Structural and electronic properties of exohedrally doped neutral silicon clusters LnSin (n = 5, 10; Ln = Sm, Eu, Yb)

Abstract

Lanthanide-doped silicon clusters have been extensively studied in the fields of optoelectronics, magnetism and nanomaterials during the last decade. Herein, systematic structure searches for typical neutral clusters of lanthanide-doped silicon clusters LnSi_n (n = 5, 10; Ln = Sm, Eu, Yb) have been performed by means of density functional theory coupled with the “stochastic kicking” global search technique. It is found that the Ln atom in LnSi_n prefers to locate on the surface of Si_n to form an exohedral structure, and this exohedral configuration may dominate the nascent structure of LnSi_n. The spin density and Mulliken population analyses indicate that LnSi_n clusters possess remarkable magnetic moments (except for YbSi_n), which are mainly supplied by the Ln 4f electrons (except for Yb). Density of states visually shows the significant spin polarization for open-shell structures of SmSi_n and EuSi_n. As for the YbSi_n (n = 5, 10) system, it has a closed-shell electronic structure with a large HOMO–LUMO gap of 2.72 eV. Bonding analysis, including localized orbital locator and electron density difference, shows that the Si–Si covalent interaction and Sm–Si electrostatic interaction are important for the structural stability of LnSi_n.