Theoretical and Experimental Crystal Chemistry

理论与实验晶体化学

• 批准号: RGPIN-2015-04162
• 负责人: Hawthorne, Frank
• 金额: $ 3.64万
• 依托单位: University of Manitoba
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2016
• 资助国家: 加拿大
• 起止时间: 2016-01-01 至 2017-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=612811
• 关键词: Theoretical; Experimental; Crystal; Chemistry

Minerals are the fundamental materials of the Earth, and if we wish to understand the processes which formed the Earth, and which continue to modify its landscape and the human environment, we need to understand the behaviour of minerals under the full spectrum of conditions experienced on Earth. This proposal focuses on a wide variety of minerals in an attempt to understand the atomic-scale factors affecting their constitution and behaviour, and to use this understanding to rationalize and predict their behaviour at the macroscopic scale. I use various forms of radiation (X-rays, neutrons) to 'see' into a mineral at the atomic scale via diffraction, and to derive the arrangement of atoms from which it is built. Details concerning atomic-scale disorder can be seen with spectroscopy using other forms of radiation (e.g. infrared, gamma rays). The resulting atomic-scale details of the mineral give us the information from which we can, in principle, understand aspects of how and at what conditions the mineral formed, and under what conditions it is stable. Why do minerals have the chemical formulae that they do? Why do they have their specific structural arrangements? Why are minerals stable over specific ranges of pH, Eh, temperature, pressure and constituent activities? What are the relations between crystal structure and enthalpy, entropy and Gibbs free energy of formation? How can we derive the atomic-scale mechanisms of geological processes? What is the relation of mathematical complexity to mineral structures and the behaviour of minerals in equilibrium and non-equilibrium processes? These questions are fundamental to Mineralogy itself and yet have tended to be ignored in the past because they are not susceptible to established theoretical techniques in Physics and Chemistry. A major part of this proposal involves the development of a theoretical approach to answer these questions, an approach based on the topology (connectivity) of chemical bonds in space. I will use various aspects of Mathematics (Graph Theory, Combinatorial Topology, Complexity Theory), Physics (Bond-Valence Theory) and Chemistry (the moments approach to the energy density-of-states of solids) to develop connections between patterns of bond connectivity (bond topology) and their energetic content, how these connections dictate the chemical compositions and structural connectivities of minerals, and the ways in which these factors affect how minerals participate in geological processes. This theoretical work is supported by an extensive experimental program of mineral characterization involving amphiboles and tourmalines, a new thrust on gem minerals, TS-block minerals, new minerals, and other diverse projects that can benefit from our local experimental capabilities and theoretical expertise.

矿物是地球的基本材料，如果我们想了解形成地球的过程，并继续改变其景观和人类环境，我们需要了解矿物在地球上经历的各种条件下的行为。该提案侧重于各种各样的矿物，试图了解影响其构成和行为的原子尺度因素，并利用这种理解来合理化和预测其宏观尺度的行为。我使用各种形式的辐射（X射线，中子），通过衍射在原子尺度上“看到”矿物，并推导出原子的排列。有关原子尺度无序的细节可以通过使用其他形式的辐射（例如红外线，伽马射线）的光谱学来观察。由此产生的矿物原子尺度的细节为我们提供了信息，原则上，我们可以从中了解矿物是如何形成的，在什么条件下形成的，以及在什么条件下它是稳定的。为什么矿物有它们的化学式？为什么它们有其特定的结构安排？为什么矿物质在特定的pH值、Eh、温度、压力和组分活性范围内是稳定的？晶体结构与生成焓、生成熵和生成吉布斯自由能之间有什么关系？我们如何推导出地质作用的原子尺度机制？数学复杂性与矿物结构以及矿物在平衡和非平衡过程中的行为有什么关系？这些问题是矿物学本身的基础，但在过去往往被忽视，因为它们不容易受到物理和化学中已建立的理论技术的影响。该提案的一个主要部分涉及开发一种理论方法来回答这些问题，这种方法基于空间化学键的拓扑结构（连接性）。我将利用数学的各个方面（图论，组合拓扑，复杂性理论），物理学（键价理论）和化学（矩接近固体的能量态密度）来建立键连接模式之间的联系（键拓扑）及其能量含量，这些连接如何决定矿物的化学成分和结构连接性，以及这些因素如何影响矿物参与地质过程。这项理论工作得到了广泛的矿物表征实验计划的支持，涉及角闪石和电气石，宝石矿物，TS块矿物，新矿物的新推力，以及其他可以从我们当地的实验能力和理论专业知识中受益的各种项目。