Corrosion product fingerprints: the ab initio study of LiCl-CrCl3 molten salt

During molten salt reactor operation, corrosion of structural materials is inventible. Commonly, alloy corrosion pathways include a selective dissolution of chromium, leading to its embedding in the melt structure. To date, only few studies concern the issue of Cr local structure patterns in relevant molten salts. Meanwhile, it was shown that Cr promotes the formation of intermediate-range order structures, which could affect crucial properties of a melt. In this paper, a small CrCl3 additive to LiCl melt was simulated ab initio. We found that Cr exhibits preferential 6-fold coordination. The lifetime of Cr-Cl bond has a relatively long duration of 8 ps, which allows considering [CrCl6] grouping as [CrCl6]3– complex ion, with the diffusion coefficient of 1.4 · 10–9 m2/s. Calculating the vibrational properties of [CrCl6] bridges the gap between simulations and experiment by pointing out the intense IR and Raman bands, which are at 358 and 349 cm–1, respectively.