Molecular Dynamics Calculation of the Isothermal Compressibilities of Molten Potassium Halides and KI–KX (X = F, Cl, Br) Binary Mixtures

Abstract—The isothermal compressibilities (χ_T) of individual potassium halides and some binary mixtures, namely, KI–KX (X = F, Cl, Br), are calculated using classical molecular dynamics simulation. The modeling of molten potassium halides using the Born–Mayer–Huggins pair potential shows good agreement between the calculated values of isothermal compressibility and the experimental data. A systematic underestimation of the calculated values is found for individual melts, with the maximum difference between the calculated and experimental values being 24% for potassium chloride. For binary KI–KX (X = F, Cl, Br) mixtures, the experimental concentration dependences of χ_T during the transition from the bromide ion to the fluoride ion are characterized by an increasing deviation from additivity. Even for a KI–KBr binary mixture, the calculated concentration dependence is shown to have a pronounced nonlinear character. The maximum differences (about 34%) between the calculated and experimental values of χ_T are observed for a binary equimolar KI–KF mixture.