Dynamics of changes in stress autocorrelation functions of aluminum melt during ultrafast cooling
We present the results of the study of changes in liquid properties during ultrafast cooling. The molecular dynamics (MD) method is used, with aluminum melt as an example. Based on the changes in shear stress autocorrelation functions (SACF) with temperature in an ensemble of MD trajectories, we develop three approaches to the study of melt changes. In the first one, we investigate the asymptotic behavior of SACFs and a sharp increase in the melt viscosity, which is a conventional criterion. In the second approach, we present direct evidence of the transition of a metastable melt to a non-equilibrium state. In the third one, we show the appearance of transverse oscillations in a film of the melt. The most important observation is that all three phenomena occur in the same temperature range. On the basis of the current and the previous work, we conclude that there is a gap between the temperature of the splitting of the second peak of the pair correlation function and the temperature of the transition to a solid-like amorphous state. The splitting of the second peak occurs at a significantly higher temperature and this phenomenon is discussed.