Structure, phase transition and negative thermal expansion in ammoniated ZrW<sub>2</sub>O<sub>8</sub>

Cao, Weigang; Huang, Q.; Rong, Yangchun; Wang, You; Deng, Jinxia; Chen, Jun; Xing, Xianran

doi:10.1039/c5qi00292c

Cited by 21 publications

(13 citation statements)

References 34 publications

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“…A number of theoretical and experimental studies [1,42,57,113,114] have been performed to identify these kinds of materials and understand the phenomenon of anomalous thermal expansion.…”

Section: Introductionmentioning

confidence: 99%

Phonons and anomalous thermal expansion behaviour in crystalline solids

Mittal

Chaplot

2018

Progress in Materials Science

124

105

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Anomalous thermal expansion behaviour of several open frame-work compounds has been extensively investigated using the techniques of inelastic neutron scattering and lattice dynamics. These compounds involve increasing level of structural complexity and flexibility, which leads to increased values of thermal expansion coefficients approaching colossal values. In several compounds, neutron inelastic scattering experiments have produced quantitative estimates of the anharmonicity of phonons over a range of low energies, and thereby explained the observed thermal expansion quantitatively. The anharmonicity is found to be an order of magnitude larger than that in usual materials. Lattice dynamical calculations have correctly predicted the observed anharmonicity in the neutron experiments and revealed the overall nature of phonons involved. In compounds showing negative thermal expansion, the phonons responsible have rather low energies up to 10 meV. In most compounds, the anharmonic phonons span all over the Brillouin zone, while in some cases the specific phonons are limited to certain wave-vectors. The nature of specific phonons responsible for anomalous behavior is found to be different in all these compounds.These phonons generally involve transverse vibrations, librations and internal distortions of the polyhedral units. The paper reviews recent advances in the understanding of anomalous thermal expansion behaviour.

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“…A number of theoretical and experimental studies [1,42,57,113,114] have been performed to identify these kinds of materials and understand the phenomenon of anomalous thermal expansion.…”

Section: Introductionmentioning

confidence: 99%

Phonons and anomalous thermal expansion behaviour in crystalline solids

Mittal

Chaplot

2018

Progress in Materials Science

124

105

View full text Add to dashboard Cite

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“…The research on materials with anomalous thermal expansion has become a popular area of interest in material science during past three decades [1][2][3][4][5][6][7][8][9][10][11][12] . The main reason for this increase in popularity is the potential usage of these compounds in various industrial applications.…”

Section: Introductionmentioning

confidence: 99%

Investigating anomalous thermal expansion of copper halides by inelastic neutron scattering and ab initio phonon calculations

Gopakumar

Gupta

Mittal

et al. 2017

Phys. Chem. Chem. Phys.

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We investigate detailed lattice dynamics of copper halides CuX (X=Cl, Br, I) using neutron inelastic scattering measurements and ab-initio calculations aimed at a comparative study of their thermal expansion behavior. We identify the low energy phonons which soften with pressure and are responsible for negative thermal expansion. The eigenvector analysis of these modes suggests that softening of the transverse-acoustic modes would lead to NTE in these compounds. The calculations are in very good agreement with our measurements of phonon spectra and thermal expansion behavior as reported in the literature. Our calculations at high pressure further reveal that large difference in negative thermal expansion behavior in these compounds is associated with the difference of the unit cell volume.

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“…So there is a choice of three possible orientations for each of the four water molecules to be placed in a single unit cell. This situation contrasts that of NH 3 binding in ZrW 2 O 8 •NH 3 , for which NH 3 orientations are ordered and P 2 1 3 symmetry is maintained [32]-the molecular point symmetry of NH 3 (3m) being a supergroup of the 4a site symmetry (3) [33]. Instead the arrangement of H 2 O molecules that results in the least severe symmetry low-ering gives P 2 1 2 1 2 1 symmetry.…”

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confidence: 99%

Negative Hydration Expansion in ZrW2O8 : Microscopic Mechanism, Spaghetti Dynamics, and Negative Thermal Expansion

et al. 2018

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We use a combination of x-ray diffraction, total scattering, and quantum mechanical calculations to determine the mechanism responsible for hydration-driven contraction in ZrW_{2}O_{8}. The inclusion of H_{2}O molecules within the ZrW_{2}O_{8} network drives the concerted formation of new W─O bonds to give one-dimensional (─W─O─)_{n} strings. The topology of the ZrW_{2}O_{8} network is such that there is no unique choice for the string trajectories: the same local changes in coordination can propagate with a large number of different periodicities. Consequently, ZrW_{2}O_{8}·H_{2}O is heavily disordered, with each configuration of strings forming a dense aperiodic "spaghetti." This new connectivity contracts the unit cell via large shifts in the Zr and W atom positions. Fluctuations of the undistorted parent structure towards this spaghetti phase emerge as the key negative thermal expansion (NTE) phonon modes in ZrW_{2}O_{8} itself. The large relative density of NTE phonon modes in ZrW_{2}O_{8} actually reflects the degeneracy of volume-contracting spaghetti excitations, itself a function of the particular topology of this remarkable material.

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Structure, phase transition and negative thermal expansion in ammoniated ZrW₂O₈

Abstract: The local structural changes of ZrW2O8 after ammoniation treatment.

Cited by 21 publications

References 34 publications

Phonons and anomalous thermal expansion behaviour in crystalline solids

Phonons and anomalous thermal expansion behaviour in crystalline solids

Investigating anomalous thermal expansion of copper halides by inelastic neutron scattering and ab initio phonon calculations

Negative Hydration Expansion in ZrW2O8 : Microscopic Mechanism, Spaghetti Dynamics, and Negative Thermal Expansion

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Structure, phase transition and negative thermal expansion in ammoniated ZrW2O8

Abstract: The local structural changes of ZrW2O8 after ammoniation treatment.

Cited by 21 publications

References 34 publications

Phonons and anomalous thermal expansion behaviour in crystalline solids

Phonons and anomalous thermal expansion behaviour in crystalline solids

Investigating anomalous thermal expansion of copper halides by inelastic neutron scattering and ab initio phonon calculations

Negative Hydration Expansion in ZrW2O8 : Microscopic Mechanism, Spaghetti Dynamics, and Negative Thermal Expansion

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Product

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Structure, phase transition and negative thermal expansion in ammoniated ZrW₂O₈