Black phosphorene exhibiting negative thermal expansion and negative linear compressibility

Dicyanometallate coordination polymers show a number of desirable properties: piezoelectricity, record-breaking negative thermal expansion (NTE) and negative linear compressibility (NLC), vapochromism, and luminescence. Despite this, the rules governing the structural trends arising from the use of this roughly 10 Å linker, [M(CN)2]- where M = Cu, Ag, or Au, are relatively poorly explored. This talk is concerned both with mapping the composition–connectivity relationship in these systems and understanding the role of guest cation size/shape mismatch. We show that using guest cations that would be a poor fit for the void-space in commonly adopted topologies can lead to two structural phenomena exemplified in compounds reported here. Firstly, the adoption of unusual topologies, such as 5-connected frameworks e.g.[Bu4N]0.5Cd[Ag(CN)2]2.5 and secondly, correlated structural disorder as seen in molecular perovskite analogues [Bu4N]M'[Au(CN)2]3 where M' = Cd, Mn, Fe.

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Uniaxial Negative Thermal Expansion, Negative Linear Compressibility, and Negative Poisson’s Ratio Induced by Specific Topology in Zn[Au(CN)2]2

Inorganic Chemistry ◽

10.1021/acs.inorgchem.7b02416 ◽

2017 ◽

Vol 56 (24) ◽

pp. 15101-15109 ◽

Cited By ~ 7

Author(s):

Lei Wang ◽

Hubin Luo ◽

Shenghua Deng ◽

Ying Sun ◽

Cong Wang

Keyword(s):

Thermal Expansion ◽

Poisson’S Ratio ◽

Negative Thermal Expansion ◽

Poisson's Ratio ◽

Negative Poisson’S Ratio ◽

Negative Poisson's Ratio ◽

Linear Compressibility

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

Acta Crystallographica Section A Foundations and Advances ◽

10.1107/s2053273314097332 ◽

2014 ◽

Vol 70 (a1) ◽

pp. C266-C266 ◽

Cited By ~ 1

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.

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