Simple Molecular Solids at Ultrahigh Pressure

本研究涉及压力诱导转化的实验研究和简单分子体系在宽温度范围内超过300 GPa（3兆巴）的超高静压力下的新行为。实验将集中在由低z双原子和三原子系统、稀有气体和含有这些物种的致密化合物和合金形成的代表性固体的转变上。该项目利用了钻石砧细胞技术的最新发展，以及基于第一性原理计算的各种理论预测。新的同步加速器x射线和中子衍射技术将用于晶体结构的测定，包括氧和氢同位素的低温相。最近开发的高压x射线非弹性散射技术将用于测量压力效应，并了解电子激发的密度依赖性，它们的带宽和色散。输运方法将用于研究超导性和各种材料（包括富氧和富氢固体）向新状态的可能转变。将有系统地努力扩大对高压社区很重要的静态高压技术的压力范围、准确性和灵敏度，包括在国家用户设施中使用的技术。包括化学、材料科学和行星科学在内的许多其他领域也将受益。该项目的一个主要目标是培养物理学和材料科学方面的青年科学家。一名研究生和一名博士后将直接得到这项资助。本科生和优秀高中生也会参加。所有人都为未来在学术界、国家实验室和高科技行业的职位做好了准备。超高压对简单分子的影响是物理和化学中的一个经典问题。在现在可以在实验室中达到的非常高的压力下，氢、氮、氧、水和相关物质等分子转变成新的材料，包括致密金属、独特的超导体和不寻常的化合物。其中许多是理论上没有预料到的，它们的发现极大地增强了对整个物质的理解。在这个项目中，简单分子在超高静态压缩到300 GPa（3兆巴）以上的情况下，在宽温度范围内的新行为的新实验将使用一种被称为金刚石砧细胞的强大设备进行。该项目利用了最近的技术发展，将钻石砧细胞与敏感的分析方法结合起来，并对这些材料进行了新的理论预测。大部分实验将在同步辐射和中子源等主要国家设施进行，在那里将开发新技术并培训科学家。各种各样的激光技术以及高灵敏度的电学和磁学方法将被使用，例如，从压缩分子材料中研究超导性。将有系统的努力扩大高压技术的压力范围、准确性和灵敏度，这对高压社区很重要，包括国家设施的重大项目。许多其他领域，包括化学、材料科学和行星科学都将从中受益。最后，该项目将培养一批青年科学家，包括研究生、博士后、本科生实习生，甚至是优秀的高中生。这项研究将为这些学生在学术界、国家实验室和高科技行业的职位做好准备。

This research concerns experimental studies of pressure-induced transformations and novel behavior of simple molecular systems to ultrahigh static pressures above 300 GPa (3 megabars) over a broad temperature range. The experiments will focus on transformations in representative solids formed from low-Z diatomic and triatomic systems, rare gases, and dense compounds and alloys containing these species. The project takes advantage of recent developments in diamond-anvil cell techniques, and a variety of theoretical predictions based on first-principles calculations. New synchrotron x-ray and neutron diffraction techniques will be used for crystal structure determination, including low temperature phases of oxygen and hydrogen isotopes. Recently developed high-pressure x-ray inelastic scattering techniques will be used to measure pressure effects and to understand the density dependence of electronic excitations, their bandwidths, and dispersion. Transport methods will be used to study superconductivity and possible transformations to novel states of in a range of materials, including oxygen and hydrogen-rich solids. There will be a systematic effort to extend the pressure range, accuracy, and sensitivity of static high-pressure techniques important for the high-pressure community, including those used at national user facilities. Numerous other fields, including chemistry, materials science, and planetary science should also benefit. A major goal of this project is the training of young scientists in physics and materials science. A graduate student and a post-doctoral fellow will be supported directly under this grant. Undergraduates and exceptional high-school students also participate. All are prepared for future positions in academia, national laboratories, and high-technology industries.The effect of ultrahigh pressures on simple molecules is a classic problem in physics and chemistry. Under the very high-pressures that can now be reached in the laboratory, molecules such as hydrogen, nitrogen, oxygen, water, and related substances transform to novel materials, including dense metals, unique superconductors, and unusual compounds. Many of these were unanticipated theoretically, and their discovery has greatly enhanced understanding of matter as a whole. In this project, new experiments on the novel behavior of simple molecules at ultrahigh static compressed to above 300 GPa (3 megabars) over a broad temperature range will be carried out using a powerful device known as the diamond anvil cell. The project takes advantage of recent developments in techniques that couple the diamond-anvil cell with sensitive analytical methods, and new theoretical predictions for these materials. A large portion of the experiments will take place at major national facilities such as synchrotron radiation and neutron sources, where new techniques will be developed and scientists trained. A variety of laser techniques as well as highly sensitive electrical and magnetic methods will be used, for example to study superconductivity from greatly compressing molecular materials. There will be a systematic effort to extend the pressure range, accuracy, and sensitivity of high-pressure techniques important for the high-pressure community, including major programs at national facilities. Numerous other fields, including chemistry, materials science, and planetary science should benefit. Finally, this project will train a number of young scientists, including graduate students and post-doctoral fellows as well as undergraduate interns and even exceptional high-school students. The research will prepare these students for positions in academia, national laboratories, and high-technology industries.