Search

To develop a potential salt in a solar power generation system, some important properties must be determined, such as thermal conductivity, viscosity etc. over the entire operating temperature range. However, due to high-temperature extreme conditions, these thermal and transport properties are hard to be obtained for experiments. It is required to find an alternative way to predict these properties accurately for molten salts. Systematic results including density, shear viscosity and thermal conductivity as a function of temperature from molecular dynamics simulations of molten alkali carbonates are presented in detail in this paper. Of which, thermal conductivity and viscosity are computed from reserve nonequilibirum molecular dynamics methods. The effects of temperature have been investigated and analyzed. 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 agreement with the experimental data available in the literature. [ABSTRACT FROM AUTHOR]

Lollingite (FeAs 2 ) is considered an arsenic-bearing mineral that is oxidized faster than arsenopyrite. The geometric configuration, chemical valence bond, and microscopic reaction of the oxidation on the surface of lollingite were systematically studied, which are of great significance for understanding the mechanism of oxidative dissolution. X-ray photoelectron spectroscopy (XPS) measurements and density functional theory (DFT) calculations were carried out to characterize the (101) surface oxidation process of lollingite under the O 2 /O 2 + H 2 O conditions. XPS results confirmed that the participation of water molecules can promote the formation of abundant OH structures on the surface of lollingite, while the relative concentration of O, As(III), and Fe(III) increased. Moreover, the DFT results demonstrated that the (101) As-terminal plane of FeAs 2 was the most stable surface with the lowest surface energy. H 2 O molecules were physically adsorbed onto the Fe atoms of the lollingite surface, while oxygen molecules can readily be adsorbed on the Fe-As 2 site by chemical adsorption processes. The oxidation process of the lollingite surface with water includes the following mechanisms: adsorption, dissociation, formation of the hydrogen bond, and desorption. The dissociation of the H 2 O molecule into OH and H led to the hydroxylation of both Fe and As atoms and the formation of hydrogen bonding. The participation of H 2 O molecules can also reduce the reaction energy barrier and accelerate the oxidation reaction of the lollingite surface, especially as far as the water dissociation and formation of hydrogen bonds are concerned. According to PDOS data, there is considerable hybridization between the d orbitals of bonded Fe atoms and the p orbitals of O atoms, as well as between the p orbitals of bonded As atoms and the p orbitals of O atoms. Due to a strong propensity for orbital hybridization and bonding between the s orbitals of the H atoms in H 2 O molecules and the p orbitals of the O atoms on the (101) surface, water molecules have the ability to speed up the oxidation on the surface.