Multiscale Modeling of Compositional Stresses in Nonstoichiometric Oxides

非化学计量氧化物中成分应力的多尺度建模

• 批准号: 1363203
• 负责人: Vivek Shenoy
• 金额: $ 37.41万
• 依托单位: University of Pennsylvania
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2014
• 资助国家: 美国
• 起止时间: 2014-06-01 至 2018-05-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1363203&HistoricalAwards=false
• 关键词: Multiscale; Modeling; Compositional; Stresses; Nonstoichiometric

Oxide materials are of immense importance for energy conversion and energy storage technologies. Their working principle is based on the coupling of transport between ions and electrons. Relevant use includes solid oxide fuel cells, catalysts and electrolyzers, and these effects have also been employed in chemical sensors, electrochemical transducers, and in advanced electronic memories and computing devices. The goal of this work is to define novel computational methods to study how the oxygen vacancies interact with defects such as grain boundaries, dislocations and facets. This will be studied in polycrystalline ceria films used in electronic and energy systems and in nanocrystals used in catalysis, thus influencing functional properties. A large effort and many resources are now being invested to develop efficient methods to improve the catalytic properties and transport in oxide materials. Thus, the insights gained from increased knowledge of defect mechanics at interfaces and grain boundaries could have economic impact, mostly in the energy and electronics industry. Results and methods will be embedded into college and graduate level eductation. Interactive software will be produced to relate mechanics concepts to the broader public.Since the interactions between defects in oxide materials are determined both by atomic-scale phenomena and by the elastic and electrostatic interactions of defects over length scales of hundreds of nanometers, the project will adopt a multiscale approach. The structure of grain boundaries and defects in oxide materials (with ceria as a concrete example) will be predicted using a novel genetic algorithm technique and validated with high-resolution measurements. Based on the structure, this project will study how the formation energies and interaction of defects are influenced by stresses and space charges near the grain boundaries. The distribution of oxygen vacancies and dopants near surfaces and grain boundaries will be determined using a combination of state of the art quantum simulations and a new method to determine the strains of charged defects. Using the information from these atomic-scale simulations, the project will develop a fully-coupled continuum electro-chemo-mechanical model to predict the stresses in polycrystalline oxide films and nanocrystals and to model the influence of stresses on oxygen vacancy density and hence transport. For nanocrystals and polycrystalline films, the project study the effect of stresses on catalytic activity, which will be validated by coulombic calorimetry studies and HRTEM observations. Finally, the fully-coupled electro-chemo-mechanical model will be used to model and predict how strain patterning and defects such as dislocations influence metal-insulator transitions in oxides (with NiO as an example) and the predictions will be validated with experiments. The project will provide an opportunity for graduate and undergraduate students to both carry out experimental work in a leading industrial lab and to develop advanced computational skills. The progress made in the computational methods will be included in the course that the PI has created to promote hands-on simulation experience. Simulation modules enabling the communication of complex mechanics concepts to the broader public will be developed.

氧化物材料对于能量转换和储能技术具有极其重要的意义。它们的工作原理是基于离子和电子之间的耦合传输。相关用途包括固体氧化物燃料电池、催化剂和电解槽，这些效应也已用于化学传感器、电化学换能器以及先进的电子存储器和计算设备。 这项工作的目标是定义新的计算方法来研究氧空位如何与缺陷，如晶界，位错和刻面相互作用。这将在用于电子和能源系统的多晶氧化铈薄膜和用于催化的纳米晶体中进行研究，从而影响功能特性。 目前正在投入大量的努力和资源来开发有效的方法来改善氧化物材料的催化性能和传输。因此，从界面和晶界缺陷力学知识的增加中获得的见解可能会产生经济影响，主要是在能源和电子行业。结果和方法将嵌入到大学和研究生教育中。由于氧化物材料中缺陷之间的相互作用既取决于原子尺度的现象，也取决于数百纳米长度尺度上缺陷之间的弹性和静电相互作用，因此该项目将采用多尺度方法。氧化物材料中的晶界和缺陷的结构（以二氧化铈为具体例子）将使用一种新的遗传算法技术进行预测，并通过高分辨率测量进行验证。本项目将以该结构为基础，研究晶界附近的应力和空间电荷如何影响缺陷的形成能和相互作用。氧空位和掺杂剂的分布附近的表面和晶界将使用最先进的量子模拟和一种新的方法来确定带电缺陷的应变的组合。利用这些原子尺度模拟的信息，该项目将开发一个完全耦合的连续电化学力学模型，以预测多晶氧化物薄膜和纳米晶体中的应力，并模拟应力对氧空位密度的影响，从而传输。对于纳米晶体和多晶薄膜，该项目研究了应力对催化活性的影响，这将通过库仑量热法研究和HRTEM观察来验证。最后，完全耦合的电化学力学模型将用于模拟和预测应变图案化和缺陷（如位错）如何影响氧化物中的金属-绝缘体转变（以NiO为例），并将通过实验验证预测。该项目将为研究生和本科生提供一个机会，既可以在领先的工业实验室进行实验工作，又可以发展先进的计算技能。 在计算方法方面取得的进展将包括在PI为促进实践模拟经验而创建的课程中。将开发模拟模块，以便向更广泛的公众传达复杂的力学概念。