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

与传统的化学合成方法相比，脉冲激光在液体中制备化学清洁、环境友好的纳米粒子具有许多优点，已发展成为一个吸引实验室和工业应用的蓬勃发展的研究领域。该奖项支持旨在通过先进的计算机建模和理论分析揭示脉冲激光在液体中发生的结构和相变的机制和动力学的基础研究。对这些现象的新的物理理解将促进新的激光加工技术的发展，这些技术能够控制纳米颗粒和表面结构的产生，并具有可微调的特性，用于生物医学、光学、光伏和传感应用。这项研究将通过参与高性能并行计算的学生的参与以及通过扩大美国大学生对威尼斯国际激光在材料科学学院的参与来提供教育和培训机会。虽然从实验上已经证明，液体环境的存在强烈地影响了激光改性表面的纳米颗粒尺寸分布和微观结构，但激光表面改性和液体烧蚀的物理机制仍然不清楚。这项研究将通过开发和应用一种先进的计算模型来解决液体中激光烧蚀和加工的多尺度计算模型的挑战，该模型结合了激光与金属和半导体靶材相互作用的完全原子化描述、液体环境的粗粒度表示和来自受照射表面的热传递的连续水平描述。模拟将针对三个相互关联的焦点领域：(1)研究脉冲激光在液体中形成纳米颗粒的基本机制，并评估纳米颗粒形成的各种渠道与照射条件、目标材料的性质和液体环境的关系；(2)研究在液体中激光烧蚀产生具有异常亚稳态结构、相混合物和强化学过饱和度的纳米颗粒的能力；以及(3)分析控制激光在液体中产生的表面形貌和微观结构的过程。在基本层面上，这项研究将对材料在超高速加热、冷却和机械变形等极端条件下远离平衡的行为提供独特的见解。

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.