Howard Christopher J, Carpenter Michael A
Department of Earth Sciences, University of Cambridge, Downing Street, Cambridge CB2 3EQ, England.
Acta Crystallogr B. 2010 Feb;66(Pt 1):40-50. doi: 10.1107/S0108768109048010. Epub 2009 Dec 12.
Computer-based group-theoretical methods are used to enumerate structures arising in A(2)BB'X(6) perovskites, with either rock-salt or checkerboard ordering of the B and B' cations, under the additional assumption that one of these two cations is Jahn-Teller active and thereby induces a distortion of the BX(6) (or B'X(6)) octahedron. The requirement to match the pattern of Jahn-Teller distortions to the cation ordering implies that the corresponding irreducible representations should be associated with the same point in the Brillouin zone. Effects of BX(6) (and B'X(6)) octahedral tilting are included in the usual way. Finally, an analysis is presented of more complex models of ordering and distortion as might lead to the doubling of the long axis of the common Pnma perovskite, observed in systems such as Pr(1-x)Ca(x)MnO(3) (x approximately 0.5). The structural hierarchies derived in this work should prove useful in interpreting experimental results.
基于计算机的群论方法用于枚举A(2)BB'X(6)钙钛矿中出现的结构，其中B和B'阳离子具有岩盐或棋盘状有序排列，并额外假设这两种阳离子之一是 Jahn-Teller 活性的，从而导致BX(6)（或B'X(6)）八面体发生畸变。将 Jahn-Teller 畸变模式与阳离子有序排列相匹配的要求意味着相应的不可约表示应与布里渊区中的同一点相关联。BX(6)（和B'X(6)）八面体倾斜的影响以通常的方式包含在内。最后，对更复杂的有序和畸变模型进行了分析，这些模型可能导致常见的Pnma钙钛矿长轴加倍，这在诸如Pr(1-x)Ca(x)MnO(3)（x约为0.5）的系统中观察到。这项工作中得出的结构层次应该有助于解释实验结果。
