New Intermetallic Phases with Matter Occupancy Waves

该项目将专注于新的金属间化合物的发现、结构确定和性能测量，有效地结合定量计算方法和定性理论来开发实验性的生产性结构和成键模型。重点放在金属间化合物系统上，在这些系统中，尚不清楚主族元素-金属、金属-金属或元素-元素键是主导结构和性能的。之所以选择这类材料，是因为它们难以理解，而且这些材料具有不寻常的成键趋势平衡，这很可能导致材料具有新的性质，如物质占据波和亚晶格剪切图案。综合努力的一个焦点是下部结构-上层建筑关系。晶体超结构为成键提供了内在的线索。如果一类材料出现了一系列的超结构，这通常是一个线索，表明这些结构处于决定物理力的某种谨慎(而且很容易被干扰)的平衡中。将研究过渡金属-主族相互作用主导结构的相(Nowotny烟囱梯形相)，包括电负性和电正性原子的金属合金(铜-锌)，以及组成元素之间能隙减小的方网体系(三元稀土和各种三元化合物，其中过渡金属和主族元素在晶格中交替出现)。这些系统不仅仅是迫使人们超越Zintl的概念，它们还具有共同的结构特征。所有这些系统都表现出物质占据波超结构，这是一种通常不能用传统的电荷密度波参数来处理的有序类型。这也与晶体生长、离子传导性以及可能出现的亚晶格相互移动或剪切的新现象有关。将发展新的理论方法来看待这种上层建筑。目标是将实验工作和理论工作充分结合起来。[这项研究支持的研究生可以合理地预期在他们的论文中有合成、性质表征和理论计算的元素。]这些新材料的结构、组成、性质相关性可能表现出有趣的磁性、超导和离子导电行为。学生将接受固态合成、性质表征、理论计算和建模方面的培训，所有这些都是与当前学术和工业就业机会高度相关的领域。

This project will focus on new intermetallic compound discovery, structure determination and property measurement, effectively coupled with quantitative computational methods and qualitative theory to develop experimentally productive structural and bonding models. The focus is on intermetallic systems where it is not clear whether main group element-metal, metal-metal, or element- element bonding dominates structures and properties. This class of materials has been chosen because they are difficult to understand and because these materials possess an unusual balance of bonding trends that could very well lead to materials with novel properties such as matter occupation waves and sublattice shear patterns. A focus of the synthetic efforts is substructure-superstructure relations. Crystalline superstructures provide intrinsic clues as to the bonding. If a range of superstructures appears for a class of materials, that is often a clue that the structures are in some careful (and easily perturbed) balance of determining physical forces. Phases will be studied in which transition metal -main group interactions dominated the structure (Nowotny chimney ladder phases), metal alloys involving both electronegative and electropositive atoms (Copper-Zinc) and square net systems with reduced energy gaps between the composing elements (ternary rare earths and a variety of ternary compounds with alternating transition metal and main group elements in the lattice). These systems do more than just force one to go beyond the Zintl concept, they also bear structural features in common. All these systems exhibit matter occupation wave superstructures, a type of ordering which can not in general be treated by the traditional charge density wave arguments. There are also connections to problems of crystal growth, of ionic conductivity and a possible new phenomenon of sublattices moving or shearing through each other. New theoretical ways at looking at such superstructures will be developed. The goal is to full couple experimental and theoretical work. [The graduate students supported by this research may be reasonably expected to have elements of synthesis, property characterization and theoretical computation in their theses.]%%%Structure, composition, property correlations of these new classes of materials may exhibit interesting magnetic, superconductivity, and ionic conducting behavior. Students will be trained in solid state synthesis, property characterization and theoretical computation and modeling, all of which are areas of high relevance to current academic and industrial job opportunities.