Controlling multiple orderings in metal thiocyanate molecular perovskites A x {Ni[Bi(SCN) 6 ]}

We report four new A-site vacancy ordered thiocyanate double double perovskites, , A = K , NH , CH (NH ) (MeNH ) and C(NH ) (Gua ), including the first examples of thiocyanate perovskites containing organic A-site cations. We show, using a combination of X-ray and neutron diffraction, that the struc...

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Bibliographic Details
Published in:Chemical science (Cambridge) 2021-01, Vol.12 (10), p.3516-3525
Main Authors: Lee, Jie Yie, Ling, Sanliang, Argent, Stephen P, Senn, Mark S, Cañadillas-Delgado, Laura, Cliffe, Matthew J
Format: Article
Language:English
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Summary:We report four new A-site vacancy ordered thiocyanate double double perovskites, , A = K , NH , CH (NH ) (MeNH ) and C(NH ) (Gua ), including the first examples of thiocyanate perovskites containing organic A-site cations. We show, using a combination of X-ray and neutron diffraction, that the structure of these frameworks depends on the A-site cation, and that these frameworks possess complex vacancy-ordering patterns and cooperative octahedral tilts distinctly different from atomic perovskites. Density functional theory calculations uncover the energetic origin of these complex orders and allow us to propose a simple rule to predict favoured A-site cation orderings for a given tilt sequence. We use these insights, in combination with symmetry mode analyses, to show that these complex orders suggest a new route to non-centrosymmetric perovskites, and mean this family of materials could contain excellent candidates for piezo- and ferroelectric applications.
ISSN:2041-6520
2041-6539
DOI:10.1039/D0SC06619B