Origin of the negative thermal expansion in ZrW2O8 and ZrV2O7

被引:299
作者
Pryde, AKA
Hammonds, KD
Dove, MT
Heine, V
Gale, JD
Warren, MC
机构
[1] UNIV CAMBRIDGE, DEPT EARTH SCI, CAMBRIDGE CB2 3EQ, ENGLAND
[2] UNIV CAMBRIDGE, CAVENDISH LAB, CAMBRIDGE CB3 0HE, ENGLAND
[3] UNIV LONDON IMPERIAL COLL SCI TECHNOL & MED, DEPT CHEM, LONDON SW7 2AY, ENGLAND
[4] UNIV EDINBURGH, DEPT PHYS & ASTRON, EDINBURGH EH9 3JZ, MIDLOTHIAN, SCOTLAND
关键词
D O I
10.1088/0953-8984/8/50/023
中图分类号
O469 [凝聚态物理学];
学科分类号
070205 ;
摘要
The negative thermal expansion recently observed over a wide range of temperatures in ZrW2O8 may be attributed to the existence of low-frequency phonon modes which can propagate with no distortions of the WO4 tetrahedra and ZrO6 octahedra, the so-called 'rigid unit modes'. Using methods developed for the study of similar modes in silicates we have located the surfaces of these modes in wave-vector space. The rigid-unit mode interpretation accounts for the weak effect of the 430 K structural phase transition on the negative thermal expansion, provided that the disordered phase does not involve formation of W2O7 and W2O9 complexes. On the other hand, the crystal structure of the related material ZrV2O7 is cross braced by pairs of linked tetrahedra and is therefore significantly less flexible. In this case a qualitatively different mechanism may be responsible for the negative thermal expansion observed in ZrV2O7.
引用
收藏
页码:10973 / 10982
页数:10
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