Structure of russellite: Origin of ferroelectricity and the effect of stereoactive lone electron pair on the structure

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Marco E. Ciriotti
Messaggi: 24488
Iscritto il: ven 25 giu, 2004 11:31
Località: via San Pietro, 55 I-10073 Devesi/Cirié TO - Italy
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Structure of russellite: Origin of ferroelectricity and the effect of stereoactive lone electron pair on the structure

Messaggio da Marco E. Ciriotti » mar 24 apr, 2018 9:15

Prossima pubblicazione.

Referenza:
▪ Okudera, H., Sakai, Y., Yamagata, K., Takeda, H. (2018): Structure of russellite (Bi2WO6): Origin of ferroelectricity and the effect of stereoactive lone electron pair on the structure. Acta Crystallographica, B74, (in press).

Abstract:
The structure of low temperature-polar (orthorhombic) phase of russellite (Bi2WO6) was re-examined with a single-crystal X-ray diffraction. The position of stereochemically active lone pair of bis­muth was found on the line running through the Bi sites along the b-axis direction. The cause of the ferroelectricity of the compound was ascribed to the strong demand of bis­muth to form shorter Bi—O bonds, and this resulted in the cooperative shift of tungsten leaving its ligands left behind.
Marco E. Ciriotti

«Things are interesting only in so far as they relate themselves to other things»

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Marco E. Ciriotti
Messaggi: 24488
Iscritto il: ven 25 giu, 2004 11:31
Località: via San Pietro, 55 I-10073 Devesi/Cirié TO - Italy
Contatta:

Re: Structure of russellite: Origin of ferroelectricity and the effect of stereoactive lone electron pair on the structu

Messaggio da Marco E. Ciriotti » lun 04 giu, 2018 15:23

Pubblicazione effettuata.

Referenza:
▪ Okudera, H., Sakai, Y., Yamagata, K., Takeda, H. (2018): Structure of russellite (Bi2WO6): Origin of ferroelectricity and the effect of stereoactive lone electron pair on the structure. Acta Crystallographica, B74, 295-303.

Abstract:
The structure of the low‐temperature polar (orthorhombic) phase of russellite (Bi2WO6) was examined on artificial specimens with precise single‐crystal X‐ray diffraction experiments. The final atomic arrangement thus obtained was identical to that reported by Knight [Miner. Mag. (1992), 56, 399–409] with powder neutron diffraction. The residual density attributable to a stereochemically‐active lone pair of electrons of bismuth was prominent at approximately the centre of a larger cap of BiO8 square antiprisms, that is on the line from the Bi sites to an adjacent WO42− slab along the b‐axis direction. Quite uneven Bi—O distances and the formation of a vacant coordination hemisphere (within 3 Å) should, therefore, be ascribed to the strong demand of bismuth to form shorter Bi—O bonds to use up its electrostatic charge within its coordination environment. The shift of bismuth along −c propagates via the correlated shift of the W site and these cooperative shifts cause ferroelectricity in the compound. This propagation was easily effected by the intrusion of molecules such as acetone into the structure.
Marco E. Ciriotti

«Things are interesting only in so far as they relate themselves to other things»

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