Energetics of melting of Yb₂O₃ and Lu₂O₃ from drop and catch calorimetry and first principles computations

The energetics of melting of Yb₂O₃ (T_fus 2707 ± 20 K) and Lu₂O₃ (T_fus 2762 ± 15 K) were studied experimentally by drop-and-catch (DnC) calorimetry and computationally by ab initio molecular dynamic (AI MD) techniques. Fusion enthalpies for Yb₂O₃ (102 ± 10) kJ∙mol⁻¹ and Lu₂O₃ (125 ± 10) kJ∙mol⁻¹ were derived from the steps in enthalpy increments from DnC experiments performed on liquid and solid samples laser heated in an argon flow. Fusion enthalpy values for Yb₂O₃ and Lu₂O₃ obtained from AI MD computations were 124 ± 2 kJ/mol and 124 ± 3 kJ/mol, respectively. High temperature heat capacity values for solid and liquid phases and volume change on melting were obtained from AI MD. Computed volume change on melting for both oxides is less than 1%, prompting an experimental investigation due to difference with prior experimental results. Experimental results indicate substantial dissolution of oxygen in liquid Lu₂O_3.