Dynamics and stability of icosahedral Fe–Pt nanoparticles

Abstract

An ab initio theoretical study on icosahedral Fe–Pt clusters – one of the most interesting nanoalloys with high application potential.

Vibrational properties and stability of FePt nanoalloys

“…The contribution from Fe vibrations in the subsurface layers or in the particle's core is slightly enhanced (about 6%), but it is notably increased by 44% in the surface shell of the Fe 42 Pt 12 particle. It is consistent with the unstable character and low melting temperatures of particles with Fe surface layers [45]. The entropy of Pt vibrations in the icosahedral NPs is very similar in the core and surface layers and it is larger by 7% comparing to the bulk.…”

“…All these calculations are performed for the ground states corresponding to T = 0 K. Thermal fluctuations may stabilize some of the considered systems, which exhibit the soft-mode behavior. Indeed, the ab initio MD studies demonstrate very high stability of the icosahedral particles with the Pt atoms in the outer shell [45]. In these simulations performed at various temperatures, the Fe 12 Pt 43 particle is very stable even at T = 1000 K and new preliminary studies indicate a very high melting temperature (around 1500 K).…”

“…The MD simulations show that the particles with the Fe atoms in the outer shell are very unstable and strongly distorted even at low temperatures [45]. It is induced by a tendency of Pt atoms to move to the surface layer even in the platinum deficient particles.…”

“…The structural order and magnetic properties of FePt nanoalloys with various morphologies were studied previously within the DFT calculations [41][42][43][44]. Recently, we have investigated the influence of chemical composition on the stability of FePt icosahedra using the ab initio molecular dynamics (MD) simulations [45].…”

Theoretical Insight into Core–Shell Preference for Bimetallic Pt-M (M = Ru, Rh, Os, and Ir) Cluster and Its Electronic Structure

“…One of the representative roles is catalysis for oxygen reduction reaction (ORR) in a proton exchange membrane fuel cell. − A lot of efforts are being made to decrease platinum (Pt) content by increasing Pt dispersion and enhancing catalytic activity. − One of typical approaches is to use core–shell structure consisting of Pt thin shell and nanoparticle core of less expensive and/or more abundant metal. − In such a bimetallic cluster/particle, physical and chemical properties of the Pt shell can be tuned by other metal at the core, leading to improvement in catalytic performance . Currently, bimetallic Pt–Ti, − Pt–Fe, , Pt–Co, , Pt–Ni, − Pt–Cu, , Pt–Ru, − and Pt–Pd ,, clusters/particles with the core–shell structure have been reported as good candidates for ORR catalyst both experimentally and theoretically. For instance, octahedral Ti 19 @Pt 60 cluster with Pt 60 shell was reported to be a highly efficient catalyst with lower Pt content for ORR, because O 2 activation and OH formation were improved by the use of Ti 19 @Pt 60 nanocluster compared to the octahedral Pt 79 cluster, where expression of “A m @B n ” (A and B = metal elements) is used hereinafter to represent a core–shell structure consisting of A m core and B n shell.…”