Rapid Compression of Prototype Sand-like Systems using Atomistic Molecular Dynamic Simulations

Porous materials offer many challenges in modeling because stress-chains, phase transitions and/or chemical reactions may be occurring. The granular Hugoniot response like for SiO$_{\mathrm{2}}$ compacts and at low initial macro-densities will yield a stiffer response compared to a fully dense sample [Trunin 2001]. K. Cochrane \textit{et al}.$^{\mathrm{\thinspace }}$[2017] introduced the hypothesis of surface energy for the initial Hugoniot energy E$_{\mathrm{o}}$ using DFT constrained by a Hugoniot-stat. We test this hypothesis but allowing the system to dynamically respond within the atomistic microcanonical (NVE) ensemble. We use atomistic MD simulations using Tersoff potential for nanometer-sized granules to investigate the underlying mechanism for the SiO$_{\mathrm{2}}$ Hugoniot. We first establish a Hugoniot baseline for a single crystal SiO$_{\mathrm{2}}$ system, then we use nearly spherical granules of SiO$_{\mathrm{2}}$ in close-packed configurations. Additionally, we have applied the similar methodology to SiO$_{\mathrm{2}}$ systems with voids for comparison.