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![b logo](https://journals.iucr.org/logos/jicons/b_36x36.png)
Group-theoretical methods are used to enumerate the structures of ordered perovskites, in which 1:2 and 1:3 ordering of B and B′ cations is considered in combination with the ubiquitous BX6 (or B′X6) octahedral tilting. The cation ordering on the B-cation site is described by irreducible representations of the
space group of the cubic aristotype: Λ1 (k = 1/3,1/3,1/3) for the cation ordering pattern in the 1:2 compound A3BB
X9 and
(k = 1/2,1/2,0) for the cation ordering in the 1:3 compound A4BB
X12. The octahedral tilting is mediated by the irreducible representations
and
. Ten distinct structures have been identified in the 1:2 case and 11 structures for 1:3.
![Pm\bar 3m](http://journals.iucr.org/b/issues/2004/06/00/ws5012//teximages/ws5012fi3.gif)
![_2^{\prime}](http://journals.iucr.org/b/issues/2004/06/00/ws5012//teximages/ws5012fi1.gif)
![M_1^ +](http://journals.iucr.org/b/issues/2004/06/00/ws5012//teximages/ws5012fi5.gif)
![_3^{\prime}](http://journals.iucr.org/b/issues/2004/06/00/ws5012//teximages/ws5012fi2.gif)
![M_3^ +](http://journals.iucr.org/b/issues/2004/06/00/ws5012//teximages/ws5012fi7.gif)
![R_4^ +](http://journals.iucr.org/b/issues/2004/06/00/ws5012//teximages/ws5012fi8.gif)