Samson Phases: Interplay of Theoretical Ideas and the Synthesis of New Phases

该项目解决了稳定钠镉（NaCd2）、铜镉（Cu4 Cd3）和铝镁（Al3 Mg2）体系中一系列复杂（1000个原子/单元电池）金属间相的因素。初步的量子力学计算表明，它们不同寻常的复杂性是由于将缺陷面插入到一个简单的晶体结构中，将其分解成纳米级的碎片。由于这些碎片之间的边界是周期性排列的，因此可以用x射线晶体学进行研究。这为观察影响材料性能的晶界现象提供了难得的机会。理论计算将用于检查这些边界如何赋予参孙结构的稳定性。该项目还将针对展示这些边界的新阶段的合成，并重新评估Samson的原始结构，这些结构有未被发现的超级结构的暗示。金属间化合物领域是专门的，很大程度上是由于相的剪切数量，没有理论来联系它们。该项目旨在用同样的语言发展这种联系理论，使学生能够理解有机化学和无机化学，即分子轨道理论。该项目支持PI作为NSF MPS杰出博士后与瑞典斯德哥尔摩大学Sven Lidin教授研究小组之间的合作。它旨在揭示稳定金属元素之间形成的固态化合物的因素。它将解释为什么一些金属元素的比例会导致简单的合金结构（2到4个原子/单位电池），而另一些则会导致斯坦·萨姆森在20世纪60年代发现的极其复杂的结构（1000个原子/单位电池）。初步的量子力学计算表明，这些复杂的结构是由于在一个简单的晶体结构中插入了缺陷面。不像典型的材料缺陷是随机出现的，在Samson相中，缺陷形成规则的图案。这种规律性允许使用x射线晶体学在原子对原子的分辨率上观察缺陷，提供了对材料特性如此重要的缺陷现象的罕见一瞥。理论计算将检验这些缺陷面如何赋予参孙结构稳定性。实验工作的目标是合成具有这些结构特征的新化合物，并重新评估Samson的原始化合物，这些化合物可能比当时的技术所能看到的更复杂。金属元素间化合物的研究领域是专门的，这主要是由于存在的化合物数量有限，而没有理论将它们联系起来。这个项目的目的是在分子轨道理论的语言中发展这种联系理论，使学生能够理解有机化学和无机化学。

This project addresses the factors stabilizing a series of complex (1000 atom/unit cell) intermetallic phases in the sodium-cadmium (NaCd2 ), copper-cadmium (Cu4 Cd3 ), and aluminum-magnesium (Al3 Mg2 ) systems. Preliminary quantum mechanical calculations suggest their unusual complexity results from the insertion of defect planes into a simple crystal structure breaking it up into nanometer-scale fragments. As the boundaries between these fragments are periodically arrayed, they are amenable to study by X-ray crystallography. This provides a rare glimpse at grain boundary phenomena that influence material properties. Theoretical calculations will be used to examine how these boundaries confer stability to Samson's structures. This project will also target the synthesis of new phases exhibiting these boundaries, and reevaluate Samson's original structures which have hints of undetected super-structuring. The field of intermetallics is specialized due largely to the shear number of phases with no theory to interrelate them. This project aims to develop this connective theory within the same language that makes organic and inorganic chemistry accessible for students, namely molecular orbital theory.%%%This project supports a collaboration between the PI, as an NSF MPS Distinguished Postdoctoral Fellow, and the research group of Professor Sven Lidin at Stockholm University, Sweden. It is aimed at uncovering the factors stabilizing solid-state compounds formed between metallic elements. It will address why some ratios of metallic elements lead to simple alloy structures (with two to four atoms/unit cell) while others give the extremely complex structures discovered by Sten Samson in the 1960s (1000 atom/unit cell). Preliminary quantum mechanical calculations suggest these complex structures result from the insertion of defect planes into a simple crystal structure. Unlike typical material defects, in which the defects occur randomly, in Samson's phases the defects make regular patterns. This regularity allows the defects to be seen at atom-by-atom resolution with the use of X-ray crystallography, providing a rare glimpse at the defect phenomena so important to material properties. Theoretical calculations will examine how these defect planes confer stability to Samson's structures. Experimental work will target the synthesis of new compounds exhibiting these structural features, and the reevaluation of Samson's original compounds, which are probably even more complicated than could be seen with the technology of the time. The field of compounds between metallic elements is specialized, largely due to the shear number of compounds existing with no theory to interrelate them. This project aims to develop this connective theory within the language that makes organic and inorganic chemistry accessible for students - that of molecular orbital theory.