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

0217389 Mao，Dera，Prewitt近年来，人们对超高压研究的兴趣日益增加，主要是因为在实验室中模拟深部地质环境特征条件的独特可能性。用于实现高于约25GPa的静压的主要工具是金刚石砧座单元（DAC）。除了等温压缩研究外，DAC还可用于从室温到几兆巴的原位实验，温度从接近0 K到几千度。大多数在10 GPa以上压力下的结构分析仅限于多晶样品，因为在更高压力下进行单晶衍射研究的技术还没有得到很好的发展。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。这个压力区域非常丰富的现象，显着改变材料的电子，磁性，热，弹性和键合特性。精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利用实验室和同步加速器X射线源进行超高压晶体结构研究成为可能。随着样品垫片、压力介质、金刚石砧、垫板和金刚石单元设计的新发展，我们将能够为客户带来（10？m）3个未应变的单晶的样品到上述压力。 基于这些发展的实验将为地球、行星和材料科学中的重要科学问题提供长期寻求的明确答案，包括硅酸盐、氧化物、冰和冷凝气体的基本变化，这些都是行星内部深处的主要成分。

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.