Structural transitions in granular packs: statistical mechanics and statistical geometry investigations
Department of Applied Mathematics, The Australian National University, 0200 Canberra, ACT, Australia
Corresponding author: a email@example.com
Revised: 13 March 2008
Published online: 18 June 2008
We investigate equal spheres packings generated from several experiments and from a large number of different numerical simulations. The structural organization of these disordered packings is studied in terms of the network of common neighbours. This geometrical analysis reveals sharp changes in the network's clustering occurring at the packing fractions (fraction of volume occupied by the spheres respect to the total volume, ρ) corresponding to the so called Random Loose Packing limit (RLP, ) and Random Close Packing limit (RCP, ). At these packing fractions we also observe abrupt changes in the fluctuations of the portion of free volume around each sphere. We analyze such fluctuations by means of a statistical mechanics approach and we show that these anomalies are associated to sharp variations in a generalized thermodynamical variable which is the analogous for these a-thermal systems to the specific heat in thermal systems.
PACS: 45.70.-n – Granular Systems / 45.70.Cc – Static sandpiles; Granular Compaction / 81.05.Rm – Porous materials; granular materials
© EDP Sciences, Società Italiana di Fisica, Springer-Verlag, 2008