Abstract
Experimental phonon densities of states of UO2 have been deduced from double-differential neutron scattering data measured at 300 K, 600 K and 900 K using the IN6 time-of-flight spectrometer of the Institute Laue-langevin (ILL). The comparison with ab intio phonon spectra obtained at the North Caroline South University from first-principle calculations confirms that harmonic vibrations of the atoms cannot accurately reproduce the phonon broadening related to the oxygen atoms.
Highlights
The slow-neutron scattering properties of uranium dioxide (UO2) has been the subject of many experimental and theoretical studies since the pioneer works reported in the sixties [1, 2]
Major results about the acoustic and optical vibration modes of UO2 were published in a series of symposia on neutron scattering and neutron thermalization organized by the International Atomic Energy Agency, between 1960 and 1977 [3, 4]
Despite major experimental and theoretical improvements, Pang [6, 7] recently shows that first-principles phonon density of states (PDOS) simulations cannot accurately reproduce inelastic neutron scattering measurements for UO2, carried out at 295 K and 1200 K using the ARCS spectrometer of the Spallation Neutron Source (SNS)
Summary
The slow-neutron scattering properties of uranium dioxide (UO2) has been the subject of many experimental and theoretical studies since the pioneer works reported in the sixties [1, 2]. Crystal dynamics properties of UO2 have been well described by Dolling using dispersion curves measured at the triple-axis-crystal spectrometer at Chalk River [5]. Despite major experimental and theoretical improvements, Pang [6, 7] recently shows that first-principles phonon density of states (PDOS) simulations cannot accurately reproduce inelastic neutron scattering measurements for UO2, carried out at 295 K and 1200 K using the ARCS spectrometer of the Spallation Neutron Source (SNS). The present work aims to complement the work of Pang by providing experimental phonon densities of states for UO2 from room temperature to 900 K in order to stimulate theoretical studies for improving comparison to experiment
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