Molecular dynamics simulation of binary mixtures of molten alkali carbonates

Molecular dynamics simulations have been performed on three binary eutectic mixtures: Li/NaCO3 (53–47 mol%), Li/KCO3 (62–38 mol%) and KCO3 (43–57 mol%) at 1200 K. The short-range order in the mixtures differs in many respects from the short-range order found in the pure components. The Li+ ions are coordinated by a smaller number of oxygen atoms, the Na+ and K+ ions by a larger number. The Li+ ions become trapped in their first coordination shell, leaving relatively more space for the larger atoms. This feature is the cause of the often-observed non-additivity of the dynamic properties of these mixtures, such as the Chemla effect in Li/KCO3, the large negative deviations from linear additivity for the electrical conductivity, as well as the dependence of the self-diffusion coefficient of the cations on the Li2CO3 content.