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Article
Monte Carlo simulations of segregation in Pt-Ni catalyst nanoparticles
Journal of Chemical Physics (2005)
  • Guofeng Wang, Materials Sciences Division, Lawrence Berkeley National Laboratory, University of California, Berkeley, CA 94720
  • M.A. Van Hove, Materials Sciences Division, Lawrence Berkeley National Laboratory, University of California, Berkeley, CA 94720
  • P.N. Ross, Materials Sciences Division, Lawrence Berkeley National Laboratory, University of California, Berkeley, CA 94720
  • M.I. Baskes, MST-8 Structure and Property Relations Group, Los Alamos National Laboratory, Los Alamos, NM 87545
Abstract
We have investigated the segregation of Pt atoms in the surfaces of Pt-Ni nanoparticles, using Modified Embedded Atom Method potentials and the Monte Carlo method. The nanoparticles are constructed with disordered fcc configurations at two fixed overall concentrations (50 at.% Pt and 75 at.% Pt). We use four kinds of nanoparticle shapes (cube, tetrahedron, octahedron, and cubo-octahedron) terminated by {111} and {100} facets to examine the extent of the Pt segregation to the nanoparticle surfaces and determine the equilibrium structures of Pt-Ni nanoparticles at T=600 K. The model particles contain between 560 and 4631 atoms (particle size ranging from 2.5 to 5 nm). Our results imply that a complete {100}-facet reconstruction could make the cubo-octahendral Pt-Ni nanoparticles most energetically favorable, consistent with experimental observations. We predict that at 600 K due to segregation the equilibrium Pt50Ni50 nanoparticles with fewer than 2000 atoms and Pt75Ni25 nanoparticles with fewer than 4000 atoms would achieve a surface-sandwich structure, in which the Pt atoms are enriched in the outermost and third atomic shells while the Ni atoms are enriched in the second atomic shell. We also find that, due to an order-disorder transition, the Pt50Ni50 cubo-octahedral nanoparticles containing more than 2000 atoms would form a core-shell structure with a Pt-enriched surface and a Pt-deficient homogenous core.
Disciplines
Publication Date
January, 2005
DOI
10.1063/1.1828033
Citation Information
Guofeng Wang, M.A. Van Hove, P.N. Ross and M.I. Baskes. "Monte Carlo simulations of segregation in Pt-Ni catalyst nanoparticles" Journal of Chemical Physics Vol. 122 Iss. 2 (2005) p. 024706-1 - 024706-12 ISSN: 10897690
Available at: http://works.bepress.com/mavanhove/72/