Microscopic approach to the bcc phase of solid<sup>4</sup>He

Rota, Riccardo; Boronat, J.

doi:10.1080/00268976.2011.620025

Cited by 5 publications

(5 citation statements)

References 26 publications

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“…It is worth noting that a recent QMC calculation of the Lindemann ratio for bcc 4 He including quantum-mechanical exchanges (Ref. 39) yielded a result consistent with the one reported here, lending some validation to the hypothesis that exchanges are indeed negligible. The microscopic model affords generally satisfactory to excellent agreement with measured thermodynamic properties (e.g., the pressure).…”

Section: Discussionsupporting

confidence: 71%

Atomic displacements in quantum crystals

Dusseault

2017

Phys. Rev. B

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Displacements of atoms and molecules away from lattice sites in helium and parahydrogen solids at low temperature have been studied by means of Quantum Monte Carlo simulations. In the bcc phases of 3 He and 4 He, atomic displacements are largely quantum-mechanical in character, even at melting. The computed Lindemann ratio at melting is found to be in good agreement with experimental results for 4 He. Unlike the case of helium, in solid parahydrogen there exists near melting a significant thermal contribution to molecular vibrations, accounting for roughly half of the total effect. Although the Lindemann ratio at melting is in quantitative agreement with experiment, computed molecular mean square fluctuations feature a clear temperature dependence, in disagreement with recent experimental observations.

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Section: Discussionsupporting

confidence: 71%

Atomic displacements in quantum crystals

Dusseault

2017

Phys. Rev. B

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“…The coexistence between the hcp and bcc phases of solid 4 He at fixed pressure was studied by Rota and Boronat [91] using PIMC simulations. They reported microscopic results for the energetic and structural properties of both phases.…”

Section: Heliummentioning

confidence: 99%

Path-integral simulation of solids

Herrero

Ramı́rez

2014

J. Phys.: Condens. Matter

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The path-integral formulation of the statistical mechanics of quantum many-body systems is described, with the purpose of introducing practical techniques for the simulation of solids. Monte Carlo and molecular dynamics methods for distinguishable quantum particles are presented, with particular attention to the isothermal-isobaric ensemble. Applications of these computational techniques to different types of solids are reviewed, including noble-gas solids (helium and heavier elements), group-IV materials (diamond and elemental semiconductors), and molecular solids (with emphasis on hydrogen and ice). Structural, vibrational, and thermodynamic properties of these materials are discussed. Applications also include point defects in solids (structure and diffusion), as well as nuclear quantum effects in solid surfaces and adsorbates. Different phenomena are discussed, as solid-to-solid and orientational phase transitions, rates of quantum processes, classical-to-quantum crossover, and various finite-temperature anharmonic effects (thermal expansion, isotopic effects, electron-phonon interactions). Nuclear quantum effects are most remarkable in the presence of light atoms, so that especial emphasis is laid on solids containing hydrogen as a constituent element or as an impurity.

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“…The increase of width with pressure is reproduced by Monte Carlo calculation. 43 . We also note that the width increases with temperature.…”

Section: B Momentum Distributionmentioning

confidence: 99%

Atomic momentum distribution and Bose-Einstein condensation in liquid4He under pressure

et al. 2011

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Neutron scattering measurements of the dynamic structure factor, S(Q, ω), of liquid 4 He as a function of pressure at high momentum transfer, Q, are presented. At high Q the dynamics of single atoms in the liquid is observed. From S(Q, ω) the atomic momentum distribution, n(k), the Bose-Einstein condensate fraction, n0, and the Final State broadening function are obtained. The shape of n(k) differs from a classical, Maxwell-Boltzmann distribution with higher occupation of low momentum states in the quantum liquid. The width of n(k) and the atomic kinetic energy, K , increase with pressure but the shape of n(k) remains approximately independent of pressure. The present observed and Monte Carlo calculations of K agree within error. The condensate fraction decreases from n0 = 7.25 ± 0.75% at SVP (p ≃ 0) to n0 = 3.2 ± 0.75% at pressure p = 24 bar, a density dependence that is again reproduced by MC calculations within observed error. The Final State function is the contribution to S(Q, ω) arising from the interaction of the struck atom with its neighbors following the scattering. The FS function broadens with increasing pressure reflecting the increased importance of FS effects at higher pressure.

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Microscopic approach to the bcc phase of solid⁴He

Cited by 5 publications

References 26 publications

Atomic displacements in quantum crystals

Atomic displacements in quantum crystals

Path-integral simulation of solids

Atomic momentum distribution and Bose-Einstein condensation in liquid4He under pressure

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Microscopic approach to the bcc phase of solid4He

Cited by 5 publications

References 26 publications

Atomic displacements in quantum crystals

Atomic displacements in quantum crystals

Path-integral simulation of solids

Atomic momentum distribution and Bose-Einstein condensation in liquid4He under pressure

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Product

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Microscopic approach to the bcc phase of solid⁴He