砷化锑：化合物SbAs中的化学排序
Antimony arsenide: Chemical ordering in the compound SbAs
摘要：
半金属V族元素由于小的间接能带重叠而显示出丰富的相关电子现象，这导致在具有高迁移率的费米能量下相对小但相等的空穴和电子的数量。它们的电子键合特性产生了一种独特的晶体结构，即菱形A7结构，它在每个位置上容纳孤对电子。在这里，我们表明，A7结构可以显示Sb和As的化学顺序，这是以前认为随机混合。我们的化合物SbAs的结构表征进行单晶和高分辨率同步辐射X射线衍射，中子和X射线对分布函数分析。所有的最小二乘精化指示Sb和As的排序，导致在没有反转对称性的GeTe型结构。高温衍射研究揭示了在550 K附近的有序转变。传输和红外反射率测量以及第一性原理计算证实了SbAs是一种半金属，尽管其直接带间距大于Sb或As。由于半金属中即使是微小的取代，特别是Bi_{1-x} Sb_x，也可以打开半导体能隙，因此有必要进一步研究A7晶格上化学有序和电子结构之间的相互作用。
英文摘要：
The semimetallic Group V elements display a wealth of correlated electron phenomena due to a small indirect band overlap that leads to relatively small, but equal, numbers of holes and electrons at the Fermi energy with high mobility. Their electronic bonding characteristics produce a unique crystal structure, the rhombohedral A7 structure, which accommodates lone pairs on each site. Here we show that the A7 structure can display chemical ordering of Sb and As, which were previously thought to mix randomly. Our structural characterization of the compound SbAs is performed by single-crystal and high-resolution synchrotron x-ray diffraction, and neutron and x-ray pair distribution function analysis. All least-squares refinements indicate ordering of Sb and As, resulting in a GeTe-type structure without inversion symmetry. High-temperature diffraction studies reveal an ordering transition around 550 K. Transport and infrared reflectivity measurements, along with first-principles calculations, confirm that SbAs is a semimetal, albeit with a direct band separation larger than that of Sb or As. Because even subtle substitutions in the semimetals, notably Bi_{1-x}Sb_x, can open semiconducting energy gaps, a further investigation of the interplay between chemical ordering and electronic structure on the A7 lattice is warranted.
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