Vibrational modes and quantum zero-point energy of hydrogen in ZrH0.0155 and ZrH2

JOURNAL OF ALLOYS AND COMPOUNDS

卷:818

Article

Prisk, Timothy R.¹  Kolesnikov, Alexander, I²  Granroth, Garrett E.²  Lin, Jun-Li³  Heuser, Brent J.³ 

[1] NIST, Ctr Neutron Res, Gaithersburg, MD 20899 USA

[2] Oak Ridge Natl Lab, Neutron Scattering Div, POB 2009, Oak Ridge, TN 37831 USA

[3] Univ Illinois, Dept Nucl Plasma & Radiol Engn, Urbana, IL 61801 USA

关键词: Inelastic neutron scattering;    Anharmonic lattice dynamics;    Nuclear reactors;    Hydrides;    Transition-metal alloys;   

DOI  :  10.1016/j.jallcom.2019.152832

来源: Elsevier

【 摘 要 】

We report on an inelastic neutron scattering study of the proton dynamics in ZrH0.0155 and epsilon-ZrH2. In particular, we present measurements of the incoherent dynamic structure factor, generalized vibrational density of states, and proton momentum distribution of these two materials. Our results are generally consistent with theoretical predictions of Elsasser et al. [Mat. Res. Soc. Symp. Proc. 453 221-226 (1997)]. They argued that the effective Born-Oppenheimer potential experienced by the hydrogen atoms in epsilon-ZrH2 is nearly isotropic and harmonic at energies below 0.3 eV, but becomes anisotropic and anharmonic for higher energies. At low temperatures, the proton momentum distribution is dominated by the quantum-mechanical ground state of the protons. We find that it assumes a Gaussian shape, consistent with the concept that the potential surface is approximately harmonic for small displacements of the hydrogen atoms. However, the anharmonicity of the potential becomes readily apparent in the excited states of the hydrogen atoms, as the harmonic approximation breaks down in the description of the multiphonon bands. Published by Elsevier B.V.

【 授权许可】

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