Collaborative Research: CDS&E: Experimentally verified nano-oxidation simulations of Cu surfaces

关于宏观尺度上金属表面氧化的知识很多，但是对于这个过程是如何在最小的分子尺度上开始的却知之甚少。了解发生在纳米（一米的十亿分之一）长度尺度上的氧化现象在科学和技术上都很重要，因为越来越多的材料被设计成纳米尺度用于实际应用。这种纳米级材料的稳定性不能直接从它们的体积对应物的知识中推断出来，并且需要新的理论来预测这种小尺度的材料性质。这个合作项目汇集了一个理论化学家，他将模拟铜表面氧化的单个反应机制，一个理论物理学家，他将把这些机制结合在氧化物生长动力学的统计模型中，最后是一个实验显微镜学家，他可以用电子显微镜观察纳米级氧化岛的生长。这个研究小组将共同努力，从原子尺度上了解铜表面的初始氧化。作为这项工作的一部分，将开发新的模拟方法。将开发和用于模拟氧化的软件将免费发布给其他研究人员和公众。这些技术也将被纳入研究生课程，并作为德克萨斯州奥斯汀市和宾夕法尼亚州匹兹堡市高中推广项目的一部分。该奖项支持匹兹堡大学和德克萨斯大学奥斯汀分校之间的合作研究和教育工作，以开发可用于模拟纳米氧化的材料计算工具，并将计算预测与实验观察相关联。pi将集成用于表面动力学建模的通用代码，并解决提出的研究中的三个关键挑战，即(i)使用加速动力学方法和具有经验势和密度泛函理论的离晶格自适应动力学蒙特卡罗（KMC）来提取表面氧化的反应机制，（ii）继续发展薄膜氧化KMC方法，特别是将其从2维扩展到3维。（iii）开发一种粗粒化方法，对自适应KMC发现的反应机制表示进行粗粒化，为三维薄膜氧化代码提供事件表。这些研究将为薄膜氧化模拟提供现实的输入参数，允许对成核行为，纳米氧化和聚并过程中氧化岛的形态演变进行关键的见解，并提供理解岛稳定性所需的表面和界面能量。这项合作建立在现有的基础设施上，包括匹兹堡的实验电子显微镜工作以及奥斯汀和匹兹堡的理论和软件工作。这个研究小组将共同努力，从原子尺度上了解铜表面的初始氧化。用于模拟氧化过程的软件将免费发布给其他研究人员和公众。这些技术也将被纳入研究生水平的课程，并作为奥斯汀和匹兹堡高中推广项目的一部分。

NON-TECHNICAL SUMMARYThere is a great deal of knowledge about the oxidation of metal surfaces on macroscopic scales, but very little is known about how the process starts at the smallest molecular scales. Understanding the oxidation phenomena that occur at such nanometer (one billionth the size of a meter) length scales is of both scientific and technological importance, since more and more materials are being engineered at nanometer scales for practical applications. The stability of such nanoscale materials cannot necessarily be inferred directly from the knowledge about their bulk counterparts, and new theories are needed to predict material properties at such small scales. This collaborative project brings together a theoretical chemist who will model the individual reaction mechanisms of the oxidation of a copper surface, a theoretical physicist who will combine these mechanisms in a statistical model of the oxide growth kinetics, and finally an experimental microscopist who can watch the growth of nanometer scale oxide islands with an electron microscope. This research team will work together to understand the initial oxidation of copper surface, from the atomic scale on and up. New simulation methodologies will be developed as part of this effort. The software that will be developed and used to model the oxidation will be released freely to other researchers and to the public. The techniques will also be incorporated into graduate-level courses and as part of high-school outreach programs both in Austin, TX and Pittsburgh, PA. TECHNICAL SUMMARY This award supports a collaborative research and education effort between the University of Pittsburgh and the University of Texas at Austin for developing materials computational tools that can be used to model nano-oxidation, and to correlate computational predictions with experimental observations. The PIs will integrate versatile codes for modeling dynamics at surfaces and address three key challenges in the proposed research, which are (i) to use accelerated dynamics methods and off-lattice adaptive kinetic Monte Carlo (KMC) with empirical potentials and density functional theory to extract the reaction mechanisms of surface oxidation, (ii) to continue the development of the Thin Film Oxidation KMC approach, particularly taking it from 2 to 3 dimensions, and (iii) to develop a method for coarse graining the representations of reaction mechanisms found with adaptive KMC to provide the event tables for the three-dimensional Thin Film Oxidation code. These studies will provide realistic input parameters for the Thin Film Oxidation simulations, allow for critical insights to be made into the nucleation behavior, morphological evolution of oxide islands during nano-oxidation and coalescence, and provide the surface and interface energies required to understand island stability. This collaboration builds on existing infrastructure, including the experimental electron microscopy effort in Pittsburgh and the theoretical and software efforts in Austin and Pittsburgh. This research team will work together to understand the initial oxidation of a copper surface, from the atomic scale on and up. The software that will be used to model the oxidation will be released freely to other researchers and to the public. The techniques will also be incorporated into graduate-level courses and as part of high-school outreach programs both in Austin and Pittsburgh.