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Title: Study of the microdynamics of liquid lithium and lithium-hydrogen melt by inelastic neutron scattering

Abstract

The frequency spectra of vibrations of Li atoms at temperatures of 22, 227, 397, and 557 deg. C and the lithium-hydrogen melt (98 at % {sup 7}Li, 2 at % H) at 557 deg. C have been obtained from the experimental neutron inelastic scattering data. On the basis of the frequency spectra, the temperature dependences of the mean-square displacement of Li atoms, the mean-square amplitudes of atomic vibrations, and the velocity autocorrelation function of atoms have been calculated. The speed of sound in liquid lithium has been estimated within the Debye model. The frequency spectra of lithium-hydrogen melt and solid lithium hydride are compared. A generalized frequency spectrum of vibrations of hydrogen atoms in lithium-hydrogen melt is obtained.

Authors:
; ; ; ;  [1];  [2]
  1. Leipunskii Institute of Physics and Power Engineering (Russian Federation)
  2. Russian Research Centre 'Kurchatov Institute' (Russian Federation)
Publication Date:
OSTI Identifier:
21090914
Resource Type:
Journal Article
Resource Relation:
Journal Name: Crystallography Reports; Journal Volume: 52; Journal Issue: 3; Other Information: DOI: 10.1134/S1063774507030212; Copyright (c) 2007 Nauka/Interperiodica; Article Copyright (c) 2007 Pleiades Publishing, Inc; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; HYDROGEN; INELASTIC SCATTERING; LIQUIDS; LITHIUM; LITHIUM HYDRIDES; NEUTRON DIFFRACTION; SOUND WAVES; SPECTRA; TEMPERATURE DEPENDENCE; TEMPERATURE RANGE 0273-0400 K; TEMPERATURE RANGE 0400-1000 K; VELOCITY

Citation Formats

Blagoveshchenskii, N. M., Morozov, V. A., Novikov, A. G., Pashnev, M. A., E-mail: pashma@ippe.ru, Savostin, V. V., and Shimkevich, A. L. Study of the microdynamics of liquid lithium and lithium-hydrogen melt by inelastic neutron scattering. United States: N. p., 2007. Web. doi:10.1134/S1063774507030212.
Blagoveshchenskii, N. M., Morozov, V. A., Novikov, A. G., Pashnev, M. A., E-mail: pashma@ippe.ru, Savostin, V. V., & Shimkevich, A. L. Study of the microdynamics of liquid lithium and lithium-hydrogen melt by inelastic neutron scattering. United States. doi:10.1134/S1063774507030212.
Blagoveshchenskii, N. M., Morozov, V. A., Novikov, A. G., Pashnev, M. A., E-mail: pashma@ippe.ru, Savostin, V. V., and Shimkevich, A. L. Tue . "Study of the microdynamics of liquid lithium and lithium-hydrogen melt by inelastic neutron scattering". United States. doi:10.1134/S1063774507030212.
@article{osti_21090914,
title = {Study of the microdynamics of liquid lithium and lithium-hydrogen melt by inelastic neutron scattering},
author = {Blagoveshchenskii, N. M. and Morozov, V. A. and Novikov, A. G. and Pashnev, M. A., E-mail: pashma@ippe.ru and Savostin, V. V. and Shimkevich, A. L.},
abstractNote = {The frequency spectra of vibrations of Li atoms at temperatures of 22, 227, 397, and 557 deg. C and the lithium-hydrogen melt (98 at % {sup 7}Li, 2 at % H) at 557 deg. C have been obtained from the experimental neutron inelastic scattering data. On the basis of the frequency spectra, the temperature dependences of the mean-square displacement of Li atoms, the mean-square amplitudes of atomic vibrations, and the velocity autocorrelation function of atoms have been calculated. The speed of sound in liquid lithium has been estimated within the Debye model. The frequency spectra of lithium-hydrogen melt and solid lithium hydride are compared. A generalized frequency spectrum of vibrations of hydrogen atoms in lithium-hydrogen melt is obtained.},
doi = {10.1134/S1063774507030212},
journal = {Crystallography Reports},
number = 3,
volume = 52,
place = {United States},
year = {Tue May 15 00:00:00 EDT 2007},
month = {Tue May 15 00:00:00 EDT 2007}
}
  • Solid and liquid para-hydrogen and a solid mixture of ortho- and para-hydrogen have been studied by inelastic neutron scattering at momentum transfers from 5 to 30 A/sup -1/. The observed scattering function can be interpreted in terms of scattering from independent hydrogen molecules using the impulse approximation when internal excitations of the molecules are included. Scattering peaks are observed at the recoil energy, shifted by the energy of the internal rotational transitions, and broadened by the translational motion of the molecules. The peaks can be fitted by Gaussian functions, showing that, to within the accuracy of the measurement, the translationalmore » momentum distribution of the hydrogen molecules in the condensed phases has a Gaussian form. The kinetic energy of the para-hydrogen molecules at 1 bar is 76 +- 9 K in the solid at 10 K and 63 +- 6 K in the liquid at 17 K. The kinetic energy for the ortho component in the solid ortho-para mixture is estimated to be the same as for the para solid within the experimental error, although extraction of quantitative information is more difficult because of the complicated spectra.« less
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  • Inelastic neutron scattering (INS) was used to study vibrational dynamics of the hydrogen atoms in natural trioctahedral phlogopite, K0.93Na0.03(Mg2.47Fe0.22Al0.16Fe0.04Tl0.06)[Si2.84Al1.16]O10OH1.71F0.28Cl0.01, within the 50-1000 cm-1 energy range. The INS spectra collected using direct geometry spectrometer SEQUOIA at ORNL were interpreted by means of the solid-state DFT calculations covering both normal mode analysis and molecular dynamics. To optimize the structure and to calculate the vibrational modes under harmonic approximation both a hybrid PBE0 and the AM05 functional were used, while the molecular dynamics calculations (60ps/1fs) were performed only with the computationally less-demanding AM05 functional. The main contributions to the dominant band within ~750-550more » cm-1 are symmetric and antisymmetric Mg-O-H bending modes, overlapping with the skeletal stretching and bending modes causing weaker secondary movements of H atoms of inner hydroxyl groups. Signatures of the Mg-O-H bending modes appear down to ~400 cm-1, where a region of octahedra deformation modes starts. These deformations cause just shallow movements of the hydrogen atoms and are mirrored by the modes with close vibrational energies. The region from ~330 cm-1 down to the low energy end of the spectrum portrays induced vibrations of the H atoms caused by deformation of individual polyhedra, translational vibrations of the parts of the 2:1 layer relative one to another, and librational and translational vibrations of the layer. The main difference between the INS spectrum of dioctahedral Al-muscovite and trioctahedral Mg-phlogopite is that the Mg-O-H modes are all assigned to in-plane vibrations of the respective hydrogen atoms.« less