On the stability of "non-magic" endohedrally doped Si clusters: A first-principles sampling study of MSi16^+ (M =Ti,V,Cr)

TL;DR

This study uses density-functional theory to analyze the stability of Si16^+ clusters doped with transition metals Ti, V, or Cr, revealing that flexible metal-Si bonding stabilizes non-magic endohedral cages.

Contribution

It demonstrates that non-magic metal-doped Si16^+ clusters can form stable endohedral cages due to adaptable hybridized bonding, expanding potential materials for cluster-assembled applications.

Findings

All three doped clusters favor a Frank-Kasper polyhedron geometry.

VSi16^+ achieves electronic shell closure, unlike TiSi16^+ and CrSi16^+.

Flexible metal-Si bonding stabilizes non-magic cage structures.

Abstract

Density-functional theory is used to study the geometric and electronic structure of cationic Si16^+ clusters with a Ti, V or Cr dopant atom. Through unbiased global geometry optimization based on the basin-hopping approach we confirm that a Frank- Kasper polyhedron with the metal atom at the center represents the ground-state isomer for all three systems. The endohedral cage geometry is thus stabilized even though only VSi16^+ achieves electronic shell closure within the prevalent spherical potential model. Our analysis of the electronic structure traces this diminished role of shell closure for the stabilization back to the adaptive capability of the metal- Si bonding, which is more the result of a complex hybridization than the orginally proposed mere formal charge transfer. The resulting flexibility of the metal-Si bond can help to stabilize also "non-magic" cage-dopant combinations, which suggests that a wider range of materials may eventually be cast into this useful geometry for cluster-assembled materials.