Uncorrelated Bi off-centering and the insulator-to-metal transition in ruthenium A2Ru2O7 pyrochlores
Uncorrelated Bi off-centering and the insulator-to-metal transition in ruthenium A2Ru2O7 pyrochlores
复制标题
钌 A2Ru2O7 烧绿石中不相关的 Bi 偏心和绝缘体到金属的转变
DOI：
10.1103/physrevmaterials.3.095003
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发表时间：
2019
影响因子：
3.4
通讯作者：
Seshadri, Ram
中科院分区：
文献类型：
--
作者：
Laurita, Geneva;Puggioni, Danilo;Hickox-Young, Daniel;Rondinelli, James M.;Gaultois, Michael W.;Page, Katharine;Lamontagne, Leo K.;Seshadri, Ram
从基本物理学的角度来看，绝缘体到金属转变的研究是有趣的，并且处于这种转变边缘的材料具有有用的功能。通过成分调整来推动这种转变可以帮助设计有用的材料特性。在这里，我们研究了在固溶体氧化物烧绿石（。先前的工作已经建立了网站的障碍，从他们的理想晶体位置的Bi端元烧绿石作为孤对电子的立体化学活性的结果，thecations移动不连贯。然而，很少有人知道这种偏心固溶体的后果和它的作用，在确定电子基态。在这里，我们证明，通过总散射研究，即使是一个小的取代铋的pyroxidreAsite导致网站的混乱，提高了平均有效尺寸的theA-网站阳离子。这间接地增加了Ru-O-Ru共价性，这似乎在固溶体中从绝缘行为到金属行为的交叉中起着至关重要的作用。此外，密度泛函电子结构计算表明，孤对驱动的非相干阳离子位移的初级和次级（由于尺寸）电子效应的组合驱动固溶体进入金属状态。
The study of insulator-to-metal transitions is of interest from the viewpoint of fundamental understanding of the underlying physics, and materials at the brink of such transitions possess useful functionality. Driving this transition through compositional tuning can help engineer useful material properties. Here we study the role of disorder in the form of cation off-centering on the compositionally-controlled insulator-to-metal transition in the solid solution oxide pyrochlore (. Prior work has established site disorder by thecations shifting incoherently away from their ideal crystallographic site in the Bi end-member pyrochlore as a consequence of stereochemical activity of the lone pair of electrons. However, less is known about the consequences of such off-centering in solid solutions and its role in determining the electronic ground state. Here we demonstrate through total scattering studies that even a small substitution of Bi on the pyrochloreAsite leads to site disorder that enhances the average effective size of theA-site cation. This indirectly increases Ru-O-Ru covalency, which appears to play a crucial role in the crossover from insulating to metallic behavior in the solid solution. Further, density functional electronic structure calculations suggest the combination of primary and secondary (due to size) electronic effects of the lone pair-driven incoherent cation displacements drive the solid solution into a metallic state.