Iron Nanoparticles Embedded in Silica Glass: A Computational Study

摘要

We performed electronic structure calculations within density functional theory including ab initio molecular dynamic simulations of isolated Fe{sub}13 and Fe{sub}55 clusters. We observed the energy preference of icosahedral over cuboctahedral clusters for both Fe{sub}13 and Fe{sub}55. The magnetic structure is ferromagnetic for Fe{sub}13 clusters, but anti-ferromagnetic for Fe{sub}55 clusters. The isolated clusters exhibit a HOMO-LUMO gap. Subsequently, we modeled the embedding of Fe{sub}13 and Fe{sub}55 clusters in silica glass, creating several models of different size. All models show a homogeneous trend after optimization, however. For embedded clusters we observed the formation of an iron oxide interface between the cluster and the dielectric matrix. The magnetization of the embedded clusters is slightly larger than the magnetization of free clusters. The small clusters retain their electronic structure around the Fermi-level, still exhibiting a HOMO-LUMO gap, despite some major geometrical distortions of the clusters.