Monte carlo simulations of segregation in Pt-Re catalyst nanoparticles
We have investigated the segregation of Pt atoms to the surfaces of Pt-Re nanoparticles using the Monte Carlo method and Modified Embedded Atom Method potentials that we have developed for Pt-Re alloys. The Pt75Re25 nanoparticles (containing from 586 to 4033 atoms) are assumed to have disordered fcc configurations and cubo-octahedral shapes (terminated by {l_brace}111{r_brace} and {l_brace}100{r_brace} facets), while the Pt50Re50 and Pt25Re75 nanoparticles (containing from 587 to 4061 atoms) are assumed to have disordered hcp configurations and truncated hexagonal bipyramidal shapes (terminated by {l_brace}0001{r_brace} and {l_brace}101 {bar 1}{r_brace} facets). We predict that due to the segregation process the equilibrium Pt-Re nanoparticles would achieve a core-shell structure, with a Pt-enriched shell surrounding a Pt-deficient core. For fcc cubo-octahedral Pt75Re25 nanoparticles, the shells consist of almost 100 at. percent of Pt atoms. Even in the shells of hcp truncated hexagonal bipyramidal Pt50Re50 nanoparticles, the concentrations of Pt atoms exceed 85 at. percent (35 at. percent higher than the overall concentration of Pt atoms in these nanoparticles). Most prominently, all Pt atoms will segregate to the surfaces in the hcp truncated hexagonal bipyramidal Pt25Re75 nanoparticles containing less than 1000 atoms. We also find that the Pt atoms segregate preferentially to the vertex sites, less to edge sites, and least to facet sites on the shell of Pt-Re nanoparticles.
- Research Organization:
- Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
- Sponsoring Organization:
- USDOE Director. Office of Science. Office of Basic Energy Sciences. Materials Science Division, Los Alamos National Laboratory Contract W-7405-ENG-36 (US)
- DOE Contract Number:
- AC03-76SF00098
- OSTI ID:
- 837932
- Report Number(s):
- LBNL-54839; R&D Project: 505705; TRN: US200507%%64
- Journal Information:
- Journal of Chemical Physics, Vol. 121, Issue 11; Other Information: Submitted to Journal of Chemical Physics: Volume 121, No.11; Journal Publication Date: 09/15/2004; PBD: 1 Apr 2004
- Country of Publication:
- United States
- Language:
- English
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