Post-optimization elimination of inverted miscibility gaps

Among numerous thermodynamic models of various systems published in recent decades, there is a small yet not negligible portion of assessments predicting an inverted miscibility gap in the liquid phase at elevated temperatures, a gap which in reality does not exist. Two methods to eliminate such a post-optimization artifact via a computationally simple correction of the excess Gibbs energy of the melt are proposed. Both methods employ optimization under topological constraints controlling the sign of the second derivative of the molar Gibbs energy of mixing with respect to concentration. Their applicability is demonstrated on the Sn – Zr system whose thermodynamic description incorporated in the COST 507 database leads to an unintended inverted miscibility gap.