### Abstract

Dense random packings of hard particles are useful models of granular media and are closely related to the structure of nonequilibrium low-temperature amorphous phases of matter. Most work has been done for random jammed packings of spheres and it is only recently that corresponding packings of nonspherical particles (e.g., ellipsoids) have received attention. Here we report a study of the maximally random jammed (MRJ) packings of binary superdisks and monodispersed superballs whose shapes are defined by ^{|} x1 ^{|} 2p ^{+ +} ^{|} xd ^{|} 2p ≤1 with d=2 and 3, respectively, where p is the deformation parameter with values in the interval (0,∞). As p increases from zero, one can get a family of both concave (0<p<0.5) and convex (p≤0.5) particles with square symmetry (d=2), or octahedral and cubic symmetry (d=3). In particular, for p=1 the particle is a perfect sphere (circular disk) and for p→∞ the particle is a perfect cube (square). We find that the MRJ densities of such packings increase dramatically and nonanalytically as one moves away from the circular-disk and sphere point (p=1). Moreover, the disordered packings are hypostatic, i.e., the average number of contacting neighbors is less than twice the total number of degrees of freedom per particle, and yet the packings are mechanically stable. As a result, the local arrangements of particles are necessarily nontrivially correlated to achieve jamming. We term such correlated structures "nongeneric." The degree of "nongenericity" of the packings is quantitatively characterized by determining the fraction of local coordination structures in which the central particles have fewer contacting neighbors than average. We also show that such seemingly "special" packing configurations are counterintuitively not rare. As the anisotropy of the particles increases, the fraction of rattlers decreases while the minimal orientational order as measured by the tetratic and cubatic order parameters increases. These characteristics result from the unique manner in which superballs break their rotational symmetry, which also makes the superdisk and superball packings distinctly different from other known nonspherical hard-particle packings.

Original language | English (US) |
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Article number | 041304 |

Journal | Physical Review E - Statistical, Nonlinear, and Soft Matter Physics |

Volume | 81 |

Issue number | 4 |

DOIs | |

State | Published - Apr 15 2010 |

Externally published | Yes |

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### ASJC Scopus subject areas

- Condensed Matter Physics
- Statistical and Nonlinear Physics
- Statistics and Probability

### Cite this

*Physical Review E - Statistical, Nonlinear, and Soft Matter Physics*,

*81*(4), [041304]. https://doi.org/10.1103/PhysRevE.81.041304

**Distinctive features arising in maximally random jammed packings of superballs.** / Jiao, Yang; Stillinger, F. H.; Torquato, S.

Research output: Contribution to journal › Article

*Physical Review E - Statistical, Nonlinear, and Soft Matter Physics*, vol. 81, no. 4, 041304. https://doi.org/10.1103/PhysRevE.81.041304

}

TY - JOUR

T1 - Distinctive features arising in maximally random jammed packings of superballs

AU - Jiao, Yang

AU - Stillinger, F. H.

AU - Torquato, S.

PY - 2010/4/15

Y1 - 2010/4/15

N2 - Dense random packings of hard particles are useful models of granular media and are closely related to the structure of nonequilibrium low-temperature amorphous phases of matter. Most work has been done for random jammed packings of spheres and it is only recently that corresponding packings of nonspherical particles (e.g., ellipsoids) have received attention. Here we report a study of the maximally random jammed (MRJ) packings of binary superdisks and monodispersed superballs whose shapes are defined by | x1 | 2p + + | xd | 2p ≤1 with d=2 and 3, respectively, where p is the deformation parameter with values in the interval (0,∞). As p increases from zero, one can get a family of both concave (0

AB - Dense random packings of hard particles are useful models of granular media and are closely related to the structure of nonequilibrium low-temperature amorphous phases of matter. Most work has been done for random jammed packings of spheres and it is only recently that corresponding packings of nonspherical particles (e.g., ellipsoids) have received attention. Here we report a study of the maximally random jammed (MRJ) packings of binary superdisks and monodispersed superballs whose shapes are defined by | x1 | 2p + + | xd | 2p ≤1 with d=2 and 3, respectively, where p is the deformation parameter with values in the interval (0,∞). As p increases from zero, one can get a family of both concave (0

UR - http://www.scopus.com/inward/record.url?scp=77951141726&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=77951141726&partnerID=8YFLogxK

U2 - 10.1103/PhysRevE.81.041304

DO - 10.1103/PhysRevE.81.041304

M3 - Article

AN - SCOPUS:77951141726

VL - 81

JO - Physical Review E - Statistical, Nonlinear, and Soft Matter Physics

JF - Physical Review E - Statistical, Nonlinear, and Soft Matter Physics

SN - 1539-3755

IS - 4

M1 - 041304

ER -