Construction of modified embedded atom method potentials for the study of the bulk phase behaviour in binary Pt–Rh, Pt–Pd, Pd–Rh and ternary Pt–Pd–Rh alloys

• Published in: Calphad Vol. 33; no. 2; pp. 370 - 376
• Main Authors: Luyten, J., De Keyzer, J., Wollants, P., Creemers, C.
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier Ltd 01-06-2009; Elsevier
• Subjects: Cross-disciplinary physics: materials science; rheology; Exact sciences and technology; Materials science; Modified embedded-atom method; Monte Carlo simulations; Phase diagrams and microstructures developed by solidification and solid-solid phase transformations; Phase diagrams of metals and alloys; Physics; Pt–Pd–Rh; Semi-empirical interatomic potential; Ternary alloys; Ternary alloys; Pt–Pd–Rh; Semi-empirical interatomic potential; Monte Carlo simulations; Modified embedded-atom method; Platinum alloys; Theoretical study; Rhodium alloys; Binary alloys; Interatomic potential; Monte Carlo methods; Palladium alloys; Pt-Pd-Rh; Phase equilibria; Embedded atom method; Semiempirical method
• ISSN: 0364-5916; 1873-2984
• DOI: 10.1016/j.calphad.2008.10.007

A first attempt is made to simulate the solid part of the phase diagram of the ternary Pt–Pd–Rh system. To this end, Monte Carlo (MC) simulations are combined with the Modified Embedded Atom Method (MEAM) and optimised parameters entirely based on Density Functional Theory (DFT) data. This MEAM potential is first validated by calculating the heat of mixing or the demixing phase boundary for the binary subsystems Pt–Rh, Pt–Pd and Pd–Rh. For the disordered alloy systems Pt–Rh and Pt–Pd, the MC/MEAM simulation results show a slightly exothermic heat of mixing, thereby contradicting any demixing behaviour, in agreement with other theoretical results. For the Pd–Rh system the experimentally observed demixing region is very well reproduced by the MC/MEAM simulations. The extrapolation of the MEAM potentials to ternary systems is next validated by comparing DFT calculations for the energy of formation of ordered Pt–Pd–Rh compounds with the corresponding MEAM energies. Finally, the validated potential is used for the calculation of the ternary phase diagram at 600 K.