Thermodynamics and Elastic Properties of Ternary Alloys of Pd, Pt, and Rh Metals: A Molecular Dynamics Simulation Study

Zhangabay Turar, Yeşim Sarıbek, Zhangabay Turar, Arystanbek Kussainov, Rakhmetova Mairagul, Ali Çoruh

Thermodynamic and mechanical properties of multicomponent noble-metal alloys determine their performance in catalytic systems, energy-storage devices, and high-temperature structural materials. In the present work, temperature-dependent properties of four face-centered cubic ternary alloys of the Pd–Pt–Rh system with compositions Pd₁₅Pt₁₀Rh₇₅, Pd₅Pt₂₅Rh₇₀, Pd₅Pt₇₀Rh₂₅, and Pd₇₅Pt₁₅Rh₁₀ have been investigated by large-scale molecular dynamics simulations using the quantum Sutton–Chen potential. Calculations were performed for a supercell containing 1372 atoms in constant-enthalpy–constant-pressure, isothermal–isobaric, and microcanonical ensembles over a wide temperature range. It was found that the Pd₅Pt₇₀Rh₂₅ alloy exhibits the highest density, cohesive energy, and bulk modulus due to its high platinum content, which provides the strongest interatomic bonding. All studied compositions show negative enthalpy of formation, indicating thermodynamic stability; however, the Pd₇₅Pt₁₅Rh₁₀ alloy demonstrates the lowest miscibility. The heat capacity and thermal expansion coefficient calculated at 300 K are in good agreement with experimental data for pure palladium, platinum, and rhodium, confirming the validity of the chosen potential. Full sets of elastic constants and derived elastic moduli have been determined; all alloys satisfy mechanical stability criteria and exhibit ductile behavior, with Pd₅Pt₇₀Rh₂₅ being the most ductile. The results represent the first systematic molecular dynamics study of Pd–Pt–Rh ternary alloys and can be used for the design of next-generation catalytic and energy-related materials.

Molecular Dynamics, Quantum Sutton-Chen potential, ternary alloys, mechanical properties.