%0 Journal Article %T Temperature dependent anisotropy in the bond lengths of UO2 as a result of phonon-induced atomic correlations %+ CEA Cadarache %+ Laboratoire Structures, Propriétés et Modélisation des solides (SPMS) %+ Institut Laue-Langevin (ILL) %+ European Commission - Joint Research Centre [Karlsruhe] (JRC) %A Desgranges, Lionel %A Baldinozzi, Gianguido %A E Fischer, Henry %A Lander, Gerard, H %< avec comité de lecture %@ 0953-8984 %J Journal of Physics: Condensed Matter %I IOP Publishing %V 35 %P 10LT01 %8 2023-01-05 %D 2023 %R 10.1088/1361-648X/acaf1d %K uranium dioxide %K phonons %K neutron total scattering %K time-space correlation function %K zone boundary phonons %K anisotropy %Z Chemical Sciences/Theoretical and/or physical chemistry %Z Chemical Sciences/Cristallography %Z Chemical Sciences/Material chemistry %Z Physics [physics]/Condensed Matter [cond-mat]/Materials Science [cond-mat.mtrl-sci] %Z Physics [physics]/Condensed Matter [cond-mat]/Strongly Correlated Electrons [cond-mat.str-el]Journal articles %X Previous experiments on cubic UO2 have suggested that the temperature dependences of the nearest-neighbour U-O and U-U distances are different. We have acquired total-scattering neutron diffraction patterns out to Q = 23.5 Å−1 for 50 < T < 1023K and produced via Fourier transform a pair-distribution function PDF(r). The PDF(r) shows quite clearly that r(U-O), defined by the maximum of the U-O peak in the PDF(r), does in fact decrease with increasing temperature, whereas r(U-U) follows the lattice expansion as expected. We also observe that the r(U-O) contraction accelerates continuously above T ≈ 400 K, consistent with earlier experiments by others. Furthermore, by analysing the eigenvectors of the phonon modes, we show that the ∆5 (TO1) phonon tends to separate the eight equivalent U-O distances into six shorter and two longer distances, where the longer pair contribute to a high-r tail observed in the U-O distance distribution becoming increasingly anisotropic at higher T. These results have significance for a wide range of materials in which heavy and light atoms are combined in a simple atomic structure. %G English %2 https://cnrs.hal.science/hal-03911320/document %2 https://cnrs.hal.science/hal-03911320/file/JPCM-121137.R1.pdf %L hal-03911320 %U https://cnrs.hal.science/hal-03911320 %~ CEA %~ CNRS %~ SPMS %~ CENTRALESUPELEC %~ INC-CNRS %~ CEA-UPSAY %~ UNIV-PARIS-SACLAY %~ UNIVERSITE-PARIS-SACLAY %~ GS-CHIMIE %~ GS-PHYSIQUE %~ TEST2-HALCNRS %~ TEST3-HALCNRS