Geometric Frustration in Isomerizations of Magic Sized Clusters

在化学系大分子、超分子和纳米化学(MSN)计划的支持下，康奈尔大学的Robinson教授和Dshemuchadse教授正在探索纳米簇中的原子组织--少数原子分子和较大晶体之间缺失的环节--如何改变，仅仅取决于它们的大小。从纳米粒子到日常散装材料，大多数材料的原子排列都是已知的。但对于比纳米粒子更小的纳米团簇来说，表面效应对原子结构的稳定性有很大影响。用实验技术和计算机模拟研究了幻数大小团簇中原子稳定性的起源。对纳米团簇结构的详细控制，以及精确操纵从一种原子排列到另一种原子排列的明确和快速转换的能力，可能会在光通信、能量收集或量子计算中应用。Dshemuchadse教授和她的团队正在致力于纳米颗粒生长模拟的可视化，以互动教育在线材料的形式向公众提供。此外，Robinson教授和Dshemuchadse教授正在设计一个关于晶体结构的演示工具包，它为美国各地的K-12教师说明了指导材料结构的有序原则。该项目的目标是确定无机纳米团簇和纳米粒子中原子有序和异构化之间的关系。在硫化镉中，观察到了具有非常特殊的原子排列的纳米团簇，这些纳米团簇具有所谓的“魔术”大小，可以改变它们的结构。当硫族镉化合物被合成成离散的团簇大小，形成所谓的“魔术大小的纳米团簇”时，它们能够在两个不同的结构之间连贯地转换，或异构化。这个项目正在研究由原子结构排列引起的几何挫折感，以及这种挫折感如何影响异构化。这种行为的起源正在通过纳米团簇合成和合成后修改，以及模拟不同团簇构型的稳定性的蒙特卡罗模拟来实验研究。了解并能够控制纳米粒子中从局域团簇行为到块状晶体行为的可逆交叉，可以导致无机材料经历旨在切换或传感行为的固-固转变，这将在能量收集或量子计算中找到应用。该团队正在通过创建自组装模拟的可视化并提供互动的在线材料，使公众能够接触到纳米科学。他们还在为借阅图书馆模块设计一个关于晶体结构及其与材料性质关系的教育演示工具包。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

With support from the Macromolecular, Supramolecular and Nanochemistry (MSN) Program in the Division of Chemistry, Professors Robinson and Dshemuchadse at Cornell University are exploring how the atomic organization in nanoclusters—the missing link between few-atom molecules and larger crystals—can change, depending solely on their size. The atomic arrangement of most materials, from nanoparticles to everyday bulk materials, is known. But for nanoclusters, which are smaller than nanoparticles, surface effects can have a large influence on the stability of the atomic structure. The origin of the atomic stability in magic-sized clusters is investigated with experimental techniques and computer simulations. The detailed control of nanocluster structures and the ability to precisely manipulate the defined and rapid changeover from one atomic arrangement to another could have applications in optical communications, energy harvesting, or quantum computing. Professor Dshemuchadse and her group are working on the visualization of nanoparticle growth simulations to be made available to the public as interactive educational online materials. Additionally, Professors Robinson and Dshemuchadse are designing a demonstration kit on crystal structures, which illustrates the ordering principles that govern the structure of materials for K-12 teachers across the US.The objective of the project is to determine the relationship between the atomic ordering and isomerization in inorganic nanoclusters and nanoparticles. In cadmium sulfide, nanoclusters of very specific atomic arrangements of so-called "magic" sizes have been observed to transform their structure. When cadmium chalcogenides are synthesized into discrete cluster sizes, forming so-called "magic-sized nanoclusters", they are able to coherently transform between two distinct structures, or isomerize. This project is investigating the geometric frustration induced by the atomic structural arrangements, and how the frustration may influence isomerizations. The origin of this behavior is being investigated experimentally through nanocluster synthesis and post-synthetic modifications, as well as Monte-Carlo simulations to model the stability of different cluster configurations. Understanding and being able to control the reversible crossover from local-cluster to bulk-crystalline behavior in nanoparticles can lead to inorganic materials undergoing solid-solid transitions designed for switching or sensing behavior, which can find application in energy harvesting or quantum computing. The team is making nanoscience accessible to the public by creating visualizations of self-assembly simulations and providing interactive online materials. They are also designing an educational demonstration kit on crystal structures and their relationship with materials properties for lending library modules.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.