Pair distribution function analysis for Pt-Pd-Co atomic mobility in nanoparticles

Through the in-situ monitoring of fuel cells in oxidation-reduction processes with ternary nanoparticles (Pt-Pd-Co), the Pair Distribution Function (PDF) is created by the Fourier transform of the high-energy X-ray diffraction pattern of the sample. Lattice deformations in nanostructures have been shown to be reflected in the oscillation of the peaks of the atomic PDF. Analyses have revealed that there is atomic mobility within the nanoparticles. Thus, in this work we study the effect on PDF of different internal variables for nanoparticles modeled based on data from a previous interdisciplinary study by a third party, the variables include temperature, vacancies and atomic species distribution. Several atomic structural models were created, and molecular dynamics simulations were applied to them using LAMMPS and the Modified Embedded Atom Method (MEAM) for the atomic interaction. The PDF’s generated from the models were compared to experimental data and the best match was identified. It is shown that a non-uniform distribution of the elements of the ternary system within the structures is the cause of the lattice strain oscillations for the nanostructures, mainly the radial distribution of Co turns out to have a greater effect on the peaks of interest in the PDF altering the general structure of the nanoparticles.