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Na9 Bi5 Os3 O24 : A Diamagnetic Oxide Featuring a Pronouncedly Jahn-Teller-Compressed Octahedral Coordination of
Gohil S Thakur1,2, Hans Reuter3, Alexey V Ushakov4
1Max Planck Institute for Chemical Physics of Solids, Nöthnitzerstr. 40, 01187, Dresden, Germany.
Abstract:
The Jahn-Teller (JT) theorem constitutes one of the most fundamental concepts in chemistry. In transition-element chemistry, the 3d4 and 3d9 configurations in octahedral complexes are particularly illustrative, where a distortion in local geometry is associated with a reduction of the electronic energy. However, there has been a lasting debate about the fact that the octahedra are found to exclusively elongate. In contrast, for Na9 Bi5 Os3 O24 , the octahedron around Os6+ (5d2 ) is heavily compressed, lifting the degeneracy of the t2g set of 5d orbitals such that in the sense of a JT compression a diamagnetic ground state results. This effect is not forced by structural constraints, the structure offers sufficient space for osmium to shift the apical oxygen atoms to a standard distance. The relevance of these findings is far reaching, since they provide new insights in the hierarchy of perturbations defining ground states of open shell electronic systems.
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