Molecular dynamics simulation of binary mixtures of molten alkali carbonates

摘要

Molecular Dynamics simulations have been performed of three binary eutectic mixtures: Li/KCO(sub 3) (62-38 mol%), Li/KCO(sub 3) (43-57 mol%) and Li/NaCO(sub 3) (53-47 mol%) at 1200K. Thermodynamic, structural and dynamical changes upon mixing the alkali carbonates have been investigated. For the thermodynamic properties no significant deviations from linear additivity were found. The short-range order in the mixtures differs in many respects from the short-range order found in the pure components. The Li(sup +) ions are coordinated by a smaller number of oxygen atoms, the Na(sup +) and K(sup +) ions by a large number. The Li(sup +) ions become trapped in their first coordination shell, leaving relatively more space for the heavier atoms. This feature is the cause of the often-observed non-additivity of the dynamic properties of these mixtures. The Chemla effect in Li/KCO(sub 3), the large negative deviations from linear additivity for the electrical conductivity, as well as the dependency of the self-diffusion of the cations on the Li(sub 2)CO(sub 3) contents, can now be understood. 11 figs., 6 tabs., 28 refs.