Supported Bimetallic Pt-Au vs Intermetallic Ni-Al Nanoparticles: Structural Features Predicted by Molecular Dynamics Simulations
Matluck Afolabi
Department of Chemical and Biomolecular Engineering, University of Tennessee
Surface composition in binary and multicomponent systems is of fundamental importance in heterogeneous catalysis, as catalytic activity and selectivity are strongly governed by the atomic arrangement at the surface. Experimental studies have shown that bimetallic nanoparticles frequently undergo thermally induced surface segregation and restructuring under elevated temperature conditions, resulting in core-shell morphologies and parent transition metal (TM)-like or chemically inhomogeneous surface compositions. In contrast, intermetallic compounds (IMCs) often preserve well-defined stoichiometric ordering and chemically homogeneous surfaces due to their intrinsically ordered crystal structures. In this study, molecular dynamics (MD) simulations were employed to investigate chemical ordering, atomic segregation, and surface reconstruction under varying thermodynamic environments.
Platinum-gold (Pt-Au) bimetallic systems and nickel-aluminum (Ni-Al) intermetallic compounds were examined over a range of stoichiometries, temperatures, hydrogen chemical potentials, and support conditions. Radial distribution function (RDF) analysis was used to evaluate atomic segregation behavior and chemical ordering within nanoparticle clusters. The results demonstrate a strong tendency for Pt-Au nanoparticles to form core-shell structures, driven by favorable Pt-Pt interactions relative to Pt-Au and Au-Au interactions, resulting in Pt enrichment within the nanoparticle core and Au segregation toward the surface. Overall, weak electronic interaction in the Pt-Au system facilitated deficient bulk chemical ordering resulting in pronounced surface compositional heterogeneity1.
In contrast, Ni-Al intermetallic systems display substantially reduced surface-bulk segregation, yielding surface compositions that closely reflect bulk stoichiometry. Specifically, NiAl and Ni3Al exhibit pronounced short-to medium-range chemical ordering analogous to the B2 and L12 crystal structures, respectively and is a direct function of strong covalent bond interaction between Ni-Al systems. Collectively, these findings suggest that electronic structure and bonding characteristics fundamentally govern atomic ordering behavior and play a critical role in the rational design of stable and selective catalytic materials.2
Interactive Structures
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References
1. Brian H. Morrow and Alberto Striolo (2010) Supported bimetallic Pt-Au nanoparticles: Structural features predicted by molecular dynamics simulations. Physical Review B, 81: 155437. doi: 10.1103/PhysRevB.81.155437.
2. Lifang Sun et al. (2024),Local chemical order enables an ultrastrong and ductile high-entropy alloy in a cryogenic environment. Sci. Adv.10, eadq6398. doi: 10.1126/sciadv.adq6398.
posted: May 2026.
updated: May 2026.