Local Atomic Structure of Nearly-periodic Solids

一些技术上重要的新材料的局部原子结构，主要是晶体氧化物，将通过包括原子对分布分析在内的非晶体衍射技术来确定。研究的材料包括超导铜酸盐、具有巨大磁阻的锰酸盐、用于汽车催化剂载体的CeO2/ZrO2混合物和金属玻璃。这些材料中的许多平均具有周期性晶体结构，但表现出明显的局部结构偏离完美的周期性，这对于确定其性质至关重要。实验将使用国家设施提供的脉冲中子和同步加速器x射线进行。结果将通过我们小组开发的计算机建模方法进行分析。为了便于对结果的理解，理论研究将与其他理论小组合作进行。材料的性能最终取决于原子结构。最近的研究表明，局部原子结构，即原子几个原子直径范围内的结构，可能不是材料的平均结构。在许多情况下，这种局部变化不会产生显著的后果，但在许多情况下，材料的性质严重依赖于局部结构，而不是平均结构。本项目的目的是利用非晶体散射技术确定这些材料的局部原子结构。三种材料系统将被检查，所有这些都是技术上的重要性。* * *

9628134 Egami The local atomic structure of some technologically important new materials, mostly crystalline oxides, will be determined by non-crystallographic diffraction techniques including the atomic pair-distribution analysis. The materials studied include superconducting cuprates, manganates with colossal magnetoresistance, CeO2/ZrO2 mixture for automotive catalyst support, and metallic glasses. Many of these materials have a periodic crystalline structure in average, but show significant local structural deviations from perfect periodicity that can be critically important in determining their properties. Experiments will be carried out using pulsed neutrons and synchrotron x-rays available at national facilities. Results will be analyzed by computer modeling methods developed in our group. To facilitate understanding of the results, theoretical studies will be carried out in collaboration with other theory groups. %%% The properties of a material ultimately depend on the atomic structure. Recent research has shown that the local atomic structure, that is, the structure within a few atomic diameters of an atom, may not be the average structure of the material. In many cases, such local variations do not have significant consequences, but in many cases the properties of a material are critically dependent on the local structure rather than the average structure. The purpose of this project is to determine the local atomic structure of these materials using non-crystallographic scattering techniques. Three materials systems will be examined, all of which are of technological importance. ***