CAREER: Computer-Aided Design and Discovery of Novel Nanoporous Materials Through Ab Initio-Based Molecular Simulation

肯德尔·K·汤姆森·普渡大学《职业生涯：通过从头算分子模拟的计算机辅助设计和发现新型纳米多孔材料》寻找新的纳米多孔材料是一个令人兴奋和活跃的研究领域。然而，尽管进行了深入的研究，发现新的纳米结构框架仍然主要是一种启发式的练习。合成许多此类材料的一个关键成分是使用有机模板分子，这些分子在特定框架的自组装中充当结构导向剂。所需要的是一种(1)先验地确定哪些模板分子将合成哪些框架以及(2)确定哪些特定框架可能尚未被发现的方法。这项研究的目的是开发一套计算机工具来帮助发现和合成新型的纳米多孔材料，并将这些方法初步应用于燃料电池技术中发现用于气体分离和离子传输材料的新型钛硅酸盐骨架。所提出的程序套件将结合两种通用算法：(1)骨架-模板匹配，其中使用蒙特卡罗类运动来计算在给定骨架内生长模板分子；(2)自动骨架搜索，其中使用随机搜索方法和遗传算法相结合来计算搜索可行的晶体骨架。为了使分子模拟方法发挥作用，需要对相互作用势能进行适当的计算。为此，已经开发了一种用于硅酸盐骨架的新的紧密结合配方，该配方至少比从头算动力学快两个数量级，但提供了氧化物成键性质的准确表示。该方法提供了一种快速、准确的方法将完全结构松弛结合到上述算法中，提供了比以前的方法更真实的框架/模板相互作用和结构稳定性确定。该方法将最初应用于合成尚未确定可行模板的ETS-4和ETS-10类钛硅酸盐骨架。ETS-4具有目前在气体分离技术中利用的热收缩特性。如果找到合适的模板，可能会通过指导特定多型体的相互生长来潜在地改变这些材料的断层行为。这可能导致材料具有(1)新颖的收缩性能和(2)增强的离子传输行为，特别适用于燃料电池膜技术。这项拟议的工作还将通过以下活动解决将分子模拟知识库引入化学工程课程的挑战：(1)为化学工程研究生课程开发基于理论和应用的分子模拟课程，以及(2)在本科化学工程课程中纳入一门主要基于应用的分子模拟课程。其目的是使化学工程师熟悉分子模拟方法的实用和应用，以便他们能够与该领域的专家交流，确定分子模拟可能有用的情况，并将这些技术应用于化学工程中的问题。除了分子模拟能力外，化学工程师还应精通一般建模。熟练地分析工程问题、建立工作模型和提取有用信息的能力是有效解决问题的关键，而合适的数学软件包，如数学软件，可以成为有用的教学工具。因此，将开发一个基于网络的学习包，强调通过贯穿整个本科课程的可行的数学练习和解决方案来建立模型的基本原理。其目标是将化学工程问题与现代数学计算工具相结合，提高化学工程教育的技术水平。这一发展计划的影响预计将是广泛和深远的，并可能影响到需要材料合成的所有领域，包括：催化、分离、传感器技术、燃料电池技术、纳米结构热电子材料和纳米级电子器件。这种紧密结合的配方本身代表了分子筛和相关离子氧化物材料的分子模拟向前迈进了一步，并将对沸石/模拟社区产生影响，特别是在传输、吸附、自组装和成核科学以及沸石类象取代化学领域。与此同时，通过将新材料的发现与在课堂上融入模拟方法的教育影响相结合，这些拟议的研究和教育活动提供了一个综合计划，通过积极的拓展和本科生启蒙为更大的学术社区服务。

Kendall K. ThomsonPurdue University"CAREER: Computer-Aided Design and Discovery of Novel Nanoporous Materials Through Ab Initio-Based Molecular Simulation"The search for novel nanoporous materials is an exciting and active field of research. However, despite intensive investigation, discovery of novel nano-structured frameworks remains a mainly heuristic exercise. A key component in synthesizing many of these materials is the use of organic templating molecules that act as structure directing agents in the self-assembly of particular frameworks. What is needed is a means of (1) determining a priori which template molecules will synthesize which frameworks and (2) identifying what specific frameworks are possible that have not yet been discovered. The objective of this research is the development of a suite of computer tools to assist in the discovery and synthesis of novel nano-porous materials, and to initially apply these methods towards the discovery of novel titnaosilicate frameworks for gas separations and ion transport materials in fuel cell technology.The proposed program suite will combine two general algorithms: (1) framework-template matching, in which Monte-Carlo like moves are used to computationally "grow" template molecules within given frameworks, and (2) automated framework search, in which stochastic search methods combined with genetic algorithms are used to computationally search for feasible crystalline frameworks. In order for a molecularmodeling approach to work, a proper accounting of interaction potential energy is required. For this a novel tight-binding prescription for silicate-based frameworks has been developed that is at least two orders of magnitude faster than ab initio dynamics, yet provides an accurate representation of oxide bonding properties. The method provides a fast and accurate means of incorporating full structural relaxation into the abovealgorithms, providing more realistic framework/template interactions and structural stability determination than previous methods.The method will initially be applied to the synthesis of titanosilicate frameworks of the ETS-4 and ETS-10 class, for which viable templates have not been identified. ETS-4 has thermal contraction properties that are currently exploited in gas separation technology. Suitable templates, if identified, could potentially alter the faulting behavior of these materials by directing the inter-growth of specific polytypes. This could result in materials with (1) novel contraction properties and (2) enhanced ion transport behavior, particularly applicable to fuel cell membrane technology. Further, novel titanosilicate frameworks with similar features to ETS-4 will be systematically sought.This proposed work will also address the challenge of bringing the molecular simulation knowledge base to the chemical engineering curriculum through the following activities: (1) development of theory and application based molecular simulation courses for the chemical engineering graduate curriculum, and (2) incorporation of a primarily application based, molecular simulation course in the undergraduate chemical engineering curriculum. The objective is to familiarize the chemical engineer with the utility and application of molecular simulation methods such they can communicate with experts in the field, identify situations where molecular simulation may be useful, and apply the techniques to problems in chemical engineering. In addition to molecular simulation competence the chemical engineer should be proficient in general modeling.The ability to competently analyze an engineering problem, formulate a working model, and extract useful information is key to effective problem solving capabilities, and suitable mathematical packages such as Mathematica can be useful teaching tools. Consequently, a web-based learning package will be developed that will emphasize the fundamentals of model building with workable Mathematica exercises and solutions thatspan the undergraduate curriculum. The goal is to integrate chemical engineering problems with modern mathematical computing tools that raise the technological standards of chemical engineering education.The impact of this development plan is expected to be broad and far reaching and will potentially effect every field where materials synthesis is required, including: catalysis, separations, sensor technology, fuel cell technology, nano-structured thermo-electronic materials, and nano-scale electric devices. The tight-binding prescription in itself represents a step forward in molecular simulation of zeolites and related ionic oxide materials, and will impact the zeolite/simulation community particularly in the areas of transport, adsorption, self-assembly and nucleation science, and zeolite isomorphic substitution chemistry. At the same time, by combining the discovery of new materials with the educational impact of incorporating simulation methods in the classroom, these proposed research and education activities offer an integrated program that serves the greater academic community through aggressive outreach and undergraduate enlightenment.