Thermodynamic study of bulk and surface properties of Pb − Tl and In − Tl liquid alloys

Abstract In this study, the bulk and surface properties of Pb $$-$$ Tl and In $$-$$ Tl liquid alloys are investigated at 773 K and 723 K, respectively. Because these properties are difficult and expensive to determine experimentally at high temperatures, theoretical models are employed. For each alloy, the self-association model (SAM) is first used to obtain good agreement between the computed and experimental values of thermodynamic properties, such as the Gibbs free energy of mixing ( G M ), the entropy of mixing ( S M ), the heat of mixing ( H M ) and chemical activity. Subsequently, other properties are calculated using Darken’s diffusion equation, a semi-empirical model (Moelwyn-Hughes model) and a statistical mechanical method based on the concept of a layered structure near the interface. The results show the existence of weak hetero-coordination and weak homo-coordination in the bulk of Pb $$-$$ Tl and In $$-$$ Tl alloys, respectively. Also, more thallium atoms are present at the surface of In $$-$$ Tl alloy compared to Pb $$-$$ Tl alloy. Pb $$-$$ Tl alloy exhibits a tendency to ideal mixing at the surface, while In $$-$$ Tl alloy exhibits homo-coordination at the surface for all bulk concentrations of thallium.