Figure 1 : Free energy landscape with simple basins, metabasins and fractal basins.

From: Fractal free energy landscapes in structural glasses

Figure 1

Schematic depictions of (a) the liquid state at packing fractions ϕ that are smaller than the glass transition ϕg, and of free energy basins for different landscape scenarios: (b) simple stable basins, (c) metabasins of sub-basins (d) and metabasins of marginal basins. The simple landscape description is akin to boating on a system of lakes separated by high mountains. In the liquid, all of space can be explored. At lower water levels, each basin is a different glass. The free energy barriers hinder passing from one glass to another (the so-called α-relaxation); the basin width allows for vibrational relaxation. Both in c and d, the water level further determines what features of the landscape are experienced. Deep into the glass, the landscape roughness results in intra-state barriers that are associated with secondary relaxations. In d, at very low water levels (right)—deep into the fractal glass—lakes transform into a complex wetland with a hierarchy of small ponds. (e) The very bottom of each of these ponds corresponds to a given realization of the force network (red lines), but the identification of the force contacts remains undetermined before the fractal regime is reached (dashed line).