Symmetry and twins in the monophosphate tungsten bronze series (P02)4(W03)2m (2 < or = m < or = 14) - Université de Lille Accéder directement au contenu
Article Dans Une Revue Acta Crystallographica Section B : Structural Science [1968-2013] Année : 2000

Symmetry and twins in the monophosphate tungsten bronze series (P02)4(W03)2m (2 < or = m < or = 14)

Résumé

Monophosphate tungsten bronze with pentagonal tunnels (PO2)4(WO3)2m are low-dimensional materials with charge density wave (CDW)-type electron instabilities. Two forms of the structure can thus be expected for all the members of the series: a low-temperature form (LT) corresponding to the CDW state and a high-temperature form (HT) corresponding to a normal metallic state. The HT form is described here for m = 9 and compared with that of the m = 5 and m = 7 counterparts. It is shown that a systematic twin phenomenon must be taken into account for HT members because of two possible configurations of the tilting mode of WO6 octahedra. The structure is also compared with that of m = 10, which exhibits the modulated CDW–LT form at room temperature. Owing to two possible polarization directions of the segments built of m WO6 octahedra, a twin phenomenon is also encountered in the LT forms. A review of all the structures known at present (m = 2, 4, 5, 6, 7, 8, 9, 10, 12) leads us to propose a structural law based on the building mode of WO6 octahedra in WO3-type slabs to explain the symmetry changes observed between even and odd members of the series.

Domaines

Chimie

Dates et versions

hal-04560315 , version 1 (26-04-2024)

Identifiants

Citer

Pascal Roussel, P. Labbe, D. Groult. Symmetry and twins in the monophosphate tungsten bronze series (P02)4(W03)2m (2 < or = m < or = 14). Acta Crystallographica Section B : Structural Science [1968-2013], 2000, Acta Crystallographica Section B : Structural Science [1968-2013], 56, pp.377-91. ⟨10.1107/s0108768199016195⟩. ⟨hal-04560315⟩
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