Functionality from local structure in conventional and hybrid Prussian blues

金属-有机骨架材料是一类金属离子通过有机连接物连接成网络的材料，在过去的二十年里，由于其结构和功能性质的多样性而引起了全世界的关注。然而，这些材料的开发速度远远超出了我们完全理解它们行为的能力。这项研究项目将侧重于普鲁士蓝类似物，这是金属有机框架更广泛家族中的一组特别简单和优雅的材料，但显示了广泛的科学有趣和技术相关的功能。对这些材料的详细研究不仅对它们本身有很大的兴趣，而且还将为更好地理解更复杂的结构铺平道路。普鲁士蓝结构是一种看似简单的离子排列，以形成由相互关联的“笼子”组成的晶格。许多不同的分子构件可以排列在相同的基本结构中：因此，尽管人们已经知道它很多年了，但这种类型的新材料仍在不断被发现。明智地选择正确的组件可以使材料具有许多显著的性能。其中包括多铁性，其中磁和电有序相互关联，导致在计算中的应用；光磁体，其磁行为在光照射下改变；以及多孔材料，能够从其环境中吸收气体或金属离子。构建块可以很容易地互换，这使得这是一个非常有希望的定向材料设计系统：如果我们能够预测任何给定的组分将对材料的性能产生的影响，我们将能够设计出具有给定应用所需的性能的材料。然而，为了理解组成和功能之间的联系，我们必须了解两者是如何与材料的结构相关的。从历史上看，用来确定材料结构的结晶学方法给出了关于每个原子平均位置的非常准确的信息，但只是间接地表明了结构在局部可能偏离平均位置有多远。然而，全散射实验对材料的局部结构和平均结构都很敏感。使用逆蒙特卡罗算法分析这些实验可以产生一个同时揭示局部结构和平均结构的晶体结构模型，从而导致对这些材料前所未有的了解。本研究计划将调查四组精心挑选的普鲁士蓝结构材料。利用总中子和X射线散射与计算机模拟相结合的方法，将考虑三个特定的局部特征对这些材料功能的影响。了解这些特征和材料性能之间的联系将是设计这一家族中具有特定功能的新材料的重要一步，从而有助于更全面地了解金属-有机骨架材料。

The family of metal-organic framework materials, in which metal ions are connected together into a network by organic linkers, has attracted worldwide attention over the past two decades for its diversity of both structures and functional properties. Yet these materials are being developed at a rate that far exceeds our ability to fully understand their behaviour. This research project will focus on the Prussian blue analogues, a particularly simple and elegant group of materials within the broader family of metal-organic frameworks that nonetheless displays a wide range of scientifically interesting and technologically relevant functionalities. As well as being of great interest in their own right, detailed studies of these materials will thus pave the way towards greater understanding of more complex structures.The Prussian blue structure is a deceptively simple arrangement of ions to form a crystal lattice consisting of interlinked "cages". Many different molecular building blocks can be arranged in the same basic structure: thus although it has been known for many years, new materials of this type continue to be discovered. Judiciously selecting the right components can lead to materials with many remarkable properties. These include multiferroics, in which magnetic and electric ordering are interlinked, leading to applications in computing; photomagnets, whose magnetic behaviour changes when illuminated with light; and porous materials able to absorb gases or metal ions from their environment.The ease with which the building blocks can be interchanged makes this a highly promising system for targeted materials design: if we can predict the effect any given component will have on a material's properties, we will be able to engineer a material with precisely the properties needed for a given application. In order to understand the link between composition and functionality, though, we must understand how both are related to the material's structure. Historically, the crystallographic methods used to determine the structure of materials have given very precise information about the average position of each atom, but only indirect indications of how far the structure might locally deviate from that average. However, total scattering experiments are sensitive to both the local and average structures of a material. Analysing these experiments using the reverse Monte Carlo algorithm can produce a model of the crystal structure that simultaneously reveals both the local and average structures, leading to an unprecedented understanding of these materials.This research programme will investigate four carefully selected sets of materials with the Prussian blue structure. Using a combination of total neutron and X-ray scattering with computer simulation, the effects of three specific local features on these materials' functionality will be considered. Understanding the link between these features and the material properties will be an important step towards designing new materials in this family with specific functionality tuned to particular applications, and in turn towards a more comprehensive understanding of metal-organic framework materials in general.