Phonon Modal Analysis of Thermal Transport in ThO2 with Point Defects using Equilibrium Molecular Dynamics
arxiv(2024)
摘要
In this study, we investigate how point defects in ThO2, an advanced nuclear
fuel as well as a surrogate for other fluorite structured materials, affect
phonon mode-resolved thermal transport based on extensive equilibrium molecular
dynamics. By incorporating the normal modes from lattice dynamics, we decompose
the trajectory and heat flux to normal mode space and extract key phonon
properties, including phonon relaxation times and their contributions to
thermal conductivity. Two types of theories are applied: one obtains phonon
relaxation times and spectral conductivity via the Boltzmann transport equation
and normal mode analysis, while the other applies the Green-Kubo theory for
modal analysis. Both approaches enable us to evaluate the effects of four types
of point defects. The strongest impact to a reduction in thermal conductivity
is from Th interstitial, followed by Th vacancy, and O defects of similar
magnitude, consistent with previous theoretical calculations.
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