Formulation of Temperature-Dependent Thermal Conductivity of NaF, beta-Na3AlF6, Na5Al3F14, and Molten Na3AlF6 Supported by Equilibrium Molecular Dynamics and Density Functional Theory

摘要

Numerical modeling of heat transport in the side ledge of a cryolite bath as a function of its thickness requires an accurate knowledge of the thermal transport properties of the cryolite bath as well as the solid phases constituting the Side ledge. Unfortunately, clue to experimental limitations, there is a lack of;experimental-data on this subject. The aim of this work is to predict these otherwise unknown properties. The thermal conductivity of major constituents of the side ledge in their solid state, namely: NaF, beta- Na3AlF6 and Na5Al5F14 as well as molten Na3AlF6 are formulated as a function of temperature. TO achieve this, we have performed a series of equilibrium molecular dynamics simulations (EMD) in both the NPT (isobar-isotherm) and NVT (canonical) statistical ensembles. The proposed approach is purely predictive as the ionic interaction potentials were parametrized on the basis of Density Functional Theory (DFT). The results are :then Compared to a theoretical model which has been shown to be a very good predictive ability for many ionic and ionocovalent compounds. For solid NO and liquid Na3AlF6, for which data are available, the predictions were found to be in excellent agreement with experiment.