arXiv subjects

R. C. Dennis

Publications and source records attributed to R. C. Dennis.

3 recordsLinked to original sources

arXiv2024

Methods for Creation and Linear Elastic Response Analysis of Packings of Semi-flexible Soft Polymer Chains

From understanding the sand on the beach to the foam on your beer, soft sphere simulations have been crucial to the study of the amorphous world around us. However, many of the materials we interact with on a daily basis aren't comprised of individual grains, but complex molecules and chains of polymers. By extending the soft sphere model to a model of linked spheres, we can learn more about the materials we interact with on a daily basis. In this methods paper, I show how one can find and study the physical properties of packings of flexible chains, rigid molecules, and everything in between. In addition to describing the energy landscape of these materials, these methods describe how to shear stabilize polymer packings, classify them in the jamming hierarchy, describe their elastic properties, and much more. This simple modification to soft sphere simulations has the potential to yield new discoveries surrounding glasses.

cond-mat.soft↗

arXiv2021

Dionysian Hard Sphere Packings are Mechanically Stable at Vanishingly Low Densities

High strength-to-weight ratio materials can be constructed by either maximizing strength or minimizing weight. Tensegrity structures and aerogels take very different paths to achieving high strength-to-weight ratios but both rely on internal tensile forces. In the absence of tensile forces, removing material eventually destabilizes a structure. Attempts to maximize the strength-to-weight ratio with purely repulsive spheres have proceeded by removing spheres from already stable crystalline structures. This results in a modestly low density and a strength-to-weight ratio much worse than can be achieved with tensile materials. Here, we demonstrate the existence of a packing of hard spheres that has asymptotically zero density and yet maintains finite strength, thus achieving an unbounded strength-to-weight ratio. This construction, which we term Dionysian, is the diametric opposite to the Apollonian sphere packing which completely and stably fills space. We create tools to evaluate the stability and strength of compressive sphere packings. Using these we find that our structures have asymptotically finite bulk and shear moduli and are linearly resistant to every applied deformation, both internal and external. By demonstrating that there is no lower bound on the density of stable structures, this work allows for the construction of arbitrarily lightweight high-strength materials.

cond-mat.soft↗

arXiv2020

Jamming Energy Landscape is Hierarchical and Ultrametric

The free energy landscape of mean field marginal glasses is ultrametric. We demonstrate that this feature remains in finite three dimensional systems by finding sets of minima which are nearby in configuration space. By calculating the distance between these nearby minima, we produce a small region of the distance metric. This metric exhibits a clear hierarchical structure and shows the signature of an ultrametric space. That such a hierarchy exists for the jamming energy landscape provides direct evidence for the existence of a marginal phase along the zero temperature jamming line.

cond-mat.soft↗