scholarly journals Rigid unit modes insp−sp2hybridized carbon systems: Origin of negative thermal expansion

2015 ◽  
Vol 92 (24) ◽  
Author(s):  
Cheol-Woon Kim ◽  
Seoung-Hun Kang ◽  
Young-Kyun Kwon
Keyword(s):  
Thermal Expansion ◽  
Negative Thermal Expansion ◽  
Rigid Unit Modes

Rigid unit modes and the negative thermal expansion in ZrW2O8

1997 ◽  
Vol 61 (1-4) ◽  
pp. 141-153 ◽  
Author(s):  
Alexandra K.A. Pryde ◽  
Kenton D. Hammonds ◽  
Martin T. Dove ◽  
Volker Heine ◽  
Julian D. Gale ◽  
...  
Keyword(s):  
Thermal Expansion ◽  
Negative Thermal Expansion ◽  
Rigid Unit Modes

Negative Thermal Expansion inZrW2O8: Mechanisms, Rigid Unit Modes, and Neutron Total Scattering

2005 ◽  
Vol 95 (25) ◽  
Author(s):  
Matthew G. Tucker ◽  
Andrew L. Goodwin ◽  
Martin T. Dove ◽  
David A. Keen ◽  
Stephen A. Wells ◽  
...  
Keyword(s):  
Thermal Expansion ◽  
Negative Thermal Expansion ◽  
Total Scattering ◽  
Rigid Unit Modes ◽  
Neutron Total Scattering

scholarly journals Contrasting compressibility trends in layered structures Ag(tcm) and Ni(CN)2

2014 ◽  
Vol 70 (a1) ◽  
pp. C266-C266 ◽  
Author(s):  
Jasper Adamson ◽  
Sarah Hodgson ◽  
Sarah Hunt ◽  
Matthew Cliffe ◽  
Andrew Cairns ◽  
...  
Keyword(s):  
Thermal Expansion ◽  
Hydrostatic Pressure ◽  
Negative Thermal Expansion ◽  
Layered Structures ◽  
Phonon Modes ◽  
Direction Parallel ◽  
Displacement Pattern ◽  
Rigid Unit Modes ◽  
Effective Layer ◽  
Linear Compressibility

Ag(tcm) (tcm = tricyanomethanide) and Ni(CN)2 are layered structures. Both these materials exhibit area negative thermal expansion (area-NTE) due to 'rippling' of the layers - a displacement pattern that causes the interlayer separation to increase and the effective layer area to decrease (Fig. 1a). We have shown that Ag(tcm) shows negative area compressibility (NAC) under hydrostatic pressure. The latter can be attributed to the rippling phenomenon: when hydrostatic pressure is applied, the effective layer area increases (Fig. 1a). On the contrary, Ni(CN)2 shows shows positive linear compressibility in all directions, albeit much more strongly along the stacking axis than in any direction parallel to the square-grid sheets. This is attributed to transverse phonon modes within the Ni(CN)2 sheets, which can be visualised as 'tilting' of the rigid unit modes (RUMs) (Fig. 1b). A discussion of relating such behaviour to the Grüneisen parameters is undertaken in this study.

scholarly journals Maximizing negative thermal expansion via rigid unit modes: a geometry-based approach

2015 ◽  
Vol 471 (2179) ◽  
pp. 20150188 ◽  
Author(s):  
J. N. Grima ◽  
M. Bajada ◽  
S. Scerri ◽  
D. Attard ◽  
K. K. Dudek ◽  
...  
Keyword(s):  
Thermal Expansion ◽  
Mechanical Characteristics ◽  
Negative Thermal Expansion ◽  
Analytical Models ◽  
Geometrical Parameters ◽  
New Materials ◽  
Pore Sizes ◽  
Negative Poisson's Ratio ◽  
Internal Angle ◽  
Rigid Unit Modes

Existent rigid unit mode (RUM) models based on rotating squares, which may explain the phenomenon of negative thermal expansion (NTE), are generalized so as to assess the NTE potential for novel systems made from rectangular or rhombic rigid units. Analytical models for the area coefficients of thermal expansion (CTE) of these innovative networks are derived in an attempt to determine the optimal geometrical parameters and connectivity for maximum NTE. It was found that all systems exhibit NTE, the extent of which is determined by the shape and connectivity of the elemental rigid units (side lengths ratio or internal angle). It was also found that some of the networks proposed here should exhibit significantly superior NTE properties when compared with the well-known network of squares, and that for optimal NTE characteristics, pencil-like rigid units should be used rather than square-shaped ones, as these permit larger pore sizes that are more conducive to NTE. All this compliments earlier work on the negative Poisson's ratio (auxetic) potential of such systems and may provide a route for the design of new materials exhibiting superior thermo-mechanical characteristics including specifically tailored CTEs or giant NTE characteristics.

Polarization- and Strain-Mediated Control of Negative Thermal Expansion and Ferroelasticity in BiInO3–BiZn1/2Ti1/2O3

2021 ◽  
Vol 33 (4) ◽  
pp. 1498-1505
Author(s):  
Takumi Nishikubo ◽  
Takahiro Ogata ◽  
Lalitha Kodumudi Venkataraman ◽  
Daniel Isaia ◽  
Zhao Pan ◽  
...  
Keyword(s):  
Thermal Expansion ◽  
Negative Thermal Expansion
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