Ultradense Sphere Packings Derived From Disordered Stealthy Hyperuniform Ground States

Abstract

Disordered stealthy hyperuniform (SHU) packings are an emerging class of exotic amorphous two-phase materials endowed with novel physical properties. Such packings of identical spheres have been created from SHU point patterns via a modified collective-coordinate optimization scheme that includes a soft-core repulsion, besides the standard `stealthy' pair potential. Using the distributions of minimum pair distances and nearest-neighbor distances, we find that when the stealthiness parameter $\chi$ is lower than 0.5, the maximal values of $\phi$, denoted by $\phi_{\max}$, decrease to zero on average as the particle number $N$ increases if there are no soft-core repulsions. By contrast, the inclusion of soft-core repulsions results in very large $\phi_{\max}$ independent of $N$, reaching up to $\phi_{\max}=1.0, 0.86, 0.63$ in the zero-$\chi$ limit and decreasing to $\phi_{\max}=1.0, 0.67, 0.47$ at $\chi=0.45$ for $d=1,2,3$, respectively. We obtain explicit formulas for $\phi_{\max}$ as functions of $\chi$ and $N$ for a given $d$. For $d=2,3$, our soft-core SHU packings for small $\chi$ become configurationally very close to the jammed hard-particle packings created by fast compression algorithms, as measured by the pair statistics. As $\chi$ increases beyond $0.20$, the packings form fewer contacts and linear polymer-like chains. The resulting structure factors $S(k)$ and pair correlation functions $g_2(r)$ reveal that soft-core repulsions significantly alter the short- and intermediate-range correlations in the SHU ground states. We also compute the spectral density $\tilde{\chi}_{_V}(k)$, which can be used to estimate various physical properties (e.g., electromagnetic properties, fluid permeability, and mean survival time) of SHU two-phase dispersions. Our results offer a new route for discovering novel disordered hyperuniform two-phase materials with unprecedentedly high density.