Simple Molecular Systems at Ultrahigh Pressure

*非技术摘要*本项目探索极端条件下材料的性质--压力达到或超过300万大气压(3兆巴)，温度从低温条件到数千度。在这些极端条件下，简单的液体和气体可以转化为新材料，包括不寻常的金属，甚至超导体。这项研究将研究这些和相关的高压转变的性质，并将在简单材料被压缩到非常高的密度时寻找全新的现象。因此，这项工作将扩大我们对凝聚态中基本相互作用的知识，并导致新材料的创造。这些实验将利用国家主要设施，如新的同步辐射和中子散射源。广泛的参与者将从这项工作中受益，包括高中生、本科生、研究生、博士后助理和访问调查人员。就其对基础科学、潜在的技术应用和科学家培训的重要性而言，这项工作处于一个快速增长的物理科学领域的前沿。*技术摘要*这一个人研究人员奖将支持使用最近开发的钻石顶压室、同步辐射X射线、中子散射、光谱学和传输探测器在广泛的温度范围内在高达300 Gpa(3兆巴)的压力下继续研究简单分子材料的行为。这些实验将集中在由低Z双原子系统、稀有气体以及含有这些物种的致密化合物和合金形成的典型固体中的转变。同步加速器x射线和中子衍射技术将用于鉴定氧、氮和氢的新型高压相的晶体结构，以及选定的多原子化合物和新发现的高压化合物。拉曼光谱、红外光谱和光学光谱将在更广泛的条件下探测这些系统中的成键、相变和电子性质，包括在氢的稠密导电流体相中进行测量。化学计量氢化合物、掺杂氢体系、选定的包合物和其他分子材料的高压行为也将被研究。高压x射线非弹性散射将被用来测量压力对动态结构因子和电子结构的影响，扩展了对压缩激子和带隙的直接测量。高灵敏度的磁化率和新的电阻率方法将被用来研究这些材料的超导电性，范围可达300 Gpa。这些研究中的每一项都将涉及对学生、博士后研究员和其他研究人员进行最先进的凝聚态技术的培训。

*** NON-TECHNICAL ABSTRACT ***This project explores the nature of materials at extreme conditions -- pressures up to and beyond 3 million atmospheres (3 megabars), and temperatures from cryogenic conditions to thousands of degrees. Under these extreme conditions, simple liquids and gases can be converted to novel materials, including unusual metals and even superconductors. This research will examine the nature of these and related high-pressure transformations and will search for altogether new phenomena when simple materials are compressed to very high densities. As such, the work will expand our knowledge of fundamental interactions in condensed matter as well as lead to the creation of new materials. The experiments will make use of major national facilities such as new synchrotron radiation and neutron scattering sources. A wide cross-section of participants will benefit from the work, including high school students, undergraduates, graduate students, postdoctoral associates, and visiting investigators. In terms of its importance to fundamental science, potential applications to technology, and the training of scientists, the work is at the forefront of a rapidly growing area of the physical sciences.*** TECHNICAL ABSTRACT *** This individual investigator award will support continued studies of the behavior of simple molecular materials at pressures up to above 300 GPa (3 megabars) over a broad range of temperatures using recently developed diamond-anvil cell, synchrotron x-ray, neutron scattering, optical spectroscopy, and transport probes. The experiments will focus on transformations in representative solids formed from low-Z diatomic systems, rare gases, and dense compounds and alloys containing these species. Synchrotron x-ray and neutron diffraction techniques will be used to identify crystal structures of novel high-pressure phases of oxygen, nitrogen, and hydrogen, as well as of selected polyatomics and newly discovered high-pressure compounds. Raman, infrared, and optical spectroscopy will probe bonding, phase transformations, and electronic properties in these systems over a broader range of conditions, including measurements in the dense conducting fluid phase of hydrogen. The high-pressure behavior of stoichiometic hydrogen compounds, doped hydrogen systems, selected clathrates, and other molecular materials will also be investigated. High-pressure x-ray inelastic scattering will be used to measure pressure effects on dynamic structure factors and electronic structure, extending direct measurements of excitons and band gaps on compression. Highly sensitive magnetic susceptibility and new resistivity methods will be used to study superconductivity in these materials to the 300-GPa range. Each of these studies will involve the training of students, post-doctoral fellows, and other researchers in state-of-the-art condensed matter techniques.