Textured-amorphous diffraction from single-crystal Zr undergoing the α-to-ω phase transiition in molecular dynamics simulations

The nature of the prototypical pressure-induced α-to-ω phase transition in Zr has long been debated, due to the diversity of transformation pathways observed in different experimental and modelling contexts. Moreover, recent dynamic-compression experiments undertaken at the MEC instrument reveal that, in addition to crystalline Bragg peaks from its α and ω phases, single-crystal Zr exhibits a 'textured-amorphous' diffraction signature when shock-compressed along [0001]. We present the results of large-scale classical molecular dynamics (MD) simulations of Zr shock-compressed to its α-to-ω transition pressure, modelled under a machine-learned high-pressure potential. We partition the crystal into its constituent phase components using real-space coordination analyses, allowing us to monitor both the global phase-fraction evolution and the time-history of individual nanoclusters. We further examine the reciprocal-space structure of the sample's constituent parts, and find that the large fraction (~50%) of partially disordered material that pervades the sample brings about diffuse yet azimuthally localised diffraction, in agreement with experimental observations.