Variable-cell method for stress-controlled jamming of athermal, frictionless grains

Kyle C. Smith, Massachusetts Institute of Technology
Ishan Srivastava, Purdue University, Birck Nanotechnology Center
Timothy Fisher, Purdue University, Birck Nanotechnology Center
Meheboob Alam, Jawaharlal Nehru Centre for Advanced Scientific Research

Abstract

A method is introduced to simulate jamming of polyhedral grains under controlled stress that incorporates global degrees of freedom through the metric tensor of a periodic cell containing grains. Jamming under hydrostatic (isotropic) stress and athermal conditions leads to a precise definition of the ideal jamming point at zero shear stress. The structures of tetrahedra jammed hydrostatically exhibit less translational order and lower jamming-point density than previously described maximally random jammed hard tetrahedra. Under the same conditions, cubes jam with negligible nematic order. Grains with octahedral symmetry having s > 0.5 (where s interpolates from octahedra [s = 0] to cubes [s = 1]) jam with an abundance of face-face contacts in the absence of nematic order. For sufficiently large face-face contact number, percolating clusters form that span the entire simulation box. The response of hydrostatically jammed tetrahedra and cubes to shear-stress perturbation is also demonstrated with the variable-cell method.

Discipline(s)

Nanoscience and Nanotechnology