Normal-mode analysis of the structures of perovskites with tilted octahedra. Erratum

There is an error in the mode assignment for hettotype 9, [a−b+a−], discussed in the paper by Darlington [Acta Cryst. (2002). A58, 6671], which has been pointed out by Dr Kevin Knight, Rutherford Appleton Laboratory, Didcot, Oxon, England. In this paper, a mode involving displacements of the anions of hettotype 9 was labelled [(½, 0, ½), M1] rather than [(½, 0, ½), M2]. Both modes involve plus‐like distortion of the octahedra. In the corrected Tables 1–4 shown below, this mode, which is only found in hettotype 9, has been labelled K2 rather than H2. Therefore, there are not seven but eight normal modes of the cubic phase required to describe the displacements found in the nine hettotypes considered. The weights of K2 in all the materials examined in the original paper with the structure of hettotype 9 [labelled W(H1) in the original Table 4] are correct, unaltered by the change in the labelling of the mode. It should be noted that [(½, 0, ½), M2] is a longitudinal mode – the seven other modes are all transverse. The weights of K2 are not significantly different from zero in the 15 structures examined.