NSF-EC Cooperative Activity in Computational Materials Research: Bridging Atomistic to Continuum - Multiscale Investigation of Self-Assembling Magnetic Dots During Epitaxial Growth

NSF-EC 计算材料研究中的合作活动：桥接原子与连续体 - 外延生长过程中自组装磁点的多尺度研究

• 批准号: 0502737
• 负责人: Katsuyo Thornton
• 金额: $ 121.8万
• 依托单位: Regents of the University of Michigan - Ann Arbor
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2005
• 资助国家: 美国
• 起止时间: 2005-08-01 至 2010-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0502737&HistoricalAwards=false
• 关键词: NSF; EC; Cooperative; Activity; Computational

This grant is a result of a proposal submitted to the Materials World Net program on NSF-EC Computational Materials Science.Intellectual Merits: In the fabrication of nanostructures for optoelectronic applications, tremendous advances have been realized in the development of self- assembly methods for semiconductor materials based on heteroepitaxial vapor-phase growth techniques. In particular, so-called directed self-assembly methods have been demonstrated recently based on the use of pre-patterned substrates or vertical alignment in growth of multilayers, allowing a high degree of control over size distributions and growth of complex patterned arrays. While tremendous progress has been made for semiconductor systems, self- assembly of metallic nanostructures has not been advanced to the same degree. Such developments offer the potential to revolutionize the development of future media for ultra-high-density magnetic recording. The primary goal of the project is to advance the state of the art in multiscale computational materials science through development of a suite of tools for predictive modeling of directed self- assembly. These tools will be utilized to build fundamental understanding of important microscopic and continuum-level phenomena governing nanoscale self-assembly. Although the computational tools to be developed are general and will have application beyond the systems studied, the feasibility of our approach in applications to specific systems will be demonstrated for the well-studied magnetic material systems Fe/Mo and Fe/W. We propose an integrated approach by joining forces of computational experts from the European Community and the United States, spanning the atomistic to the continuum scales. The work will involve ab initio calculations of surface energies, surface stress, and surface diffusion coefficients, as well as statistical mechanics, mesoscopic and continuum calculations of the evolution of nanostructural morphology and composition of dots during both deposition and annealing, and the resulting self-assembly. By parameter passing, each effort will feed into the other, as the information at the smaller scale will be employed in the larger scale calculations, enabling us to bridge a wide range of length and time scales. Using this approach, we can address questions such as how the interplay between kinetic and thermodynamic effects lead to nanostructural formation and what controls the spatial and size distributions of the dots. Answers to these questions are not only of fundamental interest but also allow us to provide insights into processes that produce large-scale self-organized arrays of magnetic dots. To fulfill these specific tasks, we combine modern computational tools, like phase-field models, homogenization techniques and asymptotic expansions with state- of-the-art computational methods, such as multigrid solvers, adaptive and composite finite elements and parallel kinetic Monte Carlo simulations. Furthermore, in collaboration with an experimental partner in EU, the models will be subjected to sharp and intensive tests and validation on the model systems.Broader Impacts: The major impacts on the community at large are two-fold: (1) New intensive summer courses on crystal and epitaxial growth for gifted high school students in both US and Europe, and (2) managed and conscientious effort by every one of the PIs to include undergraduate and graduate students with diverse backgrounds in this project. The US summer school will be offered in cooperation with the California State Summer School for Mathematics and Science (COSMOS) at the University of California, Irvine and will be planned and taught by all of the PIs in the US. The EC counterpart will also offer a similar program at CEASAR. Several of the PIs have experience with planning and executing such programs. To ensure diversity in recruitment, one of the PIs (Thornton) will be in charge of contacting high school teachers and researchersat targeted schools directly to identify talents in under-represented groups. In addition, PIs will attend and judge local science fairs at the high school level and utilize such forums as a ground for outreach activities.

这项资助是由于提交给材料世界网络计划的NSF-EC计算材料科学。智力优点：在制造纳米结构的光电应用，巨大的进步已经实现了在半导体材料的自组装方法的发展异质外延气相生长技术的基础上。 特别地，最近已经证明了所谓的定向自组装方法，其基于在多层的生长中使用预图案化衬底或垂直对准，允许高度控制复杂图案化阵列的尺寸分布和生长。 虽然半导体系统已经取得了巨大的进展，但金属纳米结构的自组装尚未发展到相同的程度。这些发展有可能彻底改变未来超高密度磁记录介质的发展。 该项目的主要目标是通过开发一套用于定向自组装预测建模的工具来推进多尺度计算材料科学的最新技术水平。 这些工具将被用来建立重要的微观和连续水平的纳米级自组装现象的基本理解。 虽然要开发的计算工具是通用的，并将有超出系统研究的应用程序，我们的方法在特定系统的应用程序的可行性将被证明为良好的研究磁性材料系统Fe/Mo和Fe/W。 我们提出了一个综合的方法，从欧洲共同体和美国的计算专家的联合力量，跨越原子的连续尺度。这项工作将涉及从头计算的表面能，表面应力和表面扩散系数，以及统计力学，介观和连续计算的纳米结构形态和组成的点在沉积和退火过程中的演变，以及由此产生的自组装。 通过参数传递，每一个努力将反馈到另一个，因为较小尺度的信息将用于较大尺度的计算，使我们能够桥接广泛的长度和时间尺度。 使用这种方法，我们可以解决诸如动力学和热力学效应之间的相互作用如何导致纳米结构的形成以及是什么控制了点的空间和尺寸分布等问题。 这些问题的答案不仅具有根本意义，而且还使我们能够深入了解产生大规模自组织磁点阵列的过程。为了完成这些特定的任务，我们结合联合收割机现代计算工具，如相场模型，均匀化技术和渐近展开与国家的最先进的计算方法，如多重网格求解器，自适应和复合有限元和并行动力学蒙特卡罗模拟。此外，我们会与欧盟的一个实验伙伴合作，对模型系统进行严格和密集的测试和验证。更广泛的影响：对整个社会的主要影响有两方面：（1）为美国和欧洲有天赋的高中生提供关于晶体和外延生长的新暑期强化课程，以及（2）每一位PI都在管理和认真努力，以将具有不同背景的本科生和研究生纳入本项目。 美国暑期学校将与加州大学欧文分校的加州州立数学与科学暑期学校（COSMOS）合作提供，并将由美国所有的PI策划和授课。欧共体对口单位也将在CEASAR提供类似的方案。 几位PI具有规划和执行此类计划的经验。 为了确保招聘的多样性，其中一名PI（桑顿）将负责直接联系目标学校的高中教师和研究人员，以确定代表性不足的群体中的人才。 此外，私人研究员将参加和评判高中一级的地方科学博览会，并利用这些论坛作为外联活动的基础。