One-dimensional moving window atomistic framework to model long-time shock wave propagation

Abstract

We develop a long-time, large-domain moving window atomistic framework using Molecular Dynamics (MD) to model shock wave propagation through a one-dimensional system. We implement ideas of control volume on a MD framework where a moving window follows a propagating shock. This circumvents issues such as boundary reflections and transient effects typically observed in conventional MD shock simulations. We model shock wave propagation through a one-dimensional chain of copper atoms using the Lennard-Jones, modified Morse, and Embedded Atom Model (EAM) interatomic potentials. The domain is divided into purely atomistic "window" atoms flanked by boundary, or continuum, atoms which incorporate either a Nose-Hoover or Langevin thermostat. The propagating shock wave is contained within the window region, while continuum shock conditions are imposed on the boundary atoms. The moving window effect is achieved by adding/removing atoms to/from the window and boundary regions. We perform verification studies to ensure proper implementation of the thermostats, potential functions, and moving window respectively. We then track the propagating shock and compare the actual shock velocity and average particle velocity to their corresponding input values. From these comparisons, we make corrections to the linear shock Hugoniot relation for the developed one-dimensional framework. Finally, we perform one-dimensional moving window simulations of a propagating stable-structured shock up to a few nanoseconds.