cu as an example, we show that tuning of particle sizes can be accomplished by extending the milling time at a high milling speed and following annealing of the milled samples. With the so prepared samples, the melting point depression of Cu nanoparticles and its size dependence are successfully investigated.

Melting point depression method for determining the solid–liquid interfacial energy of metal elements: theoretical validation and updated compilation of data

Abstract Comparative analyses of the crystal nucleation method and the melting point depression (MPD) method for measuring the solid–liquid interface energy γsl are carried out. The MPD method is found more reliable and has several advantages from experiment through data analysis to theoretical generalisation. The MPD data in use, all reported before the 1970s, are updated with the derived γsl re-compiled. Finally, by invoking a melting model that we developed recently, an equation for calculating γsl is proposed on basis of the melting point depression method.