(360a) Exploring canyons in soft and glassy energy landscapes using metadynamics

The complex physics of glass forming systems is controlled by the structure of the low energy portions of their potential energy landscapes. The inability of glasses to equilibrate and find their lowest energy configurations is often attributed to their potential energy landscapes: rugged, barrier-filled surfaces in high-dimensional space that seem incredibly difficult to navigate. In this study, we report that a modified metadynamics algorithm (MIMSE) efficiently explores and samples low energy regions of such high-dimensional landscapes. In the energy landscape for a model foam, our algorithm finds and descends meandering ‘canyons’ in the landscape, which contain dense clusters of energy minima along their floors. Similar canyon structures in the energy landscapes of two model glass formers — hard sphere fluids and the Kob-Andersen glass - allow us to reach high densities and low energies, respectively. In the hard sphere system, fluid configurations are found to form continuous regions that cover the canyon floors up to densities well above the jamming transition. For the KobAndersen glass former, our technique samples low energy states with modest computational effort, with the lowest energies found approaching the predicted Kauzmann limit. In all three systems, our algorithm successfully uses these canyons as navigational aids to access low energy states deep within the potential energy landscape. The earlier-noted rugged surfaces line the canyon floors with smooth canyon walls; the algorithm successfully overcomes local ruggedness and explores low-energy regions of the landscape. Further, we observe that the underlying canyon have strikingly similar fractal character across these systems.