Cover Picture: (Prop., Explos., Pyrotech. 8/2022)

The cover picture shows : a head‐to‐head comparison between molecular dynamics (MD) and continuum predictions of the shock‐induced collapse of an elongated pore in inert ß‐HMX. The continuum material model used is strongly informed by fundamental properties obtained from MD. The simulations were performed for nearly identical sample geometries and boundary conditions, and the results shown are for identical times. The long axis of the pore was parallel to the initial shock direction, which is vertically upward in the images. The top row shows instantaneous HMX molecular center‐of‐mass positions and a Schlieren rendering of the continuum mass density, and the bottom row corresponding spatial distributions of local von Mises stress in the samples. The continuum results are in qualitatively good agreement with the 'ground truth' MD predictions, suggesting that the continuum model captures the salient aspects of the nanoscale physics. Background HMX microstructure image courtesy of Chris Molek, Eric Welle, and Ryan Wixom.