SusChEM: Collaborative Research: experimental and computational study of structure and thermodynamics of rare earth oxides above 2000 C

SusChEM：合作研究：2000℃以上稀土氧化物结构和热力学的实验和计算研究

• 批准号: 1505657
• 负责人: Axel van de Walle
• 金额: $ 28.56万
• 依托单位: Brown University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2015
• 资助国家: 美国
• 起止时间: 2015-07-01 至 2018-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1505657&HistoricalAwards=false
• 关键词: SusChEM; Collaborative; Research; experimental; computational

NON-TECHNICAL SUMMARY: Materials which are stable to very high temperatures are needed for applications in aerospace, energy, and other technologies. Many such materials contain rare earth oxides, critical materials in potential short supply. Novel experimental and computational methods are studying the structure and stability of such rare earth oxides. The methodology includes diffraction (determination of crystal structure) and calorimetry (measurement of heat effects associated with melting and other reactions) on laser heated samples levitated in a gas stream and not contaminated by contact with other materials, as well as theoretical calculations. Such studies offer a unique opportunity to obtain fundamental understanding of structures, phase transitions, and melting properties and applications to technological problems. The project will also advance general experimental and computational techniques for high temperature research. It will offer opportunities for both undergraduates and graduate students in materials science, chemistry, physics, and engineering to take part in state-of-the-art research in both university and national laboratory settings. TECHNICAL DETAILS: Rare earth oxides are critical materials essential to many important technologies yet their high temperature properties, needed for such applications, are poorly known. Their structure and thermodynamics above 2000°C are being studied using a combination of novel experimental and computational methods. Aerodynamic levitation and laser heating are being used for in situ X-ray diffraction at the Advanced Photon Source, in situ neutron diffraction at the Spallation Neutron Source and for drop calorimetry at the UC Davis Peter A. Rock Thermochemistry Laboratory. Enthalpies of solid state phase transitions and fusion are being measured by calorimetry, and volume changes on phase transitions and thermal expansion of high temperature phases are being determined by diffraction. High temperature thermal analysis complements drop calorimetry. Fusion enthalpies are required for reliable calculations of eutectics of multi-component systems containing rare earths. Ab initio computations of high temperature heat capacities, thermal expansion, and temperatures and enthalpies of phase transitions and fusion are being performed at Brown University using post-density functional theory (DFT) methods, such as hybrid functionals and DFT+U, in conjunction with statistical mechanics techniques such as cluster expansion, lattice dynamics analysis and molecular dynamics. Computed thermal expansion and enthalpies of phase transitions and fusion are being compared to experimental measurements and calculations are being extended to high temperature properties of rare earth oxides not yet accessible experimentally.

非技术摘要：航空航天、能源和其他技术的应用需要在高温下稳定的材料，许多此类材料都含有稀土氧化物，而新的实验和计算方法正在研究这种结构。该方法包括对悬浮在气流中的激光加热样品进行衍射（确定晶体结构）和量热法（测量与熔化和其他反应相关的热效应）。此类研究为获得结构、相变和熔化特性以及技术问题的应用提供了独特的机会。它将为材料科学、化学、物理和工程专业的本科生和研究生提供在大学和国家实验室环境中参与最先进研究的机会：稀土氧化物是。至关重要的关键材料许多重要的技术，但人们对这些应用所需的高温特性却知之甚少，目前正在使用新颖的实验和计算方法来研究它们在 2000°C 以上的结构和热力学。先进光子源的 X 射线衍射、散裂中子源的原位中子衍射以及加州大学戴维斯分校 Peter A. Rock 热化学实验室的液滴量热法固态相变的热函。通过量热法测量相变和聚变，并通过衍射确定高温相的体积变化和滴量热法，以可靠地计算包含的多组分共晶。布朗大学正在使用后密度泛函理论 (DFT) 对高温热容、热膨胀以及相变和聚变的温度和热函进行从头计算。混合泛函和 DFT+U 等方法与团簇展开、晶格动力学分析和分子动力学等统计力学技术相结合，将计算出的热膨胀以及相变和聚变的焓与实验测量进行比较，并且正在扩展计算。稀土氧化物的高温特性尚未通过实验获得。