Structural dynamics of Schottky and Frenkel defects in ThO2: A density-functional theory study

Samuel Moxon, Jonathan Skelton, Joshua S. Tse, Joseph Flitcroft, A. Togo, David J. Cooke, E. Lora Da Silva, Robert M. Harker, Mark T. Storr, Stephen C. Parker, Marco Molinari

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9 Citations (SciVal)

Abstract

Thorium dioxide (ThO2) is a promising alternative to mixed-oxide nuclear fuels due to its longer fuel cycle and resistance to proliferation. Understanding the thermal properties, in particular the thermal conductivity, under reactor conditions is critical to the success of any candidate fuel material. ThO2 has a higher thermal conductivity and thus a lower operating temperature than other fuel systems. However, the presence of defects in real materials directly influences the structural dynamics and physical properties, and the impact of defects on the properties of ThO2 is largely unexplored. We have employed density-functional theory calculations to study the structure and energetics of the intrinsic Schottky and Frenkel defects in ThO2 and their impact on the thermophysical properties. We identify the anion Frenkel defect to be the most stable, and we identify characteristic spectral signatures of the defects in the phonon dispersions and infrared spectra. We further employ two approximate models to assess the impact of the defects on the thermal transport and find that both types of defect are predicted significantly to reduce the thermal conductivity. The methodology we present facilitates the prediction of the thermophysical and transport properties of defective materials at an atomistic level, and should be readily transferrable to existing and in-development nuclear fuel systems. This journal is

Original languageEnglish
Pages (from-to)1861-1875
Number of pages15
JournalJournal of Materials Chemistry A
Volume10
Issue number4
Early online date7 Jan 2022
DOIs
Publication statusPublished - 28 Jan 2022

Bibliographical note

Funding Information:
SM and MM acknowledge the University of Hudderseld (UoH) EPSRC-DTP competition 2018–19 (EP/R513234/1) for funding. JMS is grateful to UK Research and Innovation (UKRI) for the award of a Future Leaders Fellowship (MR/T043121/1), and to the University of Manchester (UoM) for the previous support of a UoM Presidential Fellowship. ELdS acknowledges nancial support from the NECL project under NORTE-01-0145-FEDER-022096. Analysis was performed on the Orion computing facility at the UoH and on the Computational Shared Facility at UoM. Calculations were run on the ARCHER and ARCHER2 UK National Supercomputing Services via our membership of the UK HEC Materials Chemistry Consortium (MCC; EPSRC EP/ L000202, EP/R029431). We would also like to acknowledge computing time granted through the EU PRACE DECI-16 16DECI0044 SDAnOx project. To the extent that this paper relies on the contribution of RMH/MTS, then the copyright vests in the @British Crown Copyright 2020/AWE.

ASJC Scopus subject areas

  • Chemistry(all)
  • Renewable Energy, Sustainability and the Environment
  • Materials Science(all)

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