Supercooled liquids crossover temperature

Inherent structure analysis of diffusion via molecular dynamics of a deeply supercooled binary Lennard-Jones fluid have provided renewed impetus to the decisive role played by thermodynamic factors [52,53]. The location of the mode crossover temperature and the onset of super-Arrhenius behavior were related to the static structure of the liquid via the potential energy hypersurface [52,53],... 

The universality of the relaxation time near the crossover temperature also originates in the dynamic nature of supercooled liquids. The idea here is that supercooled liquids have collective excitations. These elementary excitations have characteristics of phonons [119-122]. Furthermore, there is a unique temperature at which the lifetime for the elementary excitation becomes comparable to the lifetime of hopping dynamics on the potential energy surface [119]. Analysis indicates that the value of crossover relaxation time at this characteristic temperature is < ) x 10-7 5 s, where < ) varies between 1 and [ 119]. 

We show that transient metastable rotator phases occur on crystallization of octadecane (CH3 (CH2)j6 CH3) and other even chain-length alkanes into their tiiclinic phase from the supercooled melt. This was directly observed using time resolved x-ray scattering. The crystallization temperature (i.e. the limit of supercooling) is determined by the thermodynamic stabili of the transient phase with respect to the liquid. We explain the crystallization kinetics of the homologous series of n-alkanes in terms of a crossover from stability to long-lived metastability to transient metastability. Such metastable and transient phases are likely to have analogues in polymeric systems. 

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