Rigid unit modes and the negative thermal expansion in ZrW2O8

Rigid unit modes and the negative thermal expansion in ZrW2O8

ZrW 2 O 8 has a negative coefficient of thermal expansion from 0.3 K to its decomposition temperature around 1050 K. The negative thermal expansion is isotropic and is not disrupted by the structural phase transition at 430 K. A complicated distribution in reciprocal space of Rigid Unit Mode (RUM) p...

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Veröffentlicht in:Phase transitions 1997-05, Vol.61 (1-4), p.141-153
Hauptverfasser: Pryde, Alexandra K.A., Hammonds, Kenton D., Dove, Martin T., Heine, Volker, Gale, Julian D., Warren, Michele C.
Format: Artikel
Sprache:eng
Schlagworte:
Negative thermal expansion
Rigid Unit Modes
Zirconium Tungstate
ZrW
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Zusammenfassung:ZrW 2 O 8 has a negative coefficient of thermal expansion from 0.3 K to its decomposition temperature around 1050 K. The negative thermal expansion is isotropic and is not disrupted by the structural phase transition at 430 K. A complicated distribution in reciprocal space of Rigid Unit Mode (RUM) phonons has been found for ZrW 2 O 8 using Lattice Dynamics. The RUMS are very low energy phonons which cause collective rotations of ZrO 6 octahedra and WO 4 tetrahedra within the crystal structure. These distortions enable ZrW 2 O 8 to contract upon heating.
ISSN:0141-1594
1029-0338
DOI:10.1080/01411599708223734