Structure and energy properties of Fe(x)-Cu(1−x) nanoparticles: Morphology and size effects

Javier Rojas, Samuel Baltazar, Rafael Gonzalez, Eduardo Bringa, and Sebastian Allende

Fe-Cu nanoparticles represent a very interesting bimetallic system because of the different properties observed respect to their pristine materials 1. Cu is a paramagnetic material with a FCC lattice structure and Fe is a ferromagnetic material with a BCC lattice structure, therefore a study of the stable configurations of the bimetallic systems may be interesting in order to develop new applications. Searching routines have been performed over two systematically generated initial structures (Janus and Core-Shell) to find the most stable configurations at different Cu concentrations and sizes. These searching routines consider several cycles of annealing and minimization, which have been performed by LAMMPS software using the embedded-atom interaction 2 with the parameters developed by Bonny et al. 3. The annealing processes have been done with a stability temperature of 950K and the energy minimization is based on the conjugate gradient and “FIRE” 4 optimization algorithms consecutively applied. As a result, different configurations have been found for the several Cu concentrations and sizes, showing that Janus structures are stable for high concentrations of Cu while Core-Shell structures are stable for low concentrations. Finally structural characterization and defect analysis are performed in the most stable configurations.

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2 Murray S. Daw and M. I. Baskes. Embedded-atom method: Derivation and application to impurities, surfaces, and other defects in metals. Physical Review B, 29(12):6443–6453, jun 1984.

3 G. Bonny, R.C. Pasianot, N. Castin, and L. Malerba. Ternary Fe–Cu–Ni many-body potential to model reactor pressure vessel steels: First validation by simulated thermal annealing. Philosophical Magazine, 89(34-36):3531–3546, dec 2009.

4 Erik Bitzek, Pekka Koskinen, Franz Gähler, Michael Moseler, and Peter Gumbsch. Structural relaxation made simple. Physical Review Letters, 97(17):170201, oct 2006.