Molecular dynamics simulations of radiation response of LiAlO₂ and LiAl₅O₈

A Roy and DJ Senor and AM Casella and R Devanathan, JOURNAL OF NUCLEAR MATERIALS, 576, 154280 (2023).

DOI: 10.1016/j.jnucmat.2023.154280

We report the findings of a computational investigation of defect production and migration in two lithium aluminate ceramics: LiAlO2 and LiAl5O8. Although the first ceramic, LiAlO2 has been widely investigated computationally, especially via molecular dynamics (MD), there have been no MD studies done on LiAl5O8 up to date, due to the lack of interatomic potentials for this system. This work implemented an existing set of Li- Al-O coulombic and Buckingham potential parameters for the LiAl5O8 system from the literature, followed by validating it based on experimental values of density, crystallinity, bond lengths and melting point. The Li+ diffusion in the two ceramics was examined and was found to be one order of magnitude slower in LiAl5O8 (D0 = 3.17 x 10 -11 m2/s) as compared to that in LiAlO2 (D0 = 4.02 x 10 -10 m2/s) at 600 K. The lithium vacancy migration barrier of 4.15 eV in LiAl5O8 was more than three times that in LiAlO2 (1.31 eV) possibly due to stronger ordering in the Li-O6 octahedra of LiAl5O8 than in Li-O4 tetrahedra of LiAlO2. The Li displacement threshold energy (Ed) in LiAl5O8 was found to have a median value of 68 eV which is much higher than that in LiAlO2 (40 eV). The greater Ed for Li signifies a lower likelihood for defect formation and clustering and thus lower tendency for amorphization in LiAl5O8. The presented results show the difference in defect dynamics in the two ceramics that may help us understand the susceptibility of the two ceramics to amorphization caused by irradiation.(c) 2023 Published by Elsevier B.V.

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