Elastic anisotropy and extreme Poisson’s ratios in single crystals

Lethbridge, Zoe A. D.; Walton, Richard I.; Marmier, A.; Smith, Christopher W.; Evans, K.

doi:10.1016/j.actamat.2010.08.006

Cited by 144 publications

(105 citation statements)

References 46 publications

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“…Following a trend similar to that of the reference sample, the proportions decrease rapidly above these classifications, with few materials displaying type 3 or class C auxeticity, with one notable exception, discussed later. Comparison of the minimum and maximum calculated Poisson's ratio with elastic anisotropy confirms the work of Lethbridge et al 8 It was found that the extreme Poisson's ratio all lie on two families of curves approximately symmetrical around a single point of intersection at A* = 1, where A* is the Ledbetter anisotropy measure defined as the square of the maximum shear-sound-wave velocity divided by the square of the minimum shear-sound-wave velocity 35 . Fig.…”

Section: α-Cristobalitesupporting

confidence: 70%

“…Firstly, zeolites in particular have historically received considerable interest due to their very low density and potential use as catalysts 5 or molecular sieves 6,7 . Early studies of their mechanical properties have been far from systematic and in light of recent results 8,9 it is timely to revisit auxeticity in silicates in general, and zeolites in particular, to compare their mechanical properties with those of other crystalline materials. Secondly, it has been recognised that, singularly among single crystals, α-cristobalite is auxetic in a large directions range 10 ; a logical place to search for materials with equally exceptional properties is amongst other silicates, especially largely unexplored pure silica zeolites.…”

Section: Introductionmentioning

confidence: 99%

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A systematic typology for negative Poisson's ratio materials and the prediction of complete auxeticity in pure silica zeolite JST

Siddorn

Coudert

Evans

et al. 2015

Phys. Chem. Chem. Phys.

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A systematic typology for negative Poisson's ratio materials and the prediction of complete auxeticity in pure silica zeolite JST. Physical Chemistry Chemical Physics, 17 (27). pp. 17927-17933. ISSN 1463-9076 Available from: http://eprints.uwe.ac.uk/29078We recommend you cite the published version. The publisher's URL is: http://dx.doi.org/10.1039/C5CP01168JRefereed: Yes (no note) Disclaimer UWE has obtained warranties from all depositors as to their title in the material deposited and as to their right to deposit such material. UWE makes no representation or warranties of commercial utility, title, or fitness for a particular purpose or any other warranty, express or implied in respect of any material deposited. UWE makes no representation that the use of the materials will not infringe any patent, copyright, trademark or other property or proprietary rights. UWE accepts no liability for any infringement of intellectual property rights in any material deposited but will remove such material from public view pending investigation in the event of an allegation of any such infringement. Single crystals can commonly have negative Poisson's ratio in a few directions; however more generalised auxeticity is rarer. We propose a typology to distinguish auxetic materials. We characterise numerous single crystals and demonstrate that partial auxeticity occurs for around 37%. We find average auxeticity to be limited to α-cristobalite and no example of complete auxeticity. We simulate two hundreds pure silica zeolites with empirical potentials and quantum chemistry methods, and for the first time identify complete auxeticity in a zeolite network, JST. IntroductionThe main aims of this study are to develop a convenient typology of auxetic behaviour in materials, to characterise the Poisson's ratio of pure silica zeolites and to identify structures with exceptional values. The Poisson's ratio for anisotropic materials is complex, a function of three variables, two defining a longitudinal direction, one a transverse one. The adjective "auxetic", describing the existence of a negative Poisson's ratio (NPR) 1 , is too limited to describe fundamentally different situations, from single crystals where NPR occurs for very specific directions, to isotropic foams where NPR is present for all directions. Therefore an important objective has been to develop a finergrained typology of auxetic properties to discriminate between the relatively common existence of negative Poisson's ratios in a few narrowly defined combinations of longitudinal and transverse directions and the rarer, more comprehensive cases. BackgroundOf the four elastic constants used to describe isotropic materials, Young's modulus (E), bulk modulus (K), shear modulus (G) and Poisson's ratio (ν), it is the Poisson's ratio that has historically been the least explored 2,3 . It can be associated with some interesting and unusual properties, particularly when in a range not normally encountered. Defined as the ratio of transverse to longitudinal strain in a structure or ma...

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Section: α-Cristobalitesupporting

confidence: 70%

Section: Introductionmentioning

confidence: 99%

A systematic typology for negative Poisson's ratio materials and the prediction of complete auxeticity in pure silica zeolite JST

Siddorn

Coudert

Evans

et al. 2015

Phys. Chem. Chem. Phys.

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“…Among structural networks are molecular networks 3 , hierarchical structures 4 , composites 5 and hinged structures 22,23 . Some materials exhibit auxetic properties as they are stretched or compressed in a proper direction [6][7][8][9][24][25][26][27][28][29][30] . For example, Baughman et al 7 reported that 69% of all cubic materials exhibit a negative Poisson's ratio along the [1 10]-direction when they are subjected to stretching along the [110]-direction.…”

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confidence: 99%

Negative Poisson’s ratios in metal nanoplates

et al. 2014

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The Poisson's ratio is a fundamental measure of the elastic-deformation behaviour of materials. Although negative Poisson's ratios are theoretically possible, they were believed to be rare in nature. In particular, while some studies have focused on finding or producing materials with a negative Poisson's ratio in bulk form, there has been no such study for nanoscale materials. Here we provide numerical and theoretical evidence that negative Poisson's ratios are found in several nanoscale metal plates under finite strains. Furthermore, under the same conditions of crystal orientation and loading direction, materials with a positive Poisson's ratio in bulk form can display a negative Poisson's ratio when the material's thickness approaches the nanometer scale. We show that this behaviour originates from a unique surface effect that induces a finite compressive stress inside the nanoplates, and from a phase transformation that causes the Poisson's ratio to depend strongly on the amount of stretch.

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“…However, the much lower νmin of MAF-7 than ZIF-8 implies that such an electron effect also negatively contribute to the framework stability enhancement under axial tensile or compression stresses along some directions. Now, we focus on the Poisson's ratio (ν) which is defined as the negative ratio of the transverse strain (ε j ) to the longitudinal strain (ε i ), i.e., ν = −ε j /ε i [24]. Poisson's ratio ν is expressed as…”

Section: Resultsmentioning

confidence: 99%

“…As such, the same pair of opposing shear stresses τ applied on the (100) or (110) plane can generate larger deformation along the <110> than <100> direction, hence, leading to G min along <110> while G max along <100> direction. Now, we focus on the Poisson's ratio (ν) which is defined as the negative ratio of the transverse strain (ɛj) to the longitudinal strain (ɛi), i.e., ν = −ɛj/ɛi [24]. Poisson's ratio ν is expressed as ν ′ ′ ′ ⁄ in a cubic system [19].…”

Section: Resultsmentioning

confidence: 99%

Enhanced Framework Rigidity of a Zeolitic Metal-Azolate via Ligand Substitution

et al. 2017

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Abstract:The elastic properties of a zeolitic metal-azolate framework, Zn(mtz) 2 (MAF-7, mtz − = 3-methyl-1,2,4-triazolate), have been examined from the view point of the first principles calculations and experiments. Our results demonstrate that the three independent elastic constants of MAF-7 are about 5.0-73.3% higher than those of ZIF-8, though they are isomorphic. The electron-donating effect of the nitrogen atom at the 2-position in mtz-ring dominantly accounts for such a prominent difference. The detailed analysis of the full elastic tensors reveals that the volume moduli, shear moduli, and Poisson's ratios of MAF-7 are about 3.4% to 20.1%, 3.2% to 20.6%, and −30.3% to 12.3% higher than those of ZIF-8. The underlying structural reasons were discussed to explain the anisotropic difference of those properties. Moreover, the conclusion deduced from first-principle calculations was also been verified by nanoindentation and high-pressure synchrotron X-ray diffraction measurements.

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Elastic anisotropy and extreme Poisson’s ratios in single crystals

Cited by 144 publications

References 46 publications

A systematic typology for negative Poisson's ratio materials and the prediction of complete auxeticity in pure silica zeolite JST

A systematic typology for negative Poisson's ratio materials and the prediction of complete auxeticity in pure silica zeolite JST

Negative Poisson’s ratios in metal nanoplates

Enhanced Framework Rigidity of a Zeolitic Metal-Azolate via Ligand Substitution

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