Compression Driven Jamming of Athermal Frictionless Spherocylinders in Two Dimensions

Abstract

We simulate numerically the compression driven jamming of athermal, frictionless, soft-core spherocylinders in two dimensions, for a range of particle aspect ratios $\alpha$. We find the critical packing fraction ${\varphi }_J(\alpha )$ for the jamming transition, and the average number of contacts per particle $z_J(\alpha )$ at jamming. We find that both are nonmonotonic, with a peak at $\alpha \approx 1$. We find that configurations at the compression driven jamming point are always hypostatic for all $\alpha$, with $z_J<z_{\mathrm{iso}}=2d_f=6$ the isostatic value. We show that, for moderately elongated spherocylinders, there is no orientational ordering upon athermal compression through jamming. We analyze in detail the eigenmodes of the dynamical matrix close to the jamming point for a few different values of the aspect ratio, from nearly circular to moderately elongated. We find that there are low frequency bands containing $N(z_{\mathrm{iso}}-z_J)/2$ modes, such that the frequency of these modes vanish as $\varphi \to {\varphi }_J$. We consider the extended vs localized nature of these low frequency modes, and the extent to which they involve translational or rotational motion, and find many low frequency sliding modes where particles can move with little rotation. We highlight the importance of treating side-to-side contacts, along flat sides of the spherocylinder, properly for the correct determination of $z_J$. We note the singular nature of taking the $\alpha \to 0$ limit. We discuss the similarities and differences with previous work on jammed ellipses and ellipsoids, to illustrate the effects that different particle shape have on configurations at jamming.

arXiv comment19 pages, 21 figures, revised with published version

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• Machine Learning Characterization of Structural Defects in Amorphous Packings of Dimers and Ellipses
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• Orientational Ordering in Athermally Sheared, Aspherical, Frictionless Particles
• Shear-Driven Flow of Athermal, Frictionless, Spherocylinder Suspensions in Two Dimensions: Stress, Jamming, and Contacts
• Jamming transition in non-spherical particle systems: pentagons vs. disks
• Stress propagation in locally loaded packings of disks and pentagons
• Shear-Driven Flow of Athermal, Frictionless, Spherocylinder Suspensions in Two Dimensions: Particle Rotations and Orientational Ordering
• Vibrational properties of two-dimensional dimer packings near the jamming transition
• Athermal shearing of frictionless cross-shaped particles of varying aspect ratio
• Shear thickening of suspensions of dimeric particles
• Packings of frictionless spherocylinders
• Depletion Forces in Athermally Sheared Mixtures of Frictionless Disks and Rods in Two Dimensions
• Distinct impacts of polar and nematic self-propulsion on active unjamming
• Testing mean-field theory for jamming of non-spherical particles: Contact number, gap distribution, and vibrational density of states
• Translational and rotational velocities in shear-driven jamming of ellipsoidal particles