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Effect of Chemical Ordering on Thermal Stability of Pt–Co Nanoparticles

Wen, Yu-Hua, Huang, Rao
Journal of physical chemistry 2019 v.123 no.18 pp. 12007-12014
alloy nanoparticles, alloys, chemical bonding, cobalt, diffusivity, heat, melting, melting point, molecular dynamics, platinum, simulation models, thermal stability
The thermal stability of metallic nanoparticles is critical for their performances and applications. In this work, we examined the thermal stability of Pt–Co nanoparticles using molecular dynamics simulations with the Gupta potentials. Disordered alloys and ordered intermetallics (L1₀ PtCo and L1₂ Pt₃Co) were modeled to investigate the influence of chemical ordering on their thermal properties. Our results show that the ordered intermetallic nanoparticles exhibit higher melting points and better thermal stability than the disordered alloy nanoparticles in spite of their identical melting mechanism. During heating, higher diffusivities of both Pt and Co are observed in the disordered alloys compared with those in the corresponding ordered intermetallics, which accelerates the development of melting. Bond analysis reveals that the number of Pt–Co bonds is remarkably larger in the ordered intermetallic nanoparticles than that in the disordered alloy nanoparticles, whereas the Pt–Pt and Co–Co bonds present the opposite trend. Both the bond length and the shape evolution exhibit diverse characteristics, depending on the chemical ordering and the lattice type.