Molecular Dynamics Simulation of Dilute Solutions of MeO and MeF₂ in the CaO–CaF₂ System

Abstract

Models of oxide–fluorides CaO–CaF₂ with additions of MeO and MeF₂ were constructed and investigated by molecular dynamics method at 1873 K. It was found out that the CaO–CaF₂ system is close to the ideal solution. Structure of oxide–fluorides is topologically dense, total coordination number for Ca²⁺ ions changes from 5.2 to 6.8. The Ca–Me–O–F system (Me=Mg, Fe, Sr and Ba) was simulated by replacement of a few Ca²⁺ ions by the same number of Me²⁺ ions. Activity coefficients of MeO and MeF₂ solutes in the CaO–CaF₂ system were calculated and discussed in terms of basicity (acidity) of the solution. Analysis of MeO and MeF₂ activity coefficients in the CaO–CaF₂ system showed that with respect to MeO oxides, the CaO–CaF₂ system could be considered as a basic solution for CaO mole fraction above 0.8–0.9. At lower CaO concentration the CaO–CaF₂ system behaves as an acidic solution. With respect to MeF₂ solutes, the CaO–CaF₂ system may be regarded as a basic solution at about all compositions except the vicinity of pure CaF₂.