Large-scale molecular dynamics simulations of particulate ejection and Richtmyer-Meshkov instability development in shocked copper

Abstract
We present the results of recent large-scale, non-equilibrium molecular dynamics (NEMD) simulations of shock-induced surface instability development. We consider single crystal Cu described by an embedded atom method potential and driven by a shock wave along the [111] crystallographic direction, impinging upon a roughened Cu/vacuum or Cu/Ne interface. The NEMD simulation cell is a quasi-2D 2.23 μm×5.67 μm slab geometry, 1.5 nm thick in the (periodic) third dimension. The first third of the sample length (1.89 μm) is occupied by Cu (530 million atoms), and the remainder either empty vacuum or Ne gas (195 million atoms). The Cu/Ne (or Cu/vacuum) interface has an initial perturbation with average amplitude 30 nm and dominant wavelength of 0.74 μm. A shock wave is created by driving the front end of the Cu slab at a fixed particle velocity u_p = 2.0 to 3.5 km/s. Single-mode and multi-mode interfaces were considered using 212,992 CPUs of the LLNL BlueGene/L supercomputer for times on the order of 1 ns. The higher particle velocities studied here span shock Hugoniot and release states from solid to liquid, including the fluid-solid mixed phase.