Lattice Properties of Crystalline Solids with Glasslike Properties: Ultrasound Studies of Inclusion Compounds and Quasicrystals

这一建议旨在研究各种“玻璃状晶体”(同时反映结晶和玻璃性质的材料)的弹性响应和超声波衰减。将解决的科学问题包括：(A)包裹体化合物、准晶和结构玻璃之间的关系，(B)包裹体化合物和/或准晶固有的隧穿状态(通常存在于玻璃中)，以及(C)结构-性质关系--各种结构特征可以在多大程度上用于预测特定材料的弹性性质？这项研究项目将使用共振超声频谱(RUS)来探测被调查材料的弹性性质。RUS是一种基于测量自由振动体的共振来确定固体弹性模数的新技术。材料的超声波衰减将使用标准的脉冲回波技术进行测量。这项提议将有助于密西西比大学一个强大的固态项目的发展。无论是高级本科生还是研究生，都将在超声波实验和低温物理技术方面获得深入的经验。“普通”材料要么是晶体(具有长程有序，即原子按周期排列)，要么是玻璃(没有长程有序)。这项提议将研究一些“特殊”材料的性质，如包裹体化合物和准晶。这些材料同时显示出结晶和类似玻璃的特性。该项目将使用一种相对较新的技术--共振超声光谱(RUS)，重点研究这些非凡固体的弹性性质。一项对显示玻璃状和水晶特征的不同寻常组合的材料的研究预计将在两个方面产生影响。首先，对这些材料中发现的玻璃性质的调查有望更好地理解玻璃行为的起源。由于这些材料对技术(热电)应用很感兴趣，因此更好地了解它们的性能对于设计具有优异性能的材料至关重要。其次，这项研究将有助于培养密西西比州本科生和研究生水平的年轻科学家，他们将获得凝聚态物理领域的深入经验。

This proposal is designed to investigate the elastic response and ultrasonic attenuation of a wide variety of "glasslike crystals" (materials that simultaneously reflect both crystalline and glasslike properties). The scientific issues that will be addressed include: (a) the relationship between inclusion compounds, quasicrystals, and structural glasses, (b) are tunneling states (which are typically found in glasses at low temperatures) intrinsic to inclusion compounds and/or quasicrystals, and (c) structure-property relationships - to what extent can various structural features be used to predict the elastic properties of a given material? This research project will use Resonant Ultrasound Spectroscopy (RUS) to probe the elastic properties of the materials under investigation. RUS is a novel technique for determining the elastic moduli of solids, based on the measurement of the resonances of a freely vibrating body. The ultrasonic attenuation of the materials will be measured using a standard pulse-echo technique. This proposal will contribute toward the development of a strong solid-state program at The University of Mississippi. Both advanced undergraduate and graduate students will gain in-depth experience in ultrasound experiments and the techniques of low temperature physics."Ordinary" materials are either crystals (with long-range order, i.e., the atoms are arranged in a periodic array) or glasses (with no long-range order). This proposal will investigate the properties of some "extraordinary" materials such as inclusion compounds and quasicrystals. These are materials that simultaneously display both crystalline and glasslike properties. The project will focus on the elastic properties of these remarkable solids, using a relatively new technique, Resonant Ultrasound Spectroscopy (RUS). A study of materials that display the unusual combination of glasslike and crystalline features is expected to have an impact on two fronts. First, the investigation of the glasslike properties found in these materials is expected to lead to a better understaanding of the origin of glassy behavior. Since these materials are of interest for technological (thermoelectric) applications, a better understanding of their properties is essential for the design of materials with superior properties. Secondly, this research will contribute to the training of young scientists at the undergraduate and graduate level in Mississippi, who will gain in-depth experience in the field of condensed-matter physics.