Development of New Diamond Cell Technology for Ultrahigh-Pressure Single-Crystal Structure Analysis Using X-ray Diffraction

0217389毛，德拉，普雷维特近年来，人们对超高压研究成果的兴趣与日俱增，主要是因为在实验室中模拟具有深部地质环境特征的条件的独特可能性。达到约25 Gpa以上静压力的主要工具是钻石顶压室(DAC)。除了等温压缩研究外，DAC还可以用于从室温到几百万巴的现场实验，温度从接近0K到几千度。在10 Gpa以上的压力下，大多数结构分析仅限于多晶样品，因为在较高压力下进行单晶衍射研究的技术并不发达。该项目将把单晶结构分析的压力能力从10 Gpa扩展到120 Gpa，甚至更高的压力。这一压力区异常丰富，极大地改变了材料的电、磁、热、弹性和成键特性。准确确定伴随这些变化的原子位置和电子分布是理解这些过程的关键。我们计划开发的实验和计算技术将使实验室和同步加速器X射线源的超高压晶体结构研究成为可能。随着样品垫片、压力介质、钻石砧座、背板和钻石电池设计的新发展，我们将能够将(10？m)3无应变单晶样品带到上述压力下。基于这些发展的实验将为地球、行星和材料科学中长期寻求的重要科学问题提供明确的答案，包括作为行星深部主要组成部分的硅酸盐、氧化物、冰和凝析气体的根本变化。

0217389Mao, Dera, PrewittIn recent years, increasing interest in ultrahigh-pressure research results primarily from the unique possibility to simulate in the laboratory the conditions that are characteristic of deep geological environments. The primary tool for achieving static pressures above about 25 GPa is the diamond anvil cell (DAC). Apart from isothermal compression studies, the DAC can also be used for in-situ experiments from room pressure to several megabars at temperatures from close to 0 K to several thousands of degrees. Most structure analysis at pressures above about 10 GPa has been limited to polycrystalline samples because the technology for single-crystal diffraction studies at higher pressures is not well-developed. This project will extend the pressure capability of single-crystal structure analysis from 10 to 120 GPa and even higher pressures. This pressure region is extraordinarily rich in phenomena that dramatically change electronic, magnetic, thermal, elastic, and bonding properties of materials. Precise determination of atomic positions and electron distributions accompanying these changes is the key for understanding the processes. The experimental and computational techniques we are planning to develop will make possible ultrahigh-pressure crystal-structure studies with both laboratory-based and synchrotron x-ray sources. With new developments in sample gaskets, pressure media, diamond anvils, backing plates, and diamond cell design, we will be able to bring a (10 ?m)3 sample of an unstrained single crystal to the pressures stated above. Experiments based on these developments will provide definitive long-sought answers to important scientific questions in Earth, planetary, and materials sciences, including the fundamental changes of silicates, oxides, ices, and condensed gases that are the main components of deep planetary interiors.