Phase Transitions and the Properties of Liquid Nanoclusters

该奖项是根据2009年美国复苏和再投资法案（公法111-5）资助的。在这个由实验物理化学项目资助的奖项中，Martin Jarrold教授和他的学生将研究具有10-1000个原子的孤立金属纳米团簇的熔化和冻结转变。像融化和冻结这样的相变通常与大块物体有关。这项工作将研究当物体的尺寸缩小到纳米尺寸时会发生什么，在纳米尺寸下，其性质取决于存在多少原子，增加或减少单个原子会产生很大的差异。熔化和冻结跃迁将使用热容测量、离子迁移率测量和捕获离子电子衍射进行研究。这项工作将解决三个主要问题：在多大尺寸上会发生块状融化和冻结转变，特定尺寸的纳米团簇是否会发生过热和过冷，以及液体纳米团簇的性质。假设有100个原子的液态金属团簇，其性质与散装液体非常不同。两项国际合作将为该项目作出贡献。Andres Aguado教授（西班牙巴利亚多利德大学）将进行理论计算，这对理解实验测量结果至关重要。Manfred Kappes教授（Universität Karlsruhe, Germany）将合作使用捕获离子电子衍射来研究中型金属纳米团簇的熔化。这项工作提高了我们对小系统统计热力学的认识，并为实验和计算物理化学的研究生和博士后研究人员提供了良好的培训。

This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5). In this award, funded by the Experimental Physical Chemistry program, Professor Martin Jarrold and his students will study melting and freezing transitions in isolated metal nanoclusters with 10-1000 atoms. Phase transitions like melting and freezing are normally associated with bulk objects. This work will examine what happens when the size of an object is reduced into the nanometer size regime, where the properties depend on how many atoms are present, and adding or subtracting a single atom can make a big difference. The melting and freezing transitions will be investigated using heat capacity measurements, ion mobility measurements, and trapped ion electron diffraction. The work will address three main topics: at what size do bulk-like melting and freezing transitions occur, whether superheating and supercooling occurs for specific sizes of nanoclusters, and the properties of the liquid nanoclusters. A liquid metal cluster with say 100 atoms is expected to have properties that are very different from a bulk liquid. Two international collaborations will contribute to the project. Prof. Andres Aguado (Universidad de Valladolid, Spain) will perform theoretical calculations that are critical to understanding the experimental meaurements. Prof. Manfred Kappes (Universität Karlsruhe, Germany) will collaborate on using trapped ion electron diffraction to investigate the melting of medium-sized metal nanoclusters.This work improves our knowledge of the statistical thermodynamics of small systems, and provides excellent training for graduate and postdoctoral researchers in experimental and computational physical chemistry.