关键词: laser-material interaction, molecular dynamics (MD) simulation, ablation crater morphology, magnesium

Abstract: The micro-ablation processes and morphological evolution of ablative craters on single-crystal magnesium under subpicosecond laser irradiation are investigated using molecular dynamics (MD) simulations and experiments. The simulation results exhibit that the main failure mode of single-crystal Mg film irradiated by a low fluence and long pulse width laser is the ejection of surface atoms, which has laser-induced high stress. However, under high fluence and short pulse width laser irradiation, the main damage mechanism is nucleation fracture caused by stress wave reflection and superposition at the bottom of the film. In addition, Mg$[0\,0\,0\,1]$ has higher pressure sensitivity and is more prone to ablation than Mg$[1\,0\,\overline 1 \,0]$. The evolution equation of crater depth is established using multi-pulse laser ablation simulation and verified by experiments. The results show that, under multiple pulsed laser irradiation, not only does the crater depth increase linearly with the pulse number, but also the quadratic term and constant term of the fitted crater profile curve increase linearly.

Key words: laser-material interaction, molecular dynamics (MD) simulation, ablation crater morphology, magnesium