Simulation of Intrinsic Defects and Cd Site Occupation in LaIn₃ and LuIn₃

Abstract:

In previous work, perturbed angular correlation spectroscopy (PAC) was used to determine jump rates of ¹¹¹Cd, the daughter of the ¹¹¹In radiotracer, in the series of phases RIn₃ (R = rare-earth element) through nuclear quadrupole relaxation. Greater relaxation, indicating faster Cd jump rates, was observed in heavy rare-earths for compositions more deficient in indium, as would be expected for diffusion mediated by vacancies on the In sublattice. On the other hand, greater relaxation was observed for light rare-earths (R = La, Ce, and Pr) for compositions with excess indium, suggesting Cd diffusion is mediated there by a different mechanism. In this work, computer simulations were carried out to better understand the nature of the relaxation observed for the light rare-earths and the origin of the change in behavior across the rare-earth series. As a first step, formation enthalpies of intrinsic defects were calculated using density functional theory (DFT) for series end-members LaIn₃ and LuIn₃. Both compounds were found to exhibit Schottky thermal disorder. Additional DFT simulations show that the binding enthalpy between In-and R-vacancies is larger in LaIn₃ than in LuIn₃, suggesting that diffusion in LaIn₃ might be mediated by divacancies. Site enthalpies of Cd also were calculated, and it was found more favorable energetically for Cd to occupy the In sublattice than the R sublattice in both end-member phases.

• Periodical: Diffusion Foundations (Volume 27)
• Pages: 40-49
• DOI: https://doi.org/10.4028/www.scientific.net/DF.27.40
• Online since: May 2020
• Authors: Matthew O. Zacate*, John P. Bevington, Gary Scott Collins
• Keywords: Cu₃Au Crystal Structure, Defect Association Enthalpy, Defect Formation Enthalpy, Diffusion Mechanism, L1 ₂ Crystal Structure, Solute Site Occupation

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