Brillouin spectroscopy on doped SmS

Schärer, Urs; Wächter, P.

doi:10.1016/s0921-4526(96)00817-4

Cited by 7 publications

(9 citation statements)

References 8 publications

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“…On the other hand, for the SmS doped with lanthanum, Sm 75 La 25 S, at room temperature and under atmospheric pressure (i.e. $P\approx 0\,{\rm GPa}$ ) the elastic constants are $C_{11} = 91,C_{12} = {-} 26,C_{44} = 28$ 18. What means now $X = 4.5,Y = 0.5223$ and consequently according to Figs.…”

Section: Extreme Poisson's Ratiomentioning

confidence: 92%

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Auxeticity of cubic materials under pressure

Brańka

Heyes

Wojciechowski

2010

Physica Status Solidi (b)

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The global maximum and global minimum Poisson's ratio (PR) surfaces, regions of different auxetic behaviour and the domains of the different extreme directions of cubic materials are shown and discussed in terms of the elastic moduli ratios, X ¼ G=K; Y ¼ G=W, where K is the bulk modulus and G; W are shear moduli. A straightforward way is given to classify any cubic material as being auxetic, nonauxetic and partially auxetic, as well as calculating its extreme PR values. A decomposition of the XY plane with the elastic constant ratio l ¼ C 12 =C 44 is introduced to facilitate the interpretation of cubic materials under hydrostatic pressure, P > 0, and isotropic tension, P < 0, which are two qualitatively different situations. Using this representation it is demonstrated that cubic materials with l > 0 can be auxetic only under 'negative' pressure (P < 0). It is shown that the influence of pressure on the auxetic behaviour is different for the positive and negative l cases. In particular, a cubic material with 0 > l > À1 may be auxetic at negative as well as positive pressure. The work demonstrates the crucial role of P in obtaining desired auxetic behaviour. Microscopic mechanisms which tune the cubic system to targeted regions in the XY plane are investigated with a fcc crystal of particles interacting via the pairwise spherically symmetric potential, fðrÞ. It is found that all fcc static models in which the range of interaction is only between nearest neighbour particles are placed on a universal curve in the XY plane. It is shown that auxetic behaviours can be achieved with simple static fðrÞ analytic forms. The influence of the next neighbour interactions on the universal curve is also considered. In order to assess the role of thermal fluctuations, molecular dynamic simulations for two different fðrÞ (the Lennard-Jones (LJ) and the tethered particle potentials) were performed. At low temperatures the studied systems are well represented by the universal curve and on increasing temperature a systematic departure from it is observed.

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Section: Extreme Poisson's Ratiomentioning

confidence: 92%

“…completely auxetic, according to Ting and Barnett definition 5) materials, are extremely rare in nature. However, compounds exist that apparently are in the auxetic region, including the rare earth alloys composed of sulphur with samarium, doped suitably with lanthanum, yttrium and thulium 18, 20, 21, 23.…”

Section: Extreme Poisson's Ratiomentioning

confidence: 99%

Auxeticity of cubic materials under pressure

Brańka

Heyes

Wojciechowski

2010

Physica Status Solidi (b)

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“…Another inequality s 12 > 0 ensuring the negativity of Poisson's ratio is satisfied only for a few cubic crystals in agreement with the experimental data given in Refs. . Such Poisson's ratio does not vary over the cross‐section of the tubes, so that the tubes are completely auxetics (Table ).…”

Section: From One‐layered To Two‐layered Tubesmentioning

confidence: 99%

“…Radial and angular Poisson's ratios and Young's modulus of two‐layered tubes are calculated for some cubic crystals. The experimental values of the compliance coefficients for them are taken from the reference book and articles . It is demonstrated that the anomalous behavior of the effective elastic characteristics of two‐layered tubes is possible with many combinations of nonauxetic–auxetic and some combinations of nonauxetic–nonauxetic.…”

Section: Introductionmentioning

confidence: 99%

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Two‐Layered Tubes from Cubic Crystals: Auxetic Tubes

Goldstein

Городцов

Lisovenko

et al. 2017

Physica Status Solidi (b)

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Effective Young's modulus and Poisson's ratios of two‐layered cylindrical hollow tubes made of cubic crystals (auxetics and nonauxetics) are considered. An analysis of longitudinal tension of stretching tubes is performed within the framework of curvilinear‐anisotropic elasticity and Saint‐Venant's approximation. Analytical dependences of effective Young's modulus on the compliance coefficients of the initial crystals and layer thickness as ratio of composites auxetics–nonauxetics are obtained. Deviations from the “rule of mixtures” predictions which increase with increasing Young's modulus of initial nonauxetics are demonstrated. It is found that effective Poisson's ratios of two‐layered tubes depend on the ratio of their thicknesses, the dimensionless combinations of compliance coefficients and a dimensionless radial distance. An effect of tube components on negativeness of effective Poisson's ratio of the composite auxetics–nonauxetics proved to be strongly dependent on the value of Young's modulus for nonauxetic component. It is shown that effective Poisson's ratios for some characteristics of the initial crystals and ratios of layer thicknesses may fall outside the limits on Poisson's ratios of isotropic materials. It is shown that many two‐layered tubes composed of pairs of nonauxetics can have large negative effective Poisson's ratios.

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1.2.2.5 References for 1.2.2

Suski¹,

Palewski²

Pnictides and Chalcogenides II (Lanthanide Monochalcogenides)

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Brillouin spectroscopy on doped SmS

Cited by 7 publications

References 8 publications

Auxeticity of cubic materials under pressure

Auxeticity of cubic materials under pressure

Two‐Layered Tubes from Cubic Crystals: Auxetic Tubes

1.2.2.5 References for 1.2.2

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