Studies of Defects, Disorder and Phase Transitions in Alloy Crystals via Diffuse Scattering

本计画旨在利用同步加速器X光与中子散射来阐明无序合金与缺陷晶体的详细结构。 它包含实验部分（无序合金中原子相关性和位移的测量）和理论部分（这些量与潜在电子结构的关系）。 新的合金将被研究，如零矩阵 Ni0.52Pt0.48，其平均散射为零，因为62Ni具有负的中子散射长度，而Cu62Ni，其中磁效应变得非常有趣，特别是源于自旋的位移。 扩展费米表面的散射痕迹和它们的起源在合金理论也将探讨。 最后，解释的两个长度标度现象是V2H，其中表面缺陷诱导连续相变，而体显示一级transition，将完成。在这个项目中，各种散射方法被应用于阐明一些有趣的和重要的结构在金属和合金的基本物理（电子）的起源。 这些散射技术利用了最先进的国家实验室，如先进的光子源在阿贡国家实验室，国家同步加速器光源在布鲁克海文国家实验室，新的NSF支持的中子仪器在国家标准与技术研究所，研究反应堆司，和高通量同位素反应堆在橡树岭国家实验室。 与马克斯·普朗克金属研究所（斯图加特）的合作正在顺利进行，并取得了丰硕成果。 基本目标是在原子水平上理解简单和复杂的合金，以便将它们的结构与功能联系起来。

This project is addressed to use synchrotron X-ray and neutron scattering to elucidate the detailed structure of disordered alloys and defective crystals. It contains both an experimental component (the measurement of atomic correlations and displacements in disordered alloys) and a theoretical component (the relation of these quantities to the underlying electronic structure). Novel alloys will be studied such as the null matrix Nio.52Pto.48 whose average scattering is zero as the 62Ni has a negative neutron scattering length and Cu62Ni where magnetic effects become very interesting, especially the displacements originating in the spins. Extended Fermi surface traces in the scattering and their origin in alloy theory will also be explored. Finally, the explanation of the two-length scale phenomenon is V2H, where surface defects induce a continuous phase transition while the bulk shows a first-order transition, will be completed.In this project a variety of scattering methods are applied to elucidate the underlying physical (electronic) origin of a number of interesting and important structures in metals and alloys. These scattering techniques take advantage of the most sophisticated national laboratories such as the Advanced Photon Source at the Argonne National Laboratory, the National Synchrotron Light Source at the Brookhaven National Laboratory, new NSF-supported neutron instrumentation at the National Institute for Standards and Technology, Research Reactor Division, and the High Flux Isotope Reactor at the Oak Ridge National Laboratory. Collaboration with the Max Planck Institute for Metals Research (Stuttgart) is well underway and has been quite productive. The basic aim is the understanding of both simple and complex alloys at the atomic level in order to relate their structure to their function.