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A Tour of Soft Atomic Motions: Chemical Pressure Quadrupoles Across Transition Metal–Main Group 1:2 Structure Types
Chemistry of Materials ( IF 8.6 ) Pub Date : 2022-11-10 , DOI: 10.1021/acs.chemmater.2c02410
Kendall R. Kamp, Daniel C. Fredrickson

The rational design of materials requires an understanding of the relationships between structure and properties. In some fields, advances in computational tools and modeling have mapped out many of these connections. In the realm of intermetallics, however, principles for such relationships are still needed. Recently, we illustrated how the DFT–Chemical Pressure (CP) analysis can link geometrical motifs within crystalline arrangements to the phonon band structures of intermetallics and thus the physical properties related to vibrations and atomic motion. The key indicators here are quadrupolar CP features─distributions in which positive and negative interatomic pressures are oriented perpendicular to one another. These quadrupoles then create low energy paths of motion for the atoms that can be linked to various structural phenomena, such as anisotropic vibrations and incommensurate modulations. In this article, we survey the presence of CP quadrupoles in a collection of TE2 structures (T = transition metal and E = main group element) and the roles they play in the behavior observed for these compounds. We begin by developing a metric for CP quadrupolar character, which can be calculated from the output of CP analysis. After compiling these metrics for 17 TE2 structure types, we delve deeper into four systems detected as exhibiting atomic sites with quadrupolar character: (1) the Co–Sn binary system, where the quadrupoles on the Co atoms in CuAl2-type CoSn2 direct the features of its superstructure in CoSn3; (2) arsenopyrite-type CoSb2, in which the highly quadrupolar CP distributions on the Sb atoms correlate with the motions followed during the phase transition to its high-temperature marcasite-type form; (3) the CrSi2 structure, in which the expansion of the lattice is predicted to open a helical path of potential soft motion analogous to that underlying the Nowotny Chimney Ladder series; and (4) the CdAs2 type, whose CP features anticipate the ability to incorporate Li atoms as guests. Together, these case studies highlight the potential for CP quadrupoles to link local atomic arrangements with a variety of emergent properties in intermetallic phases.

中文翻译:

软原子运动之旅:跨过渡金属的化学压力四极 - 主族 1:2 结构类型

材料的合理设计需要了解结构和性能之间的关系。在某些领域,计算工具和建模的进步已经描绘出其中的许多联系。然而,在金属间化合物领域,仍然需要这种关系的原则。最近,我们说明了 DFT-化学压力 (CP) 分析如何将晶体排列中的几何图案与金属间化合物的声子带结构联系起来,从而与振动和原子运动相关的物理特性联系起来。这里的关键指标是四极 CP 特征——正负原子间压力相互垂直的分布。然后这些四极子为原子创造低能量运动路径,这些路径可以与各种结构现象联系起来,例如各向异性振动和不相称的调制。在这篇文章中,我们调查了 TE 集合中 CP 四极杆的存在2种结构(T = 过渡金属,E = 主族元素)以及它们在观察到的这些化合物的行为中所起的作用。我们首先开发 CP 四极特性的度量标准,它可以从 CP 分析的输出中计算出来。在为 17 种 TE 2结构类型编制了这些指标后,我们深入研究了四个被检测为具有四极特征的原子位点的系统:(1) Co-Sn 二元系统,其中 CuAl 2型 CoSn 2中 Co 原子上的四极在CoSn 3中指导其超结构的特征;(2)毒砂型CoSb 2,其中 Sb 原子上的高度四极 CP 分布与相变到其高温白铁矿型形式期间所遵循的运动相关;(3) CrSi 2结构,其中晶格的膨胀预计会打开潜在软运动的螺旋路径,类似于 Nowotny Chimney Ladder 系列下的路径;(4) CdAs 2类型,其CP特征预期能够结合Li原子作为客体。总之,这些案例研究突出了 CP 四极杆将局部原子排列与金属间相中的各种涌现特性联系起来的潜力。
更新日期:2022-11-10
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