Collaborative: Terahertz Spectroscopy of Clathrates

合作：包合物的太赫兹光谱

• 批准号: 2055417
• 负责人: Daniel Mittleman
• 金额: $ 40万
• 依托单位: Brown University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2021
• 资助国家: 美国
• 起止时间: 2021-06-15 至 2024-12-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2055417&HistoricalAwards=false
• 关键词: Collaborative; Terahertz; Spectroscopy; Clathrates

This project funded by the Chemical Structure Dynamics and Mechanism (CSDM-A) program of the Chemistry Division, a collaboration between Professor Daniel Mittleman of Brown University and Professor Michael Ruggiero of the University of Vermont, focuses on the study of the vibrational motions of clathrate materials. Clathrates are porous materials consisting of small molecules, often called ‘guests’, held within a cage formed by a network of ‘host’ molecules. The host molecules can be of many different types, including the crucial example in which the host cage structure is formed by water molecules. These water clathrates can enclose various guest molecules such as methane and other greenhouse gases. Methane clathrates of this type can form naturally in the environment, and are plentiful in the permafrost and at the bottom of the ocean. They are also one of the primary sources of clogs in natural gas pipelines. It is now understood that the vibrational modes of these macromolecular structures, especially those vibrations which oscillate at relatively low frequency, are intimately related to many properties of clathrates including their formation and dissociation dynamics and their chemical reactivity. The collaborative research team is using radiation in the terahertz range of the spectrum (higher frequency than microwaves, but lower than most infrared measurements) to study how these vibrational motions are influenced by temperature, pressure, and the local chemical environment. They are understanding critical chemical reactions involving clathrates, such as the reaction in which an existing guest molecule (e.g., methane) is exchanged with a new one (e.g., carbon dioxide), thus storing the carbon dioxide while extracting the methane. In parallel to these research efforts, the project personnel are coordinating summer workshops for high school students that are offered at both Brown and the University of Vermont, expanding the reach of this research to the next generation of early career scientists. The goal of this research program is to investigate fundamental questions about the kinetics and dynamics that drive the formation and properties of clathrates using terahertz (THz) spectroscopy (0.3 – 4 THz), and to develop a new theoretical framework for interpreting these measurements which accurately accounts for the anharmonicity of the relevant modes. The thermodynamic and structural properties of clathrates are generally well characterized, but the microscopic origins of these macroscopic phenomena remain unknown. As a result, there are many open questions concerning their kinetics of formation and dissociation, vibrational dynamics, structural phase transitions, and stability. This research is employing recently developed techniques for pressure- and temperature-dependent terahertz spectroscopy to characterize the low-frequency modes of various clathrate compounds, and to observe the evolution of the vibrational landscape as reactions such as the guest exchange reaction unfold. The researchers are developing new theoretical tools for the ab initio prediction of these spectra. This approach incorporates a rigorous description of anharmonicity into the vibrational analysis, which is critical for accurately describing the relevant low-frequency modes, as well as many thermodynamic quantities. Finally, the project personnel are also developing a new interdisciplinary course for undergraduate and graduate students covering ultrafast spectroscopy in the chemical sciences, which serves both institutions, as well as the greater STEM community, by filling in this important area of modern chemical research.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

该项目由化学部的化学结构动力学和机制（CSDM-A）计划资助，布朗大学的丹尼尔·米特尔曼教授与佛蒙特大学的迈克尔·鲁吉耶罗教授之间的合作侧重于对杂质材料的振动运动的研究。围墙是由小分子组成的多孔材料，通常称为“客人”，该分子在由“宿主”分子网络形成的笼子中保存。宿主分子可以是许多不同类型的，包括由水分子形成宿主笼结构的关键例子。这些水lates可以包围各种客人分子，例如甲烷和其他温室气体。这种类型的甲烷外裂可以在环境中自然形成，并且在多年冻土和海洋底部都有丰富的形式。它们也是天然气管道中堵塞的主要来源之一。现在可以理解，这些大分子结构的振动模式，尤其是那些在相对较低的频率振荡的振动中，与外lates的许多特性密切相关，包括它们的形成和解离动力学及其化学反应性。协作研究团队正在使用光谱范围的辐射（比微波更高，但低于大多数感染的测量值）来研究这些振动运动如何受温度，压力和当地化学环境的影响。他们正在理解涉及杂质的关键化学反应，例如现有的客体分子（例如甲烷）与新的分子（例如甲烷）（例如二氧化碳）交换，从而在提取甲烷的同时将二氧化碳储存。与这些研究工作的同时，该项目人员是在布朗和佛蒙特大学提供的高中生的协调夏季研讨会，将这项研究的影响范围扩大到了下一代的早期职业科学家。该研究计划的目的是研究有关动力学和动力学的基本问题，这些动力学和动力学使用Terahertz（THZ）光谱（0.3 - 4 THZ）驱动围墙的形成和特性，并开发出一种新的理论框架来解释这些测量值，从而准确地解释了相关模态的非同步模式。围墙的热力学和结构特性通常是很好的特征，但是这些宏观现象的微观起源仍然未知。结果，关于它们的形成和解离，振动动力学，结构相变和稳定性的动力学有许多开放问题。这项研究采用了最近开发的技术依赖压力和温度依赖性的Terahertz光谱，以表征各种杂质化合物的低频模式，并观察振动景观的演变，例如宾客交换反应等反应。研究人员正在开发新的理论工具来从头开始预测这些光谱。这种方法将对非谐度的严格描述纳入振动分析中，这对于准确描述相关的低频模式以及许多热力学量至关重要。最后，该项目人员还正在开发一门新的跨学科课程，以涵盖化学科学中超快光谱的本科和研究生，通过在现代化学研究的这一重要领域中填补这一重要的机构和更大的STEM社区，该奖项通过评估NSF的法规效果而受到评估，该奖项表现出了众所周知的支持。