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.