Thermodynamic investigation of the RbBr–TbBr3 system

The thermodynamic properties and phase diagram of the RbBr–TbBr3 system were analyzed by means of the CALPHAD method in this work. Thermodynamic models were defined in order to describe the Gibbs energies of the individual phases, and the model parameters were optimized from the experimental thermodynamic and phase diagram data. The phase diagram, the heat capacity of Rb3TbBr6 and the enthalpy of mixing of RbBr–TbBr3 liquid were calculated. The structural transitions for the Rb3TbBr6 and RbTb2Br7 compounds were also considered. Good agreement between the present calculations and the experimental data was obtained. The Gibbs energies of formation of Rb3TbBr6 and RbTb2Br7 from the pure components were predicted. A further check on the reliability of the thermodynamic modeling was provided by means of the calculated entropy of mixing of RbBr–TbBr3 liquid.