Geometric Frustration in Isomerizations of Magic Sized Clusters

在化学系大分子、超分子和纳米化学（MSN）项目的支持下，康奈尔大学的罗宾逊教授和Dshemuchadse教授正在探索纳米团簇中的原子组织--少原子分子和大晶体之间缺失的一环--如何改变，这仅仅取决于它们的大小。大多数材料的原子排列，从纳米颗粒到日常的块状材料，都是已知的。但是对于比纳米颗粒小的纳米团簇，表面效应可以对原子结构的稳定性产生很大的影响。利用实验技术和计算机模拟研究了魔大团簇中原子稳定性的起源。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定义和快速转换的能力可能在光通信，能量收集或量子计算中有应用。Dshemuchadse教授和她的团队正在研究纳米颗粒生长模拟的可视化，并将其作为交互式教育在线材料提供给公众。此外，罗宾逊教授和Dshemuchadse正在设计一个关于晶体结构的演示工具包，该工具包为美国K-12教师说明了控制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颗粒中原子有序和异构化之间的关系。在硫化镉中，已经观察到具有所谓的"神奇"尺寸的非常特定的原子排列的纳米团簇改变其结构。当镉硫族化物被合成为离散的簇尺寸时，形成所谓的“魔法尺寸的纳米簇”，它们能够在两种不同的结构之间进行相干转换，或者异构化。本计画研究原子结构排列所引起的几何挫折，以及这种挫折如何影响异构化反应。这种行为的起源正在研究实验通过纳米团簇合成和合成后的修改，以及蒙特-卡罗模拟模拟不同的集群配置的稳定性。理解并能够控制纳米颗粒中从局部簇到体晶行为的可逆交叉可以导致无机材料经历专为开关或传感行为而设计的固-固转变，这可以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和提供交互式在线材料，使公众可以访问纳米科学。 该奖项反映了NSF的法定使命，并通过使用基金会的知识价值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.