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The Complex Structure of Molten NaCl-CrCl3 Salt: Cr-Cl Octahedra Network and Intermediate-Range Order
preprintsubmitted on 18.09.2020, 03:13 and posted on 22.09.2020, 12:16 by Qing-Jie Li, David Sprouster, Guiqiu Zheng, Jӧrg Neuefeind, Alex Braatz, Daniel Olds, Stephen Lam, Ju Li, Boris Khaykovich, Joanna McFarlane
The resurgence of the Molten-Salt Nuclear Reactors (MSR) creates interesting problems in molten-salt chemistry. As MSRs operate, the composition and physical properties of salts change because of fission and corrosion. Since Cr is the principal corrosion product and NaCl is a common constituent, we studied the atomic structure of molten NaCl-CrCl3. We found networks of CrCl3− 6 octahedra and an intermediate-range order with nonmonotonic temperature behavior in a remarkable agreement between measurements and ab initio simulations. Even though the corrosion results in minute quantities of dissolved Cr, the speciation of Cr could lead to changes in molten-salt properties in nuclear and solar salts. In particular, we found a much lower than expected melting temperature and a broad metastable liquid-solid coexistence phase. The availability of Cr isotopes with very different neutron-scattering properties makes Cr an ideal model multi-valent ion for experimental validation of new atomistic models such as neural network interatomic potentials.