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

在这个由实验物理化学计划支持的项目中，康奈尔大学的亚伯拉罕·斯特罗克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)过冷水中观测到的热力学和动力学异常的根源是什么？在过去的几十年里，过冷水表现出了许多被广泛研究的热力学反常现象：许多参数(如可压缩系数、膨胀系数和传输系数)的温度依赖性表明，在大气压下的温度约为-45°C时，存在幂定律发散。关于这一现象已经出现了许多相互竞争的理论，但由于缺乏实验数据，这个问题一直没有得到解决。该项目将在远离环境压力(正压和负压)的过冷状态下进行第一次粘度测量，并在张力下测量扩散系数。Stroock实验室使用的工具包括亚稳态气液平衡(MVLE)、拉曼散射、核磁共振(核磁共振)和微流控设备技术。斯特鲁克教授的工作将得到布里渊散射、声学产生的张力和基于光学的密度研究的补充，这些研究是在L师范学院高等物理实验室的弗雷德里克·考平教授的实验室进行的。获得这一奖项的NSF提案是应NSF 08-602：美国研究人员与海外同行在化学方面的国际合作(ICC)的邀请提交的。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不完全清楚。与液态水的亚稳状态有关的科学研究和技术发展可能会对从植物生理学到分子建模再到制造等多个领域的研究和技术产生广泛影响。该项目中进行的研究不仅可以为新的应用提供基本的基础，还可以提供能够促进这一知识产生更广泛的科学和技术影响的实验工具。该项目固有的丰富的技术组件(微制造、光谱学、环境控制)和基本组件(热力学、动力学、分子结构)将为参与这项研究的学生和博士后提供非同寻常的广泛培训。此外，美国和法国团队初级成员的交流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。这两家私人投资机构在让本科生参与其实验室的研究项目方面有着良好的记录，并将积极招募学生参与这一计划。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演讲(例如，树木如何饮酒：亚稳态液体的性质)、家庭-学校活动，以及康奈尔国家科学基金会-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.