Response of Jammed Ellipsoid Packings

We investigate the nature of the jamming transition for packings of spheroids by examining the elastic moduli as a function of the aspect ratio of the particles $\varepsilon$ and the compression. Irrespective of the particle aspect ratio, both shear modulus $G$ and bulk modulus $B$ show the same scaling as a function of compression as is found for packings of spheres. Moreover, for any value of $\varepsilon$, $G$ is proportional to the excess of the coordination number above that found at the jamming threshold; this recovers the result for frictionless spheres at $\varepsilon=1$. Our results imply a new diverging length scale associated with the loss of rigidity of these spheroid packings. The critical behavior of ellipsoid packings is an extension of that found for spheres.