Molecular Dynamics Simulation of Viscosity of the CaO, MgO and Al2O3 Melts

Viscosity of oxide melts is a fundamental physicochemical property that plays a critical role in important technological and natural processes like slag flow, slag/metal separation, volcano eruptions etc. Unfortunately, many oxides melt at extremely high temperatures and are highly corrosive in the liquid state, which makes experimental measurement of viscosity by conventional experimental techniques a difficult, expensive, and sometimes impossible task. In this case it might be helpful to use other methods to determine viscosity, such as modelling or simulation. In the present paper the shear viscosity coefficients of the liquid CaO, MgO, and Al2O3 have been simulated via the classical molecular dynamics and compared to the available viscosity data (e.g. experimental viscosities, other model predictions) collected and stored in a databank by one of the authors. Different viscosity calculation techniques (e.g. the Green-Kubo equation, the Einstein relation, and the non-equilibrium molecular dynamics methods) coupled with MD have been employed to ensure a more reliable viscosity calculation. It has been shown that the simulated viscosities of the CaO and MgO melts are close to those calculated by phenomenological viscosity models and represent a plausible estimation for viscosity of these unary systems. It has also been shown that the simulated viscosity of the Al2O3 melt is lower than the majority of the available experimental data. In general, it has been demonstrated that the molecular dynamics simulation could provide a reasonable estimation of viscosity, especially if no other viscosity data is available.