International Collaboration in Chemistry: Origins of the anomalous thermodynamics and dynamics of metastable liquid water

在实验物理化学计划的支持下，康奈尔大学的Abraham Stroock教授和他的研究小组将解决与过冷水和负压水有关的两个悬而未决的问题：1)负压下水的空化机制是什么，2)观察到的过冷水热力学和动力学异常的来源是什么？在过去的几十年里，人们对过冷水表现出许多热力学异常现象进行了广泛的研究：在大气压下-45°C左右的温度下，许多参数（如压缩性、膨胀系数和输运系数）的温度依赖性表明了幂律发散。关于这一现象的一些相互竞争的理论已经出现，但缺乏实验数据使这个问题没有得到解决。该项目将需要在过冷状态下首次测量远离环境压力（正、负）的粘度和张力下的扩散率。Stroock实验室使用的工具包括亚稳汽液平衡（MVLE）、拉曼散射、核磁共振（NMR）和微流控装置技术。Stroock教授的工作将由布里渊散射、声张力和基于光学的密度研究补充，这些研究将在法国高等师范学院物理实验室的Frederic Caupin教授的实验室进行。NSF的提案是根据NSF 08-602：美国研究人员和国外同行之间的化学国际合作（ICC）的招标提交的。水是地球上最重要、研究最多的物质之一，然而，其异常的热力学、动力学和结构性质的起源尚未完全理解。与液态水亚稳态相关的科学研究和技术发展可能对许多领域的研究和技术产生广泛的影响，从植物生理学到分子建模再到制造业。在这个项目中进行的研究不仅可以为新的应用提供基础，还可以提供实验工具，促进这些知识的更广泛的科学和技术影响。丰富的技术组成部分（微加工，光谱学，环境控制）和基本组成部分（热力学，动力学，分子结构）固有的这个项目将提供一个不同寻常的广泛的训练，为学生和博士后参与这项研究。此外，美国和法国团队的初级成员的交换将使这些学生能够全面参与研究，并获得宝贵的接触外国科学和民族文化的机会。这两所pi都有让本科生参与实验室研究项目的良好记录，并将积极招募学生参与该计划。Stroock和他的初级团队成员还将参与K-12教育活动，如在当地科学博物馆举办讲座（例如，树是如何喝水的：亚稳态液体的性质），家庭学校活动，以及由康奈尔NSF-MRSEC运营的教学项目。

In this project, supported by the Experimental Physical Chemistry Program, Professor Abraham Stroock of Cornell University and his research group will address two outstanding questions related to supercooled water and water at negative pressures: 1) What are the mechanisms of cavitation of water at negative pressures, and 2) What are the origins of observed thermodynamic and dynamic anomalies in supercooled water? Supercooled water exhibits a number of thermodynamic anomalies that have been extensively studied for the last decades: the temperature dependence of many parameters (e.g., compressibility, expansion coefficient, and transport coefficients) suggests a power-law divergence, at a temperature around -45°C at atmospheric pressure. A number of competing theories of this phenomenon have emerged, but the lack of experimental data has left the question unresolved. This project will entail the first measurements in the supercooled regime of viscosity away from ambient pressure (both positive and negative) and of diffusivity under tension. The tools utilized by the Stroock laboratory include Metastable Vapor Liquid Equilibrium (MVLE), Raman scattering, nuclear magnetic resonance (NMR), and microfluidic device technology. Professor Stroock's work will be complemented by Brillouin scattering, acoustically generated tension and optics-based density studies performed in the laboratory of Professor Frederic Caupin of the Laboratoire de Physique de l'Ecole Normale Superieure. The NSF proposal leading to this award was submitted in response to solicitation NSF 08-602: International Collaboration in Chemistry between US Investigators and their Counterparts Abroad (ICC).Water is among the most important and most studied substances on earth, yet, the origins of its anomalous thermodynamic, dynamic, and structural properties have eluded complete understanding. Scientific studies and technical developments related to the metastable states of liquid water could have broad impact on research and technology in a number of fields, from plant physiology to molecular modeling to manufacturing. The research conducted in this project may provide not only a fundamental foundation for new applications, but also the experimental tools that can facilitate the broader scientific and technical impacts of that knowledge. The richness of technical components (microfabrication, spectroscopy, environmental controls) and fundamental components (thermodynamics, dynamics, molecular structure) inherent in this project will provide an unusually broad training for students and post-docs involved in this research. Furthermore, the exchange of junior members of the US and French teams will allow these students to engage in the full breadth of the research and gain valuable exposure to a foreign scientific and national culture. Both PIs have a strong track record of involving undergraduates in research projects in their labs, and will actively recruit students to participate in this program. Stroock and his junior team member will also engage in K-12 educational activities such as giving lectures (e.g., How trees drink: the Nature of metastable liquids) at local science museums, home-school events, and teaching programs run by the Cornell NSF-MRSEC.