Copper diffusion rates and hopping pathways in superionic Cu2Se

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dc.contributor.authorNazrul Islam, SMKen_AU
dc.contributor.authorMayank, Pen_AU
dc.contributor.authorOuyang, Yen_AU
dc.contributor.authorChen, Jen_AU
dc.contributor.authorSagotra, AKen_AU
dc.contributor.authorLi, Men_AU
dc.contributor.authorCortie, MBen_AU
dc.contributor.authorMole, RAen_AU
dc.contributor.authorCazorla, Cen_AU
dc.contributor.authorYu, DHen_AU
dc.contributor.authorWang, XLen_AU
dc.contributor.authorRobinson, RAen_AU
dc.contributor.authorCortie, DLen_AU
dc.date.accessioned2023-11-17T03:12:23Zen_AU
dc.date.available2023-11-17T03:12:23Zen_AU
dc.date.issued2021-08-15en_AU
dc.date.statistics2023-10-26en_AU
dc.description.abstractThe ultra-low thermal conductivity of Cu2Se is well established, but so far there is no consensus on the underlying mechanism. One proposal is that the fast-ionic diffusion of copper suppresses the acoustic phonons. The diffusion coefficients reported previously, however, differ by two orders of magnitude between the various studies and it remains unclear whether the diffusion is fast enough to impact the heat-bearing phonons. Here, a two-fold approach is used to accurately re-determine the diffusion rates. Ab-initio molecular dynamics simulations, incorporating landmark analysis techniques, were closely compared with experimental quasielastic/inelastic neutron scattering. Reasonable agreement was found between these approaches, consistent with a diffusion coefficient of 3.1 ± 1.3 x 10−5 cm2.s−1 at 675 K and an activation barrier of 140 ± 60 meV. The hopping mechanism includes short 2 Å hops between tetrahedral and interstitial octahedral sites. This process forms dynamic Frenkel defects. Despite the latter processes, there is no major loss of the phonon mode intensity in the superionic state, and there is no strong correlation between the phonon spectra and the increased diffusion rates. Instead, intrinsic anharmonic phonon interactions appear to dictate the thermal conductivity above and below the superionic transition, and there is only subtle mode broadening associated with the monoclinic-cubic structural transition point, with the phonon density-of-states remaining almost constant at higher temperatures. © 2021 Acta Materialia Inc.en_AU
dc.description.sponsorshipWe thank ANSTO for providing access to PELICAN at the Australian Centre for Neutron Scattering and to the Powder Diffraction beamline at the Australian Synchrotron. High performance computation was performed on the RAIJIN and PAWSEY supercomputers within the National Computer Infrastructure. This work was partially supported by the Australian Research Council (ARC) through Discovery Projects DP210101436 (DC,DY) and DP130102956 (XLW), a DECRA project DE180100314 (DC), an ARC Professorial Future Fellowship project FT 130100778 (XLW) and a Linkage Infrastructure Equipment and Facilities (LIEF) Grant LE 120100069 (XLW).en_AU
dc.identifier.articlenumber117026en_AU
dc.identifier.citationNazrul Islam, S. M. K., Mayank, P., Ouyang, Y., Chen, J., Sagotra, A. K., Li, M., Cortie, M. B., Mole, R., Cazorla, C., Yu, D., Wang, X., Robinson, R. A., & Cortie, D. L. (2021). Copper diffusion rates and hopping pathways in superionic Cu2Se. Acta Materialia, 215, 117026. doi:10.1016/j.actamat.2021.117026en_AU
dc.identifier.issn1359-6454en_AU
dc.identifier.journaltitleActa Materialiaen_AU
dc.identifier.urihttps://apo.ansto.gov.au/handle/10238/15205en_AU
dc.identifier.volume215en_AU
dc.language.isoenen_AU
dc.publisherElsevieren_AU
dc.relation.urihttps://doi.org/10.1016/j.actamat.2021.117026en_AU
dc.subjectCopper selenidesen_AU
dc.subjectNeutron diffractionen_AU
dc.subjectMolecular dynamics methoden_AU
dc.subjectThermoelectricityen_AU
dc.subjectDiffusionen_AU
dc.subjectThermal conductivityen_AU
dc.subjectPhononsen_AU
dc.titleCopper diffusion rates and hopping pathways in superionic Cu2Seen_AU
dc.typeJournal Articleen_AU
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