The thermodynamic calculation and evaluation of surface tension in ternary Na-K-Cs liquid were performed to investigate the Butler model’s applicability with various geometric factors. The Butler model is a classic model used to evaluate the surface tension of binary and ternary liquids using thermodynamic data. In this study, the thermodynamic model incorporated binary Cs-K, Cs-Na, and Na-K models and a simple interaction energy model between ternary Na, K, and Cs. The phase diagrams and the activities obtained by the thermodynamic calculation were validated with past experimental data.

Furthermore, the surface tension evaluated using the Butler model with () was comparable to the experimental data with N/m and N/m. Furthermore, we compared the K concentration dependence of the surface tension of Na-K liquids up to 600 K with that of the density function theory results. The gave us the best-estimated surface tensions in Na-K-Cs liquid.