FIGURE 9.

Same data as in Fig. 8, but with all velocities and accelerations given in units of the mean velocity on a given surface. (A) Average and RMSD of acceleration's components, as function of speed/(mean speed). (B) Velocity distribution as function of speed/(mean speed). (C) Dimensionless velocity autocorrelation functions φ(t)/φ(0). They maybe distinguish two kinds of surfaces, the discriminator being the characteristic time of the exponentially decreasing tails. (D) Same as in panel C, but as function of reduced time, i.e., time divided by characteristic time of tail. Plotted this way, the tails all have slope 1. The data collapse is an additional result: the normalized correlation function of reduced time cannot distinguish surfaces.