On the Mg-Pb system. Calorimetric studies and thermodynamic calculations

Highlights: • A new set of calorimetric measurements of mixing enthalpy of liquid Mg-Pb is presented. • Thermophysical properties of intermetallic compound Mg₂Pb were determined from ab-initio calculations. • Quasi-harmonic approximation was involved in ab-initio calculations. • A new thermodynamic model of Mg-Pb system is proposed. -- Abstract: In this paper, the experimentally determined integral and partial molar enthalpy of mixing of liquid Mg-Pb alloys is presented. Five separate measurements were performed at 1012 and 1014 K with the use of MHTC 96 Line Evo line drop calorimeter. The values of integral molar mixing enthalpy are characterized by negative deviations from the ideal solutions in the entire concentration range. Based on obtained results and other thermodynamic quantities available in the literature the Mg-Pb phase diagram was optimized. The calculated and experimentally obtained values of the integral molar mixing enthalpy are also compared with the Miedema model prediction of the integral molar mixing enthalpy. The formation enthalpy for the Mg₂Pb phase is computed by ab initio calculations and equals −5978 J/mol of atoms at 0 K. For the Mg₂Pb intermetallic phase, the calculated bulk isothermal and adiabatic modulus, as well as a variation of primitive cell volume and thermal expansion coefficient with the temperature, are presented. Moreover, the heat content of the Mg₂Pb intermetallic phase is shown and compared with experimental data for temperatures from 0 K to its melting temperature.