Scratch defects modulated hot spots generation in laser irradiated RDX crystals: a 3D FDTD simulation

Insights into the interaction between laser and energetic materials offer possibility of manipulating and initiating explosives in a more precise, controllable way. Herein, we investigate the interaction between laser and cyclotrimethylene trinitramine (RDX) energetic crystals with scratch defects in the framework of three-dimensional finite difference time domain. Modulation effects on the hot spot formations have been explored for single scratch of parabolic/triangular geometries as well as two-scratch combination in parallel and intersecting configurations. The calculation results disclose that for single scratch, the width of scratch affects more on the light intensification than its depth. Meanwhile, scratch defects of triangular geometry exhibit stronger modulation effect than the parabolic ones. For two-scratch combinations, including both parallel and intersecting configurations, a coupling effect is found to promote generation of hot spots under laser irradiation. In particular, the triangular & triangular interaction presents largest enhancement on light intensification among diverse configurations. It also reveals that RDX crystals are more easily initiated when the intervals between two parallel scratches are appropriate ( λ –4 λ ), or the intersecting scratches are perpendicular with each other. This work offers a primary inspiration for better understanding the formation of hot spots under laser irradiation and provides practical guideline for the surface quality managements of explosive materials.