Puzzles of Surface Segregation in Binary Pt–Pd Nanoparticles: Molecular Dynamics and Thermodynamic Simulations

Abstract

Up till now, there have been extremely contradictory opinions and inadequate results concerning surface segregation in binary platinum–palladium (Pt–Pd) nanoparticles, including the problems regarding segregating components, as well as the size and temperature dependences of segregation. Taking into account such a situation, we investigated the surface segregation in Pt–Pd nanoparticles by combining atomistic (molecular dynamics) and thermodynamic simulations. For molecular dynamics experiments, the well-known program LAMMPS and the embedded atom method were employed. In the course of the atomistic simulations, two different sets of parameterizations for the Pt–Pt, Pd–Pd, and Pt–Pd interatomic interaction potentials were used. The thermodynamic simulation was based on solving the Butler equation by employing several successive approximations. The results obtained via atomistic simulation and thermodynamic simulation on the basis of the Butler equation were compared with each other, as well as with predictions that were based on the Langmuir–McLean equation and some experimental data. Both simulation methods (atomistic and thermodynamic) predicted the surface segregation of Pd, which diminishes with the nanoparticle size and with increasing temperature. Our simulation results do not confirm the predictions of some authors on surface segregation inversion, i.e., the reversal from the surface segregation of Pd to the surface segregation of Pt when diminishing the nanoparticle size.

Tetrahedral Clusters Stabilized by Alloying

“…Eventually, as can be seen in Figure 1 , Pt atoms in excess are located inside the hexagonal stacking fault islands. The surface segregation of palladium is consistent with previous numerical simulations 37 − 40 and experiments. 41 − 44 To our knowledge, the stability of any of these structures at the DFT level was never proven.…”

“…Eventually, as can be seen in Figure , Pt atoms in excess are located inside the hexagonal stacking fault islands. The surface segregation of palladium is consistent with previous numerical simulations − and experiments. − To our knowledge, the stability of any of these structures at the DFT level was never proven. In the following section, we derive the new series of magic numbers for these structures, referring to Figure for a schematic visualization of the proof.…”

Efficient Implementation of the Binary Common Neighbor Analysis for Platinum-Based Intermetallics

“…Atomic simulations provide detailed insights into material equilibrium structures, thermodynamic properties, and dynamic processes at the atomic scale, primarily through methods such as molecular statics, molecular dynamics (MD), and Monte Carlo (MC) simulations [1][2][3][4]. One of the most challenging aspects of atomic simulations lies in analyzing the vast amounts of generated data [3].…”