Sommaire:

The long slow decaying potential part of the stress autocorrelation function has been called the “molasses tail” to distinguish it from the hydrodynamic origin of the long time tail in the velocity autocorrelation functions and to emphasize its relation to highly viscous glassy state. We are investigating the molasses tail in dense hard core fluids by using extensive Event-Driven MD simulation through the orientational autocorrelation functions[1, 2]. Near the fluid-solid phase transition, there exist three regimes in the relaxation of the pair orientational autocorrelation function, namely the kinetic, molasses(stretched exponential), and diffusional power decay. The most striking observation through the bond orientatinal order parameter is the dramatic increase of the transient nuclei cluster size near the freezing density[2]. We are now improving the alternative general methods based on the autocorrelation functions of higher order parameters even for quadruplet contributions (i.e. 8 point-correlation) to establish the transient nuclei, which are composed of a few hundred hard particles in dense liquid system [3].

[1] M. Isobe and B. J. Alder, Mol. Phys. 107, 609 (2009).
[2] M. Isobe and B. J. Alder, Prog. Theor. Phys. Suppl. 184, 437 (2010).
[3] M. Isobe and B. J. Alder, in preparation.

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