Confronting Complexity in Intermetallics: A Synthetic, Structural and Theoretical Approach

技术解释 该项目涉及的合成，结构表征，性能和能带计算，是有晶格失配之间的两个金属结构图案（贵金属γ-黄铜超结构），大的立方相，可以分解成更简单的组件，同心二十面体对称集群组成的阶段，和结构组成的扩展缺电子集群。所有这些系统都位于金属-绝缘体边界附近，一些在一侧，一些在另一侧，具有复杂的缩放特性，并且可能包含其更多金属（共价）和更多离子组分之间的界面。他们测试了目前对纯金属、绝缘体或半导体有用的范例的边界。从事该项目的学生将学习如何应用现代电子结构计算来理解现在可以通过现代同步辐射衍射实验获得的复杂晶体结构。非技术解释文明的经典合金，黄铜和青铜，元素，铜银和金躺在拟议项目的核心。 我们今天对它们结构的理解仍然经常嵌入经典概念中：例如柏拉图多面体。该项目旨在对这些结构和其他衍生结构进行连贯的结构改造。 这将是从经典几何图像（例如，仍然用于理解伽马黄铜的结构）到基于简单量子力学计算的范例的重新加工。预计这种理解将演变成基于最小表面和互锁的相互交织的子结构的模型。选择正在研究的材料不仅是因为它们迄今为止被证明难以理解，而且还因为我们认为这些材料具有不寻常的键合趋势平衡，这很可能导致具有新特性的材料，例如离子和金属成分之间的分离，以及亚晶格剪切模式，影响这些基本合金的电和磁以及内聚特性的特性。

TECHNICAL EXPLANATION This project addresses the synthesis, structural characterization, properties, and band calculations for, are phases in which there are lattice mismatches between two metal structural motifs (noble metal gamma-brass superstructures), large cubic phases which can be decomposed into simpler components, phases composed of concentric icosahedral symmetry clusters, and structures composed of extended electron deficient clusters. All these systems lay near the metal-insulator boundary, some on one side, some on the other, have complex scaling properties, and potentially contain interfaces between their more metallic (covalent) and more ionic components. They test the boundaries of current paradigms useful for pure metals, insulators or semiconductors. Students working on this project will learn how to apply modern electronic structure calculations to understand the complex crystal structures that can now be obtained through modern synchrotron radiation diffraction experiments.NON-TECHNICAL EXPLANATIONThe classic alloys of civilization, brass and bronze, the elements, copper silver and gold lie at the heart of the proposed project. Our understanding today of their structures is remarkably still often imbedded in classical notions: the Platonic polyhedra for example. This project aims at a coherent structural reworking of these structures and the other structures derived from them. It will be a reworking from a classical geometrical picture (still used in understanding structures of gamma-brass for example), to paradigms based on simple quantum mechanical calculations. It is anticipated that the understanding will evolve into models based on minimal surfaces and interlocking intermeshed substructures. The materials being studied are chosen not just because they have hitherto proven difficult to understand but also because we think that such materials possess an unusual balance of bonding trends that could very well lead to materials with novel properties such as segregation between ionic and metallic components , and sub-lattice shear patterns, properties which affect the electrical and magnetic and cohesion properties of these essential alloys.