Using Monte Carlo ray tracing simulations to model the quantum harmonic oscillator modes observed in uranium nitride

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DOIResolve DOI: http://doi.org/10.1103/PhysRevB.89.144302
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TypeArticle
Journal titlePhysical Review B - Condensed Matter and Materials Physics
ISSN1098-0121
Volume89
Issue14
Article number144302
Pages18; # of pages: 8
AbstractRecently an extended series of equally spaced vibrational modes was observed in uranium nitride (UN) by performing neutron spectroscopy measurements using the ARCS and SEQUOIA time-of-flight chopper spectrometers [A. A. Aczel, Nat. Commun. 3, 1124 (2012)2041-172310.1038/ncomms2117]. These modes are well described by three-dimensional isotropic quantum harmonic oscillator (QHO) behavior of the nitrogen atoms, but there are additional contributions to the scattering that complicate the measured response. In an effort to better characterize the observed neutron scattering spectrum of UN, we have performed Monte Carlo ray tracing simulations of the ARCS and SEQUOIA experiments with various sample kernels, accounting for nitrogen QHO scattering, contributions that arise from the acoustic portion of the partial phonon density of states, and multiple scattering. These simulations demonstrate that the U and N motions can be treated independently, and show that multiple scattering contributes an approximate Q-independent background to the spectrum at the oscillator mode positions. Temperature-dependent studies of the lowest few oscillator modes have also been made with SEQUOIA, and our simulations indicate that the T dependence of the scattering from these modes is strongly influenced by the uranium lattice.
Publication date
LanguageEnglish
AffiliationSecurity and Disruptive Technologies; National Research Council Canada
Peer reviewedYes
NPARC number21272715
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Record identifier92ab4201-9913-404c-9702-9e5c9e96b238
Record created2014-12-03
Record modified2016-05-09
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