Atomistic Modeling of the Generation of Metastable Nanoparticles and Surface Structures in Pulsed Laser Ablation in Liquids

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The generation of chemically clean and environmentally friendly nanoparticles through pulsed laser ablation in liquids has a number of advantages over conventional chemical synthesis methods and has evolved into a thriving research field attracting laboratory and industrial applications. This award supports fundamental research aimed at revealing, through advanced computer modeling and theoretical analysis, the mechanisms and kinetics of structural and phase transformations occurring in pulsed laser ablation in liquids. The emerging physical understanding of these phenomena will facilitate the development of new laser processing techniques capable of controlled generation of nanoparticles and surface structures with properties fine-tuned for biomedical, optical, photovoltaic, and sensing applications. This research will provide educational and training opportunities through the involvement of the participating students in high-performance parallel computing, and through broadening participation of U.S. university students in the Venice International School on Lasers in Materials Science.While, experimentally, the presence of the liquid environment has been demonstrated to strongly affect the nanoparticle size distributions and microstructure of laser-modified surfaces, the physical mechanisms of laser surface modification and ablation in liquids still remain elusive. This research will address the challenge of multi-scale computational modeling of laser ablation and processing in liquids by developing and applying an advanced computational model which combines a fully atomistic description of laser interactions with metal and semiconductor targets, a coarse-grained representation of liquid environment, and a continuum-level description of heat transfer from the irradiated surface. The simulations will target three interrelated focus areas: (1) study of the fundamental mechanisms of nanoparticle formation in pulsed laser ablation in liquids and evaluation of the dependences of various channels of nanoparticle formation on the irradiation conditions, properties of target material and liquid environment; (2) investigation of the ability of laser ablation in liquids to produce nanoparticles with unusual metastable structures, phase mixtures, and strong chemical supersaturation; and (3) analysis of the processes that control surface morphology and microstructure produced by laser processing in liquids. At the fundamental level, this study will provide unique insights into the material behavior far from equilibrium, under extreme conditions of ultrafast heating, cooling, and mechanical deformation.