An Effective Potential Approach to the Modeling of Concentrated Dusty Plasmas

尘埃等离子体由电子、离子和带电的微纳米颗粒组成，主要通过静电力相互作用。这个计算研究项目将重点关注空间电荷效应（由于附近存在其他电荷而导致的颗粒-离子力的扭曲）对单个颗粒和离子对颗粒施加的阻力的影响。这项研究的广泛意义将加强研究人员在等离子体半导体制造过程中的预测能力，其中尘埃形成是一个严重的污染问题，对天体物理过程的理解，如小行星和行星的形成，其中高电荷颗粒聚集和生长，以及热核聚变反应堆的建模，其中壁材烧蚀可能干扰聚变核心的维持。该项目的教育和推广活动将导致为高中和本科生设计的交互式软件工具，以培养对尘埃等离子体的直观感觉。作为提高女生在理工科领域参与度的“女生体验工程”拓展项目的一部分，项目组将开展为期一周的活动，提供编程、实验室演示和学术演讲的机会。模拟研究了高浓度的空间电荷（颗粒、离子和电子）和等离子体电场对浸没在尘埃等离子体中的单个颗粒的电荷和离子阻力的影响。这项工作的中心假设是，晶粒和离子/电子之间复杂的多体静电相互作用可以通过有效势来捕获，该有效势是通过平均单个晶粒周围所有可能的空间电荷构型而得到的。有效势将在朗之万框架中用于捕获静电相互作用（有效势）、中性阻力和布朗扩散的相互作用。通过分析由朗格万动力学模拟得出的颗粒-离子碰撞时间分布和颗粒-离子冲击力分布，建立颗粒电荷和离子阻力模型。开发的模型将根据已发表的实验和从PK-4谷物电荷和离子阻力测量活动中获得的数据进行测试。该项目有望解开与致密颗粒系统相关的相关颗粒运动的基本方面。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Dusty plasmas are comprised of electrons, ions and charged micro/nanometer-sized grains interacting with each other predominantly through electrostatic forces. This computational research project will focus on the impact of the space charge effect -- the distortion of grain-ion forces due to other charges being present in the vicinity -- on individual grains and on the drag force exerted by ions on grains. The broader implications of this research will fortify the prediction capabilities of researchers working on plasma-based semiconductor manufacturing processes where dust formation is a serious contamination issue, the understanding of astrophysical processes such as asteroid and planet formation where highly charged grains coalesce and grow, and modeling of thermonuclear fusion reactors where wall material ablation may interfere with the sustenance of the fusion core. The educational and outreach activities of this project will result in interactive software tools designed for high school and undergraduate students to develop an intuitive sense about dusty plasmas. As part of an outreach program called "Girls Experiencing Engineering" to increase the participation of female students in science and engineering, the project team will conduct a week-long event that will provide opportunities of programming, lab demos and scholarly presentations.A modeling investigation will be carried out to study the effect of a high concentration of space charge (grains, ions and electrons) and the plasma electric field on the charging of and the ion drag on an individual grain immersed in a dusty plasma. The central hypothesis to this effort is that the complex multi-body electrostatic interaction between grains and ions/electrons can be captured by an effective potential that is derived by averaging over all possible configurations of space charge around an individual grain. The effective potential will be used in a Langevin framework to capture the interplay of electrostatic interactions (effective potential), neutral drag and Brownian diffusion. Grain charging and ion drag models will be developed by analyzing the grain-ion collision time distribution and grain-ion impact force distribution inferred from Langevin Dynamics simulations. The developed models will be tested against published experiments and data obtained from PK-4 measurement campaigns of grain charging and ion drag. The project is expected to unravel basic aspects of correlated grain motion of relevance to dense granular systems.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.