Molecular dynamics models of binary CaO-FeO, MgO-SiO2, FeO-SiO2, CaO-SiO2 and ternary CaO-FeO-SiO2 systems were constructed at 1873 K using the Born-Mayer pair potentials. The potentials included the effective dipole-dipole interactions for Ca-Fe, Mg-Si, Fe-Si and Ca-Si pairs. Parameters of the dipole-dipole interactions were found by adjusting calculated Gibbs free energies of formation of binary CaO-FeO, FeO-SiO2, MgO-SiO2 and CaO-SiO2 systems to experimental data. The thermodynamic properties of CaO-FeO-SiO2 solutions were studied by converting several iron ions into calcium ions. The Gibbs free energy increments and ratios of activity coefficients gamma (CaO)/gamma (FeO) in the ternary system were calculated. Published by Elsevier Science B.V.