Abstract
The structural, magnetic, and thermodynamic properties of the Au(001)/Fe(001) interface are investigated as a function of the in-plane strain using density functional theory calculations for two different Au slab thicknesses: 2 and 8 monolayers. The structural and magnetic properties are analyzed by studying the interlayer distance in the direction perpendicular to the interface and the atomic magnetic moments of Fe atoms, as a function of the in-plane strain. The structural study evidences both the bulk elastic and surface and interface contributions. The atomic magnetic moments of Fe atoms are essentially dependent on their local environment (number and distance of the Fe first neighbors). Thermodynamic properties of the interface are investigated through the calculation of the interface energy and interface stress. These thermodynamic quantities are subsequently used in a simple model to evaluate the strain state of an ideal spherical symmetric Fe@Au core-shell nanoparticle. The surface elastic effects are found to be significant for nanoparticles of diameter smaller than $\ensuremath{\sim}20$ nm and predominant for diameters smaller than $\ensuremath{\sim}2.3$ nm. Interface elastic effects are weaker than surface elastic effects but can not be neglected for very small nanoparticles ($\ensuremath{\lesssim}1.9$ nm) or for thin shells.
Highlights
Targeted functionalization of nanoparticles is one of the current major challenges for applications as diverse as optics, catalysis, and biomedicine [1]
Using first-principles calculations based on density functional theory (DFT), we have investigated the structural, magnetic, and thermodynamic properties of the Au(001)/Fe(001) interface subject to an in-plane strain for two Au slab thicknesses: 2 and 8 ML
Our calculations show that the interlayer distance at the interface Au(001)/Fe(001) decreases with the in-plane strain, suggesting a tendency for (001)Au to bind more strongly to (001)Fe when the Fe slab is in tension
Summary
Targeted functionalization of nanoparticles is one of the current major challenges for applications as diverse as optics, catalysis, and biomedicine [1]. The emergence of a particular faceted morphology for a bimetallic nanoparticle is still very poorly understood It depends on many factors which come into play, including the surface and interfacial energies, the elastic energies, the chemical potentials, etc. We investigate the properties of the interface between a gold layer and an iron substrate, encountered in core-shell Fe@Au nanoparticles that were recently grown on a UHV magnetron sputtering setup [7,8]. Such nanoparticles are potentially interesting for applications since they combine some of the Fe and Au properties. IV presents a simple model used to evaluate the effects of the surface and interface stresses on the strained state of the Fe@Au nanoparticle
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