Novel Vibrational Modes and Thermal Properties in Systems with Large, Open Unit Cells

大型开放单元系统中的新颖振动模式和热性能

• 批准号: 0071863
• 负责人: Frank Bridges
• 金额: $ 30万
• 依托单位: University of California-Santa Cruz
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2000
• 资助国家: 美国
• 起止时间: 2000-06-01 至 2004-05-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0071863&HistoricalAwards=false
• 关键词: Novel; Vibrational; Modes; Thermal; Properties

This individual investigator award is to a senior professor at the University of California in Santa Cruz. The project involves a series of local structure (XAFS) measurements on systems whichhave large, open unit cells. Such materials have a rich array of vibrational motions, many of which are not observed in simple structures. In particular, there can be a large number of low energy optical phonon modes, some of which involve rotations of nearly rigid atomic. Such rigid unit vibrational modes have been proposed explain the novel negative thermal expansion coefficient of ZrW2O8 and other open structures. Another set of open structure materials are the partially filled skutterudite compounds. Here rare earth atoms can be incorporated into a void in the unit cell and strongly suppress the thermal conductivity. The XAFS measurements will clarify whether the proposed structural models are correct and provide a basis for developing better thermoelectric compounds and low thermal expansion materials. The work will provide educational opportunities for both graduate and undergraduate students to work as a team under the PI. Students will gain experience working at a national facility as well as learn experimental design and data analysis at the home institution, UCSC. %%%A number of complex materials, containing open spaces within the crystal structure, exhibit unusual thermal properties. They are potentially important for a variety of practical applications, including better thermoelectric coolers and materials that do not shrink when cooled.The voids in such materials allow the atoms to vibrate in new ways and many of the unusual and enhanced thermal properties are attributed to such motions. In one set of materials, clusters of atoms are thought to vibrate nearly as a single unit; in others it has been proposed thateach added impurity atom "rattles around" inside a void in the structure. This is an individual investigator award to a senior professor at the University of California at Santa Cruz to fund the detailed experimental measurements of these types of motion crucial for developing an understanding of these unusual thermal properties. The work will provide educational opportunities for both graduate and undergraduate students to work as a team under the PI. Students will gain experience working at a national facility as well as learn experimental design and data analysis at the home institution, UCSC. ***

这个个人研究奖是给圣克鲁斯的加州大学的一位高级教授的。 该项目涉及一系列的局部结构（XAFS）测量系统whichhave大，开放的单位细胞。这些材料具有丰富的振动运动，其中许多是在简单结构中观察不到的。特别是，可以有大量的低能光学声子模式，其中一些涉及近刚性原子的旋转。这种刚性单元振动模式的提出解释了ZrW_2O_8和其他开放结构的新颖的负热膨胀系数。另一组开放结构材料是部分填充的方钴矿化合物。在这里，稀土原子可以掺入到晶胞中的空隙中，并强烈抑制热导率。XAFS测量将澄清所提出的结构模型是否正确，并为开发更好的热电化合物和低热膨胀材料提供基础。这项工作将为研究生和本科生提供教育机会，作为PI下的团队工作。学生将获得在国家设施工作的经验，并在家庭机构UCSC学习实验设计和数据分析。许多复杂的材料，在晶体结构中含有开放空间，表现出不寻常的热性能。它们对于各种实际应用都有潜在的重要性，包括更好的热电冷却器和冷却时不收缩的材料。这些材料中的空隙允许原子以新的方式振动，许多不寻常的和增强的热性能都归因于这种运动。在一组材料中，原子团被认为几乎是作为一个单一的单元振动;在另一些材料中，人们提出，每个添加的杂质原子都在结构中的空隙中“嘎嘎作响”。这是一项个人研究奖，授予位于圣克鲁斯的加州大学的一位资深教授，以资助对这些运动类型的详细实验测量，这些运动类型对于了解这些不寻常的热特性至关重要。 这项工作将为研究生和本科生提供教育机会，作为PI下的团队工作。学生将获得在国家设施工作的经验，并在家庭机构UCSC学习实验设计和数据分析。***