Molecular dynamics simulations of the local structures and transport properties of Na2CO3 and K2CO3

Abstract

Molten alkali carbonates has been researched as one of the most promising thermal energy storage (TES) materials in Concentrating Solar Power (CSP) and received extensive attentions. Some attractive properties must be determined accurately, such as thermal conductivity, and viscosity. over a wide temperature range. However, these significant thermal and transport properties are difficult to be obtained for experiments on account of high-temperature extreme conditions. Molecular dynamics (MD) is an alternative way to predict these properties for molten salts. Systematic results including density, thermal conductivity and shear viscosity as a function of temperature from molecular dynamics simulations of molten alkali carbonates are presented in detail in this paper. Both reverse nonequilibrium molecular dynamics (RNEMD) and nonequilibrium molecular dynamics (NEMD) methods are tried for thermal conductivity and viscosity, and then the results are compared to experimental values. The temperature dependence are investigated and analyzed by correlating transport properties with local structures. The results show that the Tosi-Fumi potential predicts negative temperature dependences for both viscosity and thermal conductivity of the alkali carbonates. The simulation results are in good agreement with the experimental data available in the literature.