Hydrous Components in Nominally Anhydrous Phases

氢作为一种次要成分存在于许多结晶物质中，作为水分子和氢氧离子，即所谓的含水成分。含有这些成分的矿物包括构成地球和具有重要技术意义的合成工业类似物的矿物。地球矿物中的氢占地球氢的绝大部分，对地球内部的行为有着深远的影响。类似地，含水成分可以显著地改变合成材料的材料特性，例如半导体。尽管氢在这些情况下具有明显的重要性，但仍然存在两个基本的不确定性：1)氢在晶体结构中的位置以及2)氢存在的浓度。这项工作将通过实验室实验和计算机模拟的综合方法来解决这两个问题。这将包括氢探测分析技术的发展，详细的光谱研究，以及量子力学计算实验数据的解释。除了继续研究先前研究过的硅酸盐矿物（地球上最丰富的矿物）外，研究还将重点放在二元氧化物矿物上。二元氧化物不仅在地质学上具有相关性，而且在许多成熟的和新兴的技术中也具有极大的相关性，从太阳能电池到激光、触摸屏、颜料、半导体和平面屏幕显示。氢杂质已被证明在这些环境中起着关键作用。因此，这项研究不仅对了解我们星球的内部运作很重要，而且对新技术的发展也很重要。人们早就认识到，名义上无水矿物（NAMs）中的含水成分（OH-和H2O）在地球科学中具有重要意义。这些相，包括丰富的地幔相，如橄榄石、石榴石、辉石和环woodite，可能是地球上最大的氢储集层。NAMs中的微量氢通常会对其材料性能产生巨大的影响，从熔点到机械变形、导热性和导电性、颜色、辐射稳定性。尽管氢在NAMs中的重要性很明显，但仍然存在两个基本问题。首先是这些相中氢浓度的定量。在过去的几十年里，已经尝试或利用了许多技术，包括核剖面分析和SIMS测量，但与测量NAMs中痕量氢浓度相关的技术挑战已被证明难以克服。其次是NAMs中特定氢位点的识别。虽然在特定的NAMs（如石榴石）中已经确定了一些缺陷位置，但在大多数阶段中，很少有资源可以建立详细的缺陷结构。我们对这些问题提出的解决方案是一种综合的方法，考虑了测量矿物中痕量氢的现有技术和新兴技术，以及量子力学（密度泛函理论）计算。这些研究组成部分将通过定向晶体的红外光谱连接起来，这项技术已被证明是纳米材料研究的基础。我们的工作最初将集中在简单的氧化矿物，如金红石和辉石，这组相通常在NAMs研究中代表性不足，但其研究可以极大地有利于整个领域，并为技术材料的发展带来额外的好处。该奖项反映了美国国家科学基金会的法定使命，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。

Hydrogen exists as a minor component in numerous crystalline substances as molecular water and hydroxide ions, the so-called hydrous components. Minerals with these components include those that make up the Earth and synthetic industrial analogues that are of technological importance. The hydrogen in Earth’s minerals account for the vast majority of our planet’s hydrogen and has a profound effect on the behavior of Earth’s interior. Similarly, hydrous components can significantly modify the material properties of synthetic materials, such as semiconductors. Despite the clear importance of hydrogen in these contexts, there remain two fundamental uncertainties: 1) where does the hydrogen incorporate into crystal structures and 2) at what concentrations hydrogen is present. This work will address both issues through a comprehensive approach of both laboratory experiments and computer simulations. This will include development of analytical techniques for hydrogen detection, detailed spectroscopic studies, and interpretation of experimental data from quantum mechanics calculations. In addition to continuing work on previously studied silicate minerals (the most abundant minerals in the earth), the research will also focus on binary oxide minerals. Binary oxides are not only geologically relevant, but also have extreme relevance in many established and emerging technologies, ranging from solar cells, to lasers, touch screens, pigments, semiconductors, and flat screen displays. Hydrogen impurities have been shown to play a key role in these settings. Thus, this research will not only be important for understanding the inner workings of our planet, but will also be significant for the development of new technologies.It has long been understood that hydrous components (OH- and H2O) in nominally anhydrous minerals (NAMs) are of great importance in earth science. These phases, which include abundant mantle phases such as olivine, garnet, pyroxene and ringwoodite, are likely the largest reservoir for hydrogen in the Earth. The trace hydrogen in NAMs often has outsized effects on a wide range of their material properties, from melting points, to mechanical deformation, thermal and electrical conductivity, color, radiation stability. Despite the clear significance of hydrogen in NAMs, there persist two fundamental issues. First is the quantification of hydrogen concentrations in these phases. Numerous techniques have been attempted or utilized over the last few decades including nuclear profile analysis and SIMS measurements, but the technical challenges related to measuring trace hydrogen concentrations in NAMs have proven difficult to overcome. Second is the identification of specific hydrogen sites in NAMs. Although some defect sites have been identified in specific NAMs such as garnets, there is little recourse for establishing the detailed defect structures in most phases. Our proposed solution to these issues is a holistic approach that considers both established and emergent techniques for measuring trace hydrogen in minerals, and quantum mechanics (density functional theory) calculations. These research components will be linked through infrared spectroscopy of oriented crystals, a technique that has proven fundamental in the study of NAMs. Our work will initially focus on simple oxide minerals such as rutile and stishovite, a group of phases that has typically been underrepresented in research into NAMs, but whose study could greatly benefit the field as a whole, with additional benefits to the development of technological materials.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.