Density fluctuations in granular piles traversing the glass transition: A grain-scale characterization via the internal energy

• Authors: Paula A Gago, Imperial College, London; Stefan Boettcher, Emory University
• Journal Title: SCIENCE ADVANCES
• Volume: Volume 8, Number 2
• Publisher: AMER ASSOC ADVANCEMENT SCIENCE | 2022-01-01, Pages eabl6304-eabl6304
• Type of Work: Article | Final Publisher PDF
• Publisher DOI: http://doi.org/10.1126/sciadv.abl6304
• Subjects: Physics, Astronomy and Astrophysics
• Keywords: Science & Technology; Multidisciplinary Sciences; Science & Technology - Other Topics; COMPACTION; LIQUIDS; MATTER

Abstract

The transition into a glassy state of the ensemble of static, mechanically stable configurations of a tapped granular pile is explored using extensive molecular dynamics simulations. We show that different horizontal subregions (“layers”) along the height of the pile traverse this transition in a similar manner but at distinct tap intensities. We supplement the conventional approach based purely on properties of the static configurations with investigations of the grain-scale dynamics by which the tap energy is transmitted throughout the pile. We find that the effective energy that particles dissipate is a function of each particle's location in the pile and, moreover, that its value plays a distinctive role in the transformation between configurations. This internal energy provides a “temperature-like” parameter that allows us to align the transition into the glassy state for all layers, as well as different annealing schedules, at a critical value.