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Abstract
The authors regret that in our recent paper describing the phase transitions of the hexagonal tungsten bronze RbNbW_{2}O_{9} based on analysis of variable temperature powder neutron diffraction data [1], we (erroneously) concluded that there is no direct continuous transition between the Cmc2_{1} and P6mm structures and therefore a transition through the intermediate P6_{3}mc was proposed. While there is no reason to doubt that both the lower (Cmc2_{1}) and higher temperature (P6mm) structures are correct, the assignment of the intermediate P6_{3}mc phase at 673 K is unnecessary. This conclusion is based on two considerations: 1. On further inspection using the ISOTROPY software suite [2] we can now confirm that a direct continuous transition from P6mm to Cmc2_{1} is allowed by introduction of the A_{6}^{+} mode (in fact this tilt mode is labelled A_{6} in this transition from the noncentrosymmetric parent, P6mm, but we use A_{6}^{+} for simplicity in comparing to the notation used for the equivalent tilt mode derived from the aristotype phase, P6/mmm, Table 1 – we thank our coauthor CJH for bringing this to our attention). This pathway was not included in Fig. S2 of our original work, but a simplified version highlighting this additional transition and the transitions related to this work is now shown in Fig. 1.2. In reconsidering our original refinement of the data at 673 K in the Cmc2_{1} model (Table 1 of the original paper) we identified that this refinement had unfortunately resulted in a false minimum, whereby the sign of the A_{3}^{+} mode (A_{3} relative to the P6mm parent) had effectively been reversed. This has now been corrected and the revised Cmc2_{1} model results in a better fit to the data than P6_{3}mc at 673 K (Table 2, below).Consequently, the lattice parameters, bond lengths and distortion mode amplitudes (Figs. 4, 5 and 7 in the original article) were redetermined for all temperatures up to 673 K and updated Figs. 2–4 and Table 3 reflect these minor changes. The general trends observed in each parameter are consistent with those previously reported and support the assignment of Cmc2_{1} rather than P6_{3}mc at 673 K, and then a continuous transition to P6mm. Extrapolation of the A_{6}^{+} and Γ_{5}⁻ modes using a weighted power law (Fig. 4b), similar to that carried out originally, indicates the transition from Cmc2_{1} to P6mm corresponding to loss of octahedral tilting occurs at ~680 and ~690 K, respectively. The critical exponents are β = 0.354 and 0.476 with fit constants of A = 0.091 and 0.017, respectively. Considering this, the key point of this corrigendum is that the transition sequence can now be summarised (with no requirement for the intermediate P6_{3}mc phase) as: [Formula presented] The authors would like to apologise for any inconvenience caused.
Original language  English 

Article number  121548 
Journal  Journal of Solid State Chemistry 
Volume  291 
DOIs 

Publication status  Published  Nov 2020 
Keywords
 Hexagonal tungsten bronze
 Phase transitions
 Powder neutron diffraction
 Proper ferroelectricity
 Symmetrymode analysis
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Dive into the research topics of 'Corrigendum to: “Phase transitions in the hexagonal tungsten bronze RbNbW_{2}O_{9}” [J. Solid State Chem. 286 (2020) 121275]'. Together they form a unique fingerprint.Projects
 1 Finished

New Horizon in Nanoscale: Ferrolectric, Ferroelastic and Multiferroic Domain Walls: a New Horizon in Nanoscale Functional Materials
Scott, J. F. & Morrison, F.
1/04/17 → 31/03/21
Project: Standard