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

“职业：通过从头算法分子模拟计算机辅助设计和发现新型纳米多孔材料”寻找新型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是一个主要的启发式练习。合成这些材料的一个关键组成部分是使用有机模板分子，在特定框架的自组装中充当结构指导剂。我们需要的是一种方法：(1)先验地确定哪些模板分子将合成哪些框架；(2)确定哪些尚未发现的特定框架是可能的。本研究的目的是开发一套计算机工具，以协助发现和合成新型纳米多孔材料，并初步应用这些方法来发现用于燃料电池技术中气体分离和离子传输材料的新型硅酸钛框架。所提出的程序套装将结合两种通用算法：(1)框架-模板匹配，其中使用蒙特卡罗式移动来在给定框架内计算“生长”模板分子；(2)自动框架搜索，其中使用随机搜索方法结合遗传算法来计算搜索可行的晶体框架。为了使分子建模方法起作用，需要对相互作用势能进行适当的计算。为此，已经开发了一种新型的硅酸盐基框架紧密结合处方，该处方比从头算动力学至少快两个数量级，但提供了氧化物键合特性的准确表示。该方法提供了一种快速和准确的方法，将结构完全松弛纳入上述算法中，提供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。该方法将首先应用于合成ETS-4和ETS-10类的二氧化钛骨架，其可行模板尚未确定。ETS-4具有目前用于气体分离技术的热收缩特性。如果找到合适的模板，可以通过指导特定多型的相互生长来潜在地改变这些材料的断裂行为。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。此外，将系统地寻求具有与ETS-4相似特征的新型二氧化钛骨架。本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)将主要基于应用的分子模拟课程纳入本科化学工程课程。目的是使化学工程师熟悉分子模拟方法的实用性和应用，这样他们就可以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。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能力的关键，而合适的数学软件包（如Mathematica）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，该包将强调模型构建的基础知识，并提供可行的Mathematica练习和解决方案，涵盖本科课程。目标是将化学工程问题与提高化学工程教育技术标准的现代数学计算工具相结合。这一发展计划的影响预计将是广泛而深远的，并将潜在地影响到需要材料合成的每个领域，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。这一紧密结合处方本身就代表着沸石及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/模拟界产生影响，特别是在运输、吸附、自组装和成核科学以及沸石同构取代化学等领域。同时，通过将新材料的发现与课堂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项目，通过积极的推广和本科生启蒙，为更大的学术团体服务。

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.