Materials World Network: First-Principles-Based, Large-Scale Modeling of Nanostructural Evolution Binary Alloys

该奖项支持美国和德国的研究人员在材料建模方面正在进行的国际合作。这项工作的目的是在第一性原理输入和大规模模拟的基础上模拟和理解合金中特征纳米团簇的演变，即所谓的沉淀。德国Erlangen的S.Mueller的研究小组以其对材料的低维方面的兴趣和开发表面的团簇展开(CE)方法而闻名。哈特的研究小组在研究空位有序化合物方面有经验，开发了广泛的CE方法学，并成功地进行了本科生研究计划。该项目建立在前一个奖项NSF-0244183和DFG-MU1648/3开始的PI之间的国际合作的基础上。在该项目下，PI开发了一种进化方法(即遗传算法)来构建哈密顿模型；以惊人的精度模拟了铜-钯系统复杂的一维和二维超结构；研究了过渡金属(TM)碳化物和氮化物中的空位有序系统，发现了与TM硫族化合物的惊人联系；研究了难熔的bcc化合物。到目前为止，私营部门各小组的优势互补，形成了对项目成功至关重要的协同作用。此外，该项目及其合作支持了几名研究生，并利用G.Hart对本科生研究的坚定承诺，为近12名本科生提供了机会，其中包括几名来自代表性不足群体的参与者。在前两年工作的基础上，PI将把他们的方法扩展到大规模的沉淀演化模拟；模拟沉淀成核、生长和成熟；模拟空位有序。在这个项目中，他们将：1.开发更高级的动力学和热力学蒙特卡罗程序，并研究fcc、bcc和hcp基金属合金中的析出。这包括非布拉维晶体的延伸(见第三点)。将现有的用于优化合金构型的遗传算法方法(例如基态搜索)扩展到模拟可探索更大搜索空间的细胞无关模型。3.开发建立在扩展的团簇展开形式基础上的新代码，并研究非布拉韦晶体系统(例如，六方密排系统)，包括首次在这些系统中显式处理远程应变效应。该项目的更广泛的影响包括：1.首次可以探索多种重要的合金类型，而不仅仅是立方体系统。处理HCP系统的能力为镁基和钛基金属间化合物系统以及一大类纤锌矿基III-V和II-IV半导体材料打开了大门。这些扩展的方法和代码将免费提供给其他研究人员，包括用于构建模型哈密顿量和搜索晶体结构的遗传算法。3.继续为本科生，特别是来自代表性不足群体的本科生提供研究经验和一对一的教师指导。美方的合作非常成功地将本科生的研究经验融入到项目和合作中。该奖项由美国国家科学基金会国际科学与工程办公室的欧洲项目共同资助。

This award supports an ongoing international collaboration in materials modeling between researchers in the US and in Germany. The aim of this work is to model and understand the evolution of characteristic nanoclusters, so-called precipitates, in alloys based on first-principles input and large-scale simulations. The research group of S. Mueller in Erlangen, Germany, is noted for its interest in low-dimensional aspects of materials and developing a cluster expansion (CE) methodology for surfaces. The research group of G. Hart has experience in studying vacancy-ordering compounds, extensive CE methodology development, and a successful undergraduate research program. The project builds on the international collaboration between the PIs that started with their previous award, NSF-0244183 and DFG-MU1648/3. Under that project the PIs developed an evolutionary approach (i.e., genetic algorithm) for constructing model Hamiltonians; modeled the difficult one-dimensional and two-dimensional superstructures of the Cu-Pd system with remarkable accuracy; studied vacancy-ordering systems in transition-metal (TM) carbides and nitrides, finding a surprising connection to TM chalcogenides; studied refractory bcc compounds. The complementary strengths of the PIs respective groups create a synergy which has been essential to the success of the project so far. Additionally, the project and its collaboration have supported several graduate students and leveraged G. Hart's strong commitment to undergraduate research, providing opportunities for almost a dozen undergraduate students, including several participants from underrepresented groups. Building on the first two years' work, the PIs will extend their methodology to large-scale modeling of precipitate evolution; modeling precipitate nucleation, growth, and ripening; modeling vacancy ordering. During this project, they will:1. Develop further advanced kinetic and thermodynamic Monte Carlo codes and study precipitation in fcc-, bcc-, and hcp-based metal alloys. This includes an extension to non-Bravais crystals (see point 3.).2. Extend existing genetic algorithm approaches for optimizing alloy configurations (e.g., groundstate searches) to simulation cell-independent models that can explore larger search spaces. 3. Develop new codes built on an extended cluster expansion formalism and study non-Bravais crystal systems (e.g., hexagonal-close-packed systems), including an explicit treatmentof long-range strain effects for the first time in these systems. The broader impacts of the project include:1. For the first time, a large range of important alloy types can be explored, not just cubic systems. The ability to treat hcp systems opens the door to Mg-based and Ti-based intermetallic systems and the large class of wurtzite-based III-V and II-IV semiconductor materials.2. These extended methods and codes will be freely available to other researchers, including thegenetic algorithms for model Hamiltonian construction and searching crystal structures. 3. Continue to provide undergraduate students, especially those from underrepresented groups,with research experience and one-to-one faculty mentoring. The US side of the collaborationhas very successfully integrated undergraduate research experiences into the project and the collaboration. Students are involved long-term, from project inception to final publication.This award is co-funded by the Europe program of the NSF Office of International Science and Engineering.