Bridging Length and Time Scales in Catalytic Reaction Systems

调研：动力学蒙特卡罗（KMC）模拟已经成为一个很好的计算工具，从材料生长，催化，DNA/表面相互作用，图像处理，生物化学工程和生物信息学的代谢途径建模等各种问题。 通常，KMC模拟仅限于短的长度和时间尺度，而设备尺寸和形态特征通常涉及更大的空间和时间尺度。 PI一直在开发系统的、分层的粗粒度随机模型，称为粗粒度MC（CGMC），它能够以显著较低的计算成本描述比传统KMC模拟大得多的长度尺度，同时仍然包含微观特征和正确的噪声。 因此，他们提供了一个数学和计算的范例，对许多应用的潜在影响，除了CGMC工具目前不能处理复杂的化学accurately.In这个项目中，PI计划开发必要的多尺度使能技术的表面反应系统。 任务离开现有的技术，并需要一个组合：（a）密度泛函理论的表面反应参数和势能表面的估计，（B）分子动力学模拟表面扩散，（c）新的多级，自适应网格CGMC，和（d）的集成，这种多级CGMC混合多尺度反应器模拟，使建模的现实反应流长度尺度。 这将被应用到模型反应系统和通过高速扫描隧道显微镜（STM）在铂上的氢氧化观察到的时空模式。 智力的优点来自一个反应多尺度框架的发展，将有能力链接微观参数，如分子间的潜力，micrscopkic率，和波动，介观尺度的现象，如时空模式和当地的反应速率。更广泛的影响：粗粒化方法在许多应用中具有潜力，从单个催化剂晶体到用于便携式“绿色”装置的微化学系统，到基于氢的燃料电池，到基于微孔膜的膜反应器，到先进材料制造，到微磁学。 因此，它可以使工业和环境受益。 在教育方面，PI计划（1）开发一个关于介观建模的短期课程，（2）通过网络广泛传播研究材料，并为学生提供教程示例和代码。

Research: Kinetic Monte Carlo (KMC) simulations have emerged as an excellent computational tool for diverse problems ranging from materials growth, to catalysis, to DNA/surface interactions, to image processing, and to modeling of metabolic pathways for biochemical engineering and bio-informatics. Generally, KMC simulations are limited to short length and time scales, while device sizes and morphological features often involve much larger spatial and temporal scales. The PI has been developing systematic, hierarchical coarse-grained stochastic models, referred to as Coarse-Grained MC (CGMC), which are capable of describing much larger length scales than conventional KMC simulations at significantly lower computational cost, while still incorporating microscopic features and the correct noise. They thus provide a mathematical and computational paradigm with potential impact on numerous applications, except that CGMC tools cannot currently handle complex chemistry accurately.In this project the PI plans to develop the necessary multiscale enabling technology for surface reaction systems. The tasks depart from the available technology and entail a combination of: (a) density functional theory for estimation of surface reaction parameters and potential energy surfaces, (b) molecular dynamics to model surface diffusion, (c) novel multilevel, adaptive mesh CGMC, and (d) the integration of this multilevel CGMC in hybrid multiscale reactor simulations to enable modeling of realistic reacting flow length scales. This will be applied to model reaction systems and to the spatio-temporal patterns observed in hydrogen oxidation on platinum via high speed scanning tunneling microscopy (STM). The Intellectual Merit derives from the development of a reaction multiscale framework that will have the ability to link microscopic parameters, such as intermolecular potentials, micrscopkic rates, and fluctuations, to mesoscopic scale phenomena such as spatio-temporal patterns and local reaction rates. Broader Impacts: The coarse-graining methodology has potential in numerous applications, from single catalyst crystals, to microchemical systems for portable, "green" devices, to hydrogen-based fuel cells, to microporous films based membrane reactors, to advanced materials fabrication, to micromagnetics. It can thus benefit industry and the environment. On the educational side, the PI plans to (1) develop a short course on mesoscopic modeling and (2) widely disseminate the research material via the web with tutorial examples and codes for students.