Mechanisms of tritium diffusion in Li2O: quantum-chemical simulation

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Abstract
Using the intermediate neglect of differential overlap MO LCAO calculation procedure and the embedded molecular cluster model the authors have investigated atomic and electronic structure and key stages of diffusive transfer of T+ and T0 in Li2O, containing cation vacancies and F+ centres. The activation energy for the cation vacancy diffusion in Li2O is calculated to be 0.33 eV. Comparing different models of T+ and T0 atomic structures and the mechanisms of their diffusion, the authors have shown that the lowest activation energy (+ ion in the cation site to transfer by a vacancy mechanism. However, the T0 diffusion activation energy is generally only slightly higher: if it occupies an interstitial position, it may jump via interstitial sites within an activation energy of about 1 eV; if it is trapped in the cation site, exchange with a nearest lattice cation will require an activation energy of about 1.1 eV. By analysing the driving forces for tritium diffusion the authors conclude that the isotopic effect cannot affect the results of their calculations.

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