Bridging Time Scales with a Unit Process Approach for Modeling Ion Interactions with Materials

时间尺度与离子与材料相互作用建模的单元过程方法在本项目中，将开发一种新的方法来模拟离子与材料相互作用应用中的多时间尺度问题。我们将此称为单元过程方法，其中使用原子建模方法来提取单个事件在短时间尺度上的平均影响，然后将数据合并到长时间尺度模型中，以实现较大和较慢的系统演化。这种方法将通过两个具体的任务对离子与材料相互作用中的一类问题进行演示。首先，离子轰击的基本单元过程模型将更加量化；初步工作中展示的两个例子是用于轰击非晶态表面的陨石坑函数方法和用于轰击晶体表面的缺陷统计方法。第二，这些改进的单元过程模型将被结合到两种类型的长时间尺度系统形态研究中，即(I)基于凹坑函数的离子轰击非晶态表面经过离子粗化和扩散平滑的表面演化研究，以及(Ii)离子轰击晶体表面形态的浓度演化方程研究，其中离子诱导缺陷浓度的统计群演化主导表面结构。新方法将引入一个在力学建模中连接多个时间尺度的强大框架，使精确的力学模型成为可能，跨越时间尺度从飞秒到数小时。它还将导致在理解离子与半导体的相互作用方面取得重大进展，这将影响离子注入、表面改性和研磨领域，以及航空航天和能源应用的辐射损害。该项目还将在UIUC和其他地方产生重要的教育影响。在该计划的第一年，PI将帮助在UIUC建立工程科学学会(SES)的学生分会，并将利用在UIUC举行的2008年SES会议来帮助发展该分会。学生章节的成员将来自机械工程和工程力学的本科生和研究生。

Bridging Time Scales with a Unit-Process Approach for Modeling Ion Interactions with MaterialsIn this program a new approach will be developed for modeling multi-timescale problems with applications in ion interactions with materials. We refer to this as a unit-process approach, whereby atomistic modeling methods are used to extract the average effects of single events at the short time scale, and then the data are incorporated in long time scale models for the larger and slower system evolution. The approach will be demonstrated for a class of problems in ion interactions with materials, via two specific tasks. First, basic unit-process models for ion-bombardment will be made more quantitative; the two examples demonstrated in preliminary work are the crater function approach for bombardment of amorphous surfaces, and the defect statistics approach for bombardment of crystalline surfaces. Second, these improved unit-process models will be incorporated into two types of long time scale system morphology studies, namely (i) crater function based surface evolution studies of ion bombarded amorphous surfaces undergoing ion roughening and diffusional smoothing, and (ii) concentration evolution equation studies of ion bombarded crystalline surface morphology, where statistical populations of ion induced defect concentrations evolve to dominate the surface structure.The new approach will introduce a powerful framework for bridging multiple time scales in mechanics modeling, making possible accurate mechanics models spanning time scales from femtoseconds to hours. It will also lead to significant advances in understanding ion interactions with semiconductors, which will impact the fields of ion implantation, surface modification, and milling, as well as radiation damage for aerospace and energy applications. The program will also have important educational impact at UIUC and beyond. During the first year of the program, the PI will help establish a student chapter of the Society of Engineering Science (SES) at UIUC and will leverage the 2008 SES conference, being held at UIUC, to help grow the chapter. The student chapter will draw members from undergraduate and graduate students in both mechanical engineering and engineering mechanics.