Dynamical Localization in High Temperature Crystals as Measured by Inelastic Neutron Scattering

通过非弹性中子散射测量高温晶体的动力学局域化

• 批准号: 0906491
• 负责人: Albert Sievers
• 金额: $ 40万
• 依托单位: Cornell University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2009
• 资助国家: 美国
• 起止时间: 2009-11-01 至 2014-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0906491&HistoricalAwards=false
• 关键词: Dynamical; Localization; Temperature; Crystals; Measured

****NON-TECHNICAL ABSTRACT****An important scientific idea is that of energy or the equivalence of heat and work; a concept central to the industrial revolution. At present solar radiation can be converted to many forms of energy by means of technology; but, to make energy produced this way an economical contribution to our national energy supply requires understanding the long-term stability of materials, especially those at high temperatures. Preliminary neutron scattering experiments on a crystal of salt at high temperatures by the Cornell-Lawrence Livermore National Laboratory collaboration have identified unexpected energy localization or hot spots in the crystal. These findings indicate a high temperature complexity for such a simple ionic lattice and point to the need for new understanding about the way energy is distributed and transported amongst atoms in real materials. This individual investigator program will make use of sophisticated measurement tools located at a variety of national facilities to examine and characterize in a systematic manner the hot spot behavior in high temperature crystals. The knowledge about such intrinsic material defects may be expected to ultimately impact the science of high temperature materials. Both graduate and undergraduate students will develop expertise in research methods and a variety of experimental techniques appropriate to this new interdisciplinary field.****TECHNICAL ABSTRACT****A long standing question in condensed-matter sciences and nonlinear dynamics is whether or not intrinsic localized vibrational modes (ILMs), which rely on nonlinearity and lattice discreteness and which have been explored in detail in macroscopic 1-D lattices, can appear in a 3-D atomic lattice in thermal equilibrium. Preliminary experiments using inelastic neutron scattering from crystalline solids by the Cornell-Lawrence Livermore National Laboratory collaboration have identified dynamical localization with well-defined discrete energies as a new, necessary component of high temperature lattice dynamics. Since high temperature materials now appear to be a natural habitat for dynamical localization and since such excitations are localized hot spots in the material they represent intrinsic material defects that may be expected to influence high temperature diffusion and ultimately the strength of materials. This individual investigator award supports a project to measure, with inelastic neutron scattering, the vibrational localization that appears in crystals at high temperatures. A goal of the project is to understand the properties and ramifications of ILMs in a variety of high temperature crystals. The experimental program will involve a postdoc, a graduate and undergraduate students, and will employ a suite of scattering measurement techniques located at national facilities, ranging from spallation source neutron scattering to reactor source thermal neutron scattering, to expand the knowledge about such excitations in dielectric crystals.

****非技术摘要****一个重要的科学思想是能量或热功等效；这是工业革命的核心概念。目前，通过技术手段，太阳辐射可以转化为多种形式的能量；但是，要使这种方式产生的能源对我们国家的能源供应做出经济贡献，需要了解材料的长期稳定性，特别是那些在高温下的材料。康奈尔-劳伦斯利弗莫尔国家实验室在高温下对盐晶体进行了初步的中子散射实验，发现了晶体中意想不到的能量局部化或热点。这些发现表明，这样一个简单的离子晶格具有高温复杂性，并指出需要对真实材料中能量在原子之间分布和传输的方式有新的认识。这个单独的研究者计划将利用位于各种国家设施的复杂测量工具，以系统的方式检查和表征高温晶体中的热点行为。有关这些材料固有缺陷的知识有望最终影响高温材料科学。研究生和本科生都将在研究方法和各种适合这个新的跨学科领域的实验技术方面发展专业知识。****技术摘要****在凝聚态科学和非线性动力学中，一个长期存在的问题是，依赖于非线性和晶格离散性的内在局域振动模式（ilm）是否可以出现在热平衡状态下的三维原子晶格中，这些模式已经在宏观一维晶格中进行了详细的探索。康奈尔-劳伦斯利弗莫尔国家实验室合作进行的结晶固体非弹性中子散射的初步实验已经确定了具有明确定义的离散能量的动力学局部化，作为高温晶格动力学的一个新的必要组成部分。由于高温材料现在似乎是动态局部化的自然栖息地，并且由于这种激励是材料中的局部热点，它们代表了可能影响高温扩散并最终影响材料强度的固有材料缺陷。这项个人研究者奖支持了一个项目，该项目利用非弹性中子散射来测量高温下晶体中的振动局域化。该项目的目标是了解各种高温晶体中ilm的性质和分支。该实验项目将涉及一名博士后、一名研究生和一名本科生，并将采用一套位于国家设施的散射测量技术，从散裂源中子散射到反应堆源热中子散射，以扩大对介电晶体中这种激发的认识。