Thermal Transport in Large Unit Cell Crystals

大晶胞晶体中的热传输

• 批准号: 1507325
• 负责人: Alan McGaughey
• 金额: $ 33万
• 依托单位: Carnegie-Mellon University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2015
• 资助国家: 美国
• 起止时间: 2015-07-01 至 2019-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1507325&HistoricalAwards=false
• 关键词: Thermal; Transport; Large; Unit; Cell

NON-TECHNICAL SUMMARYThis award supports theoretical and computational research and education aimed at achieving a fundamental understanding of how thermal energy is transported in crystals with large unit cells. In a crystalline material, the arrangement of atoms can be described in terms of a unit cell which periodically repeats in all directions to make up the bulk crystal. In some crystals such as gold and silicon, the unit cell contains only a few atoms, while in others, the unit cell may contain upwards of hundreds of atoms. Examples of large unit cell crystals include "zeolites", which have application in catalysis, molecular separation, and gas storage, and "fullerenes", which have applications in molecular electronics and solar energy conversion. Understanding thermal transport in these materials is critical for predicting how they will respond to temperature fluctuations in their surroundings and how they can dissipate excess heat generated during device operation. The way that heat flows through a crystalline material depends on its unit cell. Conventional understanding of thermal transport is based on theory developed for small unit cell crystals. Experimental evidence, however, suggests that these theories are not suitable for modeling thermal transport in large unit cell crystals. The objective of this project is to use atomic-level computational tools to develop a framework for predicting the thermal conductivity of large unit crystals and apply it to zeolites and fullerenes. The results will be of direct importance to scientists and engineers using these materials in everyday applications. The computational tools developed will be suitable for modeling other large unit cell crystals.Through this project, the research team will integrate nanoscience into the undergraduate engineering curriculum at Carnegie Mellon University through a lecture series and distribute the materials through the National Science Foundation-supported nanoHUB. Outreach activities related to large unit cell crystals will be developed and presented to middle school and high school students in Pittsburgh.TECHNICAL SUMMARYThis award supports theoretical and computational research and education aimed at achieving a fundamental understanding of how thermal energy is transported in crystals with large unit cells. Crystalline materials with large unit cells are relevant in a wide range of energy-related challenges and opportunities, such as in catalysis, molecular separation, gas storage, thermoelectric energy conversion, and solar energy conversion. In many of these areas, thermal transport plays a critical role, but has received minimal attention. The central hypothesis of this project is that not all vibrational modes in a large unit cell crystal propagate and that energy transport mechanisms at length scales smaller than the lattice constant are important. The overarching objective is to uncover the underlying physical mechanisms and to suggest strategies for the design of materials with tailored thermal properties.Two distinct materials systems will be considered using a suite of atomic-level computational tools including molecular dynamics simulations and lattice dynamics calculations. First, zeolites, where all atoms are strongly bonded due to covalent and electrostatic interactions will be investigated. Anharmonic and harmonic effects on thermal transport will be rigorously modeled to quantify the contributions of different types of vibrational modes to thermal conductivity. The effects of framework aluminum, non-framework cations, and adsorbed species on thermal conductivity will be quantified. Second, fullerene-based molecular crystals, where the intramolecular interactions are strong but the intermolecular interactions are weak due to van der Waals forces, will be investigated. At low temperatures, a reduced-order model will be developed, while at higher temperatures a network model based on the thermal conductance between molecules will be explored. The modeling predictions will be validated through collaboration with experimental research groups. The methods and tools developed will translate to studies of thermal transport in other large unit cell crystals, such as clathrates, skutterudites, Zintl compounds, gas hydrates, and metal-organic frameworks.Through this project, the research team will integrate nanoscience into the undergraduate engineering curriculum at Carnegie Mellon University through a lecture series and distribute the materials through the National Science Foundation-supported nanoHUB. Outreach activities related to large unit cell crystals will be developed and presented to middle school and high school students in Pittsburgh.

非技术总结该奖项支持理论和计算研究和教育，旨在实现对热能如何在具有大晶胞的晶体中传输的基本理解。 在晶体材料中，原子的排列可以用在所有方向上周期性重复以构成块状晶体的晶胞来描述。 在金和硅等一些晶体中，晶胞仅包含几个原子，而在其他晶体中，晶胞可能包含数百个原子。 大晶胞晶体的实例包括在催化、分子分离和气体储存中具有应用的“沸石”，以及在分子电子学和太阳能转换中具有应用的“富勒烯”。了解这些材料中的热传输对于预测它们将如何响应周围环境的温度波动以及它们如何耗散器件运行期间产生的多余热量至关重要。热量流经晶体材料的方式取决于它的晶胞。传统的理解的热输运是基于理论发展的小单位晶胞晶体。然而，实验证据表明，这些理论是不适合在大的单胞晶体热输运建模。 该项目的目标是使用原子级计算工具来开发预测大单元晶体的热导率的框架，并将其应用于沸石和富勒烯。研究结果将对在日常应用中使用这些材料的科学家和工程师具有直接重要意义。开发的计算工具将适用于模拟其他大型单位晶胞晶体。通过该项目，研究团队将通过系列讲座将纳米科学融入卡内基梅隆大学的本科工程课程，并通过美国国家科学基金会支持的nanoHUB分发材料。与大晶胞晶体相关的推广活动将在匹兹堡开展并向初中和高中学生展示。技术总结该奖项支持理论和计算研究和教育，旨在从根本上理解热能如何在具有大晶胞的晶体中传输。具有大单元电池的晶体材料与广泛的与能源相关的挑战和机遇相关，例如催化、分子分离、气体储存、热电能转换和太阳能转换。在许多这些领域，热传输起着至关重要的作用，但很少受到关注。 该项目的中心假设是，并非所有的振动模式在一个大的单位晶胞晶体传播，能量传输机制的长度尺度小于晶格常数是重要的。总体目标是揭示潜在的物理机制，并建议策略的材料设计与定制的thermalproperty.Two不同的材料系统将被认为是使用一套原子级的计算工具，包括分子动力学模拟和晶格动力学计算。首先，沸石，其中所有原子由于共价和静电相互作用而牢固键合。 热输运的非谐和谐波效应将被严格建模，以量化不同类型的振动模式对热导率的贡献。框架铝，非框架阳离子，和吸附的物种对热导率的影响将被量化。第二，富勒烯基分子晶体，其中的分子内的相互作用是强的，但分子间的相互作用是弱的，由于货车德瓦尔斯力，将进行研究。 在低温下，将开发一个降阶模型，而在较高的温度下，将探索一个基于分子间热导的网络模型。模型预测将通过与实验研究小组的合作进行验证。该研究团队将通过一系列讲座将纳米科学融入卡内基梅隆大学的本科工程课程，并通过美国国家科学基金会支持的nanoHUB分发材料。将开展与大晶胞晶体有关的外联活动，并向匹兹堡的中学生和高中生介绍。