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 1 873 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 Ca 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.