Formation and stability of nanosized, undercooled propagating intermediate melt during β → δ phase transformation in HMX nanocrystal

The formation and stability of a nanosized propagating intermediate melt (IM) have been analyzed more than 150K below the melting temperature between the solid-solid (SS) phase boundary during beta -> delta phase transformation (PT) in a HMX nanocrystal. The influence of the solid-melt barrier K-12 and two important nanoscale material parameters (ratios of SS and solid-melt SM interface energies, k(E) and width, k(delta)) on the barrierless nucleation and appearance of non-equilibrium IM has been studied. Numerical results reveal that the solution of IM can either be continuous reversible or jump-like first-order discontinuous transformation with hysteresis. Additionally, various parametric studies on the structure, energy, width, and mobility of IM have been explored to understand the mystifying PT behaviors of HMX. Copyright (C) 2021 EPLA