Hypocoordinated solids in particulate media

Phys Rev E Stat Nonlin Soft Matter Phys. 2014 Jun;89(6):062203. doi: 10.1103/PhysRevE.89.062203. Epub 2014 Jun 12.

Abstract

We propose a "phase diagram" for particulate systems with purely repulsive contact forces, such as granular media and colloids. We characterize two classes of behavior as a function of the input kinetic energy per degree of freedom T_{0} and packing fraction deviation from jamming onset Δϕ=ϕ-ϕ_{J} using simulations of frictionless disks. Isocoordinated solids (ICS) exist above jamming; they possess an average contact number equal to the isostatic value z_{iso}. ICS display "strict" harmonic response, where the density of vibrational modes from the Fourier transform of the velocity autocorrelation function is a set of sharp peaks at eigenfrequencies ω_{k}{d} of the dynamical matrix. In contrast, hypocoordinated solids (HCS) occur above and below jamming and possess fluctuating networks of interparticle contacts but do not undergo cage-breaking particle rearrangements. The density of vibrational frequencies for the HCS is not a collection of sharp peaks at ω_{k}{d}, but it does possess a common form over a range of Δϕ and T_{0}.

Publication types

  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Colloids / chemistry
  • Computer Simulation
  • Fourier Analysis
  • Kinetics
  • Models, Chemical*
  • Particulate Matter / chemistry*
  • Temperature
  • Vibration

Substances

  • Colloids
  • Particulate Matter