Thermodynamic properties calculation for MgO–SiO2 liquids using both empirical and first-principles molecular simulations

Abstract

Both classical molecular dynamics simulations and first-principles molecular simulations were carried out to investigate the thermodynamic properties of MgO–SiO₂ melts at 4000 K and 0 GPa. After equilibrating both the mini-sized and large-sized systems using classical molecular dynamics simulations, several properties and structures were calculated and compared. Consistencies were found between results from mini-sized systems and those from large-sized systems. The first-principles molecular dynamics simulations were continued for 6 ps from several independent configurations output from the mini-sized systems. The enthalpy of mixing was calculated, and results were compared with those from empirical molecular simulations. We found that first-principles simulation modified the thermodynamic properties of silicate melts, and led to positive enthalpy of mixing at high SiO₂ concentrations and negative ones at low SiO₂ concentrations. Regressing data using the Margules equation led to results consistent with available references.