Finite-Temperature Mechanical Properties of fcc-Disordered PtRh Alloys from First-Principles Calculations

First-principles calculations were performed to predict the temperature-dependent elastic properties of fcc-disordered Pt–Rh alloys over a range of compositions. Special quasirandom structures (SQSs) were employed to represent the atomic disorder in the fcc solid-solution phase. The vibrational contribution to the free energy was evaluated using the phonon quasi-harmonic approximation, enabling the calculation of finite-temperature free energies and coefficients of thermal expansion for the fcc-disordered Pt–Rh alloys. The elastic stiffness constants at different compositions were determined using the energy–strain method. By combining the calculated thermal expansion coefficients with elastic stiffness data obtained at various volumes, the temperature-dependent elastic stiffness constants of the fcc-disordered Pt–Rh alloys were determined.