Phase Transitions in Nanosystems: Effects of Surface, Importance of Fluctuations.

Howard Reiss教授在理论和计算化学项目的支持下，对纳米级系统的相变进行研究。特别强调的是表面效应和波动的作用。理论工具包括热力学、统计力学和密度泛函理论。对于技术上有趣的系统，准确的分子水平知识和/或分子间电位是不可用的，一个增强的液滴模型被开发和应用。这种方法依赖于可测量的宏观热物理量，如表面张力、密度和蒸汽压。正在考虑的问题领域包括团簇成核过程、团簇中的相变、大气气溶胶、局限于纳米孔的流体和流体的毛细凝聚。成核是所有科学技术中最普遍的现象之一。尽管它很重要，但成核理论直到最近都是现象学的。连贯一致的分子成核理论的形成对于大气科学以及纳米孔和介孔材料的许多实际应用具有重要的影响。就前者而言，云滴的凝固与高层大气中的臭氧消耗有关。就后者而言，纳米和介孔系统被用于各种工业过程，如化学分离和封存、吸收材料、催化和石油开采。随着分子筛和纳米管合成的进一步进展，对表面效应的更全面的了解将是必要的。研究生和博士后培训是在研究的同时完成的

Professor Howard Reiss is supported by the Theoretical and Computational Chemistry Program to perform research on phase transitions in nanoscale systems. Particular emphasis is on surface effects and on the role of fluctuations. Theoretical tools include thermodynamics, statistical mechanics and density-functional theory. For technologically interesting systems where accurate molecular-level knowledge and/or intermolecular potentials are unavailable, an enhanced liquid-drop model is developed and applied. This method relies on measurable macroscopic thermophysical quantities such as surface tension, density and vapor pressures. Problem areas under consideration include cluster nucleation processes, phase transitions in clusters, atmospheric aerosols, fluids confined to nanopores, and capillary condensation of fluids. Nucleation is one of the most ubiquitous phenomena in all of science and technology. Despite its importance, the theory of nucleation has until recently been phenomenological. The formulation of a coherent, consistent theory of molecular nucleation has important consequences for many practical applications in atmospheric science and in nanoporous and mesoporous materials. With respect to the former, solidification of cloud droplets is relevant to ozone depletion in the upper atmosphere. With respect to the latter, nano- and meso- porous systems are used in a variety of industrial processes such as chemical separation and sequestration, absorbent materials, catalysis and oil recovery. As further progress is made in synthesis of molecular sieves and nanotubes a more complete understanding of surface effects will be necessary. Graduate and postdoctoral training is accomplished in concert with the research