Influence of surface ligands on the electronic structure of Fe-Pt clusters: A density functional theory study

Abstract

The geometrical and electronic structures of a chemically disordered face-centered-cubic- (fcc) FePt cluster capped with various organic ligands, including propanoic acid, propylamine, and propanethiol, were investigated by means of density functional theory (DFT) calculations within a generalized gradient approximation (GGA). Detailed analysis of the electronic structure revealed that (1) Fe atoms are the favored adsorption sites of the ligands on the surface of the FePt cluster; however, for propanethiol, adsorption can also occur at Pt sites. (2) The spin magnetic moment of Fe atoms at adsorption sites in the clusters containing adsorbed ligands decreases slightly compared to that in the bare cluster on the adsorption of the ligand, and it does not depend on the length of hydrocarbon chain of the ligand. The decrease in the magnetic moment originates from the interplay between the strong hybridization of the majority $d$ states of Fe atoms with majority $p$ states of O, N, and S atoms and the electron transfer between the ligands and Fe atoms on the surface of the clusters involving $d$, $p$, and $s$ states of the Fe atoms, as well as from the high symmetry of the surface Fe atoms on adsorption of a ligand.