Novel Intermetallic Chemistry: Approximants, Quasicrystals, and Rare-Earth-Metal-Rich Systems

技术摘要本研究的主要目标是在富金属系统的未知区域发现和表征某些全新类型的化合物，并开发和理解它们的结构、键合和性质。 开拓性的探索将继续定义非周期准晶及其晶体近似物的新例子，具有特别低价电子浓度的金属间化合物系统，表现出不寻常的晶体结构和特殊的电子稳定性。活性金属（Ca、Ba等）? Pt，Au，Ag？Triel、Tetrel（13、14族）元素是典型的三元组元。新的化学见解，其组成，结构，键合和特殊的电子稳定性将被利用。还寻求表现出不同种类的特殊电子效应的新的富含金属的组合物，例如，电子赝隙合成探索与物理表征一起也将研究新的视野和意想不到的化学内的稀土和过渡金属与主族准金属或非金属阴离子配对的富金属阳离子网络，特别是Te，Sb或Bi。 这些阶段在本质上是相反的凝聚的金属间化合物？盐？含有第一部分中描述的聚阴离子网络和简单阳离子。周期表中的大多数元素都是金属，因此两种或多种金属元素之间形成的化合物占可能化合物的很大一部分，所有其他因素都被忽略。此外，人们对大多数富金属材料知之甚少，这些材料相对于表中其他更常规元素制成的化合物，其性质和结构通常是独特的。 我们正在寻求扩展和推进固态和材料化学的概念和知识到金属间化学的未开发区域，特别是那些相对贫穷的电子周围的一些特殊化学和物理的经典例子。准晶和它们的近似物就是这种特殊的和同时代的相的例子。从更广泛的角度来看，多年来，我们的研究计划扩大和加强了世界各地固态和材料化学前沿的教育和研究计划。在那些已经完成博士学位的人中，在这些实验室从事博士后研究的人员中，有30人在国内担任学术或国家实验室职务，24人在国外担任职务，这些群体占总参与者的50%。

TECHNICAL ABSTRACTThe principal goals of this research are to discover and characterize certain totally new types of compounds in unknown regions of metal-rich systems and to develop and understand their structures, bonding and properties. Pioneering explorations will continue to define new examples of aperiodic quasicrystals and their crystalline approximants, intermetallic systems with particularly low valence electron concentrations that exhibit unusual crystal structures and special electronic stabilities. The active metal (Ca, Ba, etc.) ? Pt, Au, Ag ? triel, tetrel (group 13,14) elements are typical ternary components. New chemical insights into their compositions, structures, bonding and special electronic stabilities will be exploited. New metal-rich compositions that exhibit different kinds of special electronic effects are also sought, e.g., electronic pseudogaps. Synthetic explorations together with physical characterizations will also examine new horizons and unexpected chemistry within metal-rich cationic networks of rare-earth and transition metals paired with main-group metalloid or nonmetal anions, of Te, Sb, or Bi especially. These phases are in essence the inverse of the condensed intermetallic ?salts? containing polyanionic networks and simple cations described in the first part. NON-TECHNICAL ABSTRACT The majority of elements in the Periodic Table are metals, and thus compounds formed between two or more metallic elements make up a large fraction of possible compounds, all other factors being neglected. Moreover, very little is known about most metal-rich materials, which are generally unique in their properties and structures relative to compounds made of other more conventional elements in the Table. We are seeking to extend and advance solid state and materials chemistry concepts and knowledge into unexplored regions of intermetallic chemistry, particularly those relatively poor in electrons around a few classical examples of special chemistry and physics. Quasicrystals and their approximants are examples of such special and contemporary phases. In a broader view, educational and research programs at the frontiers of solid state and materials chemistry around the world have over the years been broadened and strengthened by our research programs. Among those who have completed Ph.D. or postdoctoral research in these labs, 30 hold academic or National Laboratory positions in this country, and 24 do so overseas, these groups constituting of 50% of the total participants.