Poisson's ratio in cryocrystals under pressure

Freǐman, Yu. A.; Grechnev, Alexei; Tretyak, S. M.; Goncharov, Alexander F.; Gregoryanz, Eugene

doi:10.1063/1.4922095

Cited by 2 publications

(4 citation statements)

References 23 publications

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“…Such anomalous PR behavior of He was often thought to be a quantum zero-point vibration (ZPV) effect, however, as we show in the present paper and in Ref. 7, this is not the case. A theoretical calculation of elastic moduli by Nabi et al 8 using den-sity functional theory (DFT) in local Airy gas (LAG), local density approximation (LDA) and generalized gradient approximation (GGA) soon followed the experiment.…”

Section: Introductioncontrasting

confidence: 49%

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Elastic anisotropy and Poisson's ratio of solid helium under pressure

et al. 2015

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The elastic moduli, elastic anisotropy coefficients, sound velocities and Poisson's ratio of hcp solid helium have been calculated using density functional theory in generalized gradient approximation (up to 30 TPa), and pair+triple semi-empirical potentials (up to 100 GPa). Zero-point vibrations have been treated in the Debye approximation assuming 4 He isotope (we exclude the quantumcrystal region at very low pressures from consideration). Both methods give a reasonable agreement with the available experimental data. Our calculations predict significant elastic anisotropy of helium (△P ≈ 1.14, △S1 ≈ 1.7, △S2 ≈ 0.93 at low pressures). Under terapascal pressures helium becomes more elastically isotropic. At the metallization point there is a sharp feature in the elastic modulus CS, which is the stiffness with respect to the isochoric change of the c/a ratio. This is connected with the previously obtained sharp minimum of the c/a ratio at the metallization point.Our calculations confirm the previously measured decrease of the Poisson's ratio with increasing pressure. This is not a quantum effect, as the same sign of the pressure effect was obtained when we disregarded zero-point vibrations. At TPa pressures Poisson's ratio reaches the value of 0.31 at the theoretical metallization point (V mol = 0.228 cm 3 /mol, p = 17.48 TPa) and 0.29 at 30 TPa. For p = 0 we predict a Poisson's ratio of 0.38 which is in excellent agreement with the low-p-low-T experimental data.

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Section: Introductioncontrasting

confidence: 49%

“…This behavior of σ is highly unusual, although solid hydrogen 6,7 also has negative dσ/dp at least for low pressures. All heavier rare-gas solids (RGSs) 7 have positive dσ/dp. The difference in behavior between He and heavier RGSs is, we repeat, is not a quantum effect, i.e.…”

Section: Poisson's Ratiomentioning

confidence: 99%

Elastic anisotropy and Poisson's ratio of solid helium under pressure

et al. 2015

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“…Third, we used exactly the parametrization of pair and three-body forces as previously done in Refs. 31,[43][44][45][46] . Specifically, the pair potential (energy of a pair of H 2 molecules) is…”

Section: B Theorymentioning

confidence: 99%

“…From a theoretical point of view, it has been demonstrated 30 that PR decreases monotonously for hcp helium in agreement with the experiment 28 , reaching the value of 0.29 at 30 TPa. For hcp hydrogen in phase I it has been estimated 31 , based on the behavior of the elastic constant C 44 , that σ also decreases with pressure but no calculation of all five independent elastic constants C ij has been performed until now.…”

Section: Introductionmentioning

confidence: 99%

Elasticity and Poisson's ratio of hexagonal close-packed hydrogen at high pressures

et al. 2017

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International audienceThe elasticity at high pressure of solid hydrogen in hexagonal close-packed (hcp) phase I has been examined experimentally by laser acoustics technique in a diamond anvil cell, up to 55 GPa at 296 K, and theoretically using pair and three-body semiempirical potentials, up to 160 GPa. In the experiments on H2 and D2, the compressional sound velocity has been measured; the Poisson's ratio has been determined by combining these data with the previously reported equation of state. At room temperature, the difference between the adiabatic and isothermal processes vanishes above 25 GPa but cannot be neglected at lower pressure. Theoretically, all five elastic constants of hcp hydrogen have been calculated, and various derived elastic quantities are presented. The elastic anisotropy of hcp hydrogen was found to be significant, with ΔP ≈ 1.2, ΔS1 ≈ 1.7, and ΔS2 ≈ 1. Calculations suggest the Poisson's ratio to decrease with pressure reaching a minimum value of 0.28 at 145 GPa. In the experiment, the Poisson's ratio is also found to decrease with pressure. Theoretical calculations show that the inclusion of zero-point vibrations on the elastic properties of H2 does not result in any drastic changes of the behavior of the elastic quantities

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Poisson's ratio in cryocrystals under pressure

Cited by 2 publications

References 23 publications

Elastic anisotropy and Poisson's ratio of solid helium under pressure

Elastic anisotropy and Poisson's ratio of solid helium under pressure

Elasticity and Poisson's ratio of hexagonal close-packed hydrogen at high pressures

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