Polycluster liquid

Studying the kinetics of the liquid-solid transformation shows that the polycluster-structure formation competes with crystallization and, under certain conditions, it becomes dominant and leads the liquid to transfer to the glassy state (Sect. 6.2). 

In the physics of glasses, the clarification of the nature and the description of the glass-liquid transition are of particular interest. In polyclusters, the restoration of ergodicity begins with the melting of boundaries. The thermodynamics of this transition is considered in Sect. 6.8. 

The main purpose of this section is to give an account of general peculiarities of the microscopic scenarios of the supercooled liquid solidification and to show that formation of the polycluster glasses is a commonplace case. A more detailed consideration of the supercooled liquid structure, its thermodynamics and solidification kinetics is given in Sect. 6.10. 

The low-energy excitations described above contribute essentially to the reversible relaxation processes [6.32], to the internal friction [6.33], and to the specific heat. The expressions for the excitation contributions ii)—iii) to the specific heat are given in [6.29, 30], where it is also shown that cooperative rearrangements iii) contribute greatly to the melting of cluster boundaries which is treated as the glass-liquid transition in polyclusters (Sect. 6.8). 

The temperature T is the kinetic temperature of vitrification. The liquid cooled down to temperatures below T transforms into a polycluster amorphous solid even at stationary temperature. Since the crystallization and clusterization are the competing processes, it is of importance to know how the volume fraction and the cluster size distribution depend on the cooling rate. The answer to this question has been obtained by integrating the Avrami-Kolmogorov equations [6.81] generalized to the case of simultaneous formation of two new phases. The consideration of these results is beyond the scope of the present communication and will be published elsewhere [6.82]. 

Our main aim was to clarify the role of clusters in the process of liquid solidification and to show that formation of the polycluster glass structure is a typical result of this process. On the basis of the developed approach, such important problems as entropy crisis and relaxation phenomena in supercooled liquids can be considered in detail, but this is far from the topic of this paper and will be considered elsewhere. 

---