STABLE STRUCTURES, MAGNETIC AND ELECTRONIC PROPERTIES OF SMALL BIMETALLIC PtCo NANOALLOYS UP 5 ATOMS: A DFT STUDY

Abstract

In bulk regime size, Co presents an HCP phase and Pt has an FCC phase, both present interesting properties of technological relevance. Co is ferromagnetic and Pt is a good catalyst. Nanoalloying allows us to play with the size and the chemical composition to achieve new properties and functionalities that do not exist at the bulk regime. In this work, we studied the interaction between PtCo atoms and how to affect the chemical order, the magnetic properties and electronic properties of these binary nanoalloys up 5 atoms. Our results show that Co atoms prefer to be localized at sites with the highest coordination in nanoalloys with 5 atoms, in PtCo clusters with 4 atoms, we found planar geometries as the stable ones. All the nanoalloys have a favorable atom mixing; the bimetallic clusters considered in this study show magnetic behavior and present a ferromagnetic-like order where the value of the total magnetization depends on the number of Co atoms of the cluster. We have considered the vertical ionization potential to determine the donation of electrons and the capture of electrons is studied through the electronic affinity and these are related to the chemical hardness which is an index of catalytic activity. This study was done into the DFT scheme as implemented in the SIESTA code using a generalized gradient approximation.