Multi-Doping of Si Cages: High Spin States beyond the Single-Dopant Septet Limit

TL;DR

This study uses density-functional theory to explore multi-doping of silicon cages, demonstrating the potential to achieve high spin states beyond single dopant limits, which could lead to new magneto-optic materials.

Contribution

It systematically investigates multi-doping in silicon clusters, revealing structures that sustain high spin states beyond the single-atom dopant septet limit.

Findings

Si24H24 cage supports multi-doping with high spin states.

Cr2+ doped Si24H24 exceeds single-atom septet limit.

Multiple dopants in Si28H28 achieve 18 unpaired electrons.

Abstract

Density-functional theory based global geometry optimization is employed to systematically scrutinize the possibility of multi-doping of hydrogenated Si clusters in order to achieve high spin states beyond the septet limit of a single-atom dopant. While our unbiased configurational search reveals that the previously suggested Si18H12 double hexagonal prism structure is generally too small to accommodate two dopants in magnetized state, the larger Si24H24 cage turns out to be suitable for such applications. For dimer dopants M2+ = Cr2+, Mn2+ and CrMn+, the structural integrity of the host cage is conserved in the ground-state structure of corresponding M2+@Si24H24 aggregates, as is the unusually high spin state of the guest dopant, which in case of Cr2+ already exceeds the single-atom dopant septet limit by almost a factor of two. Moreover, the possibility of further increasing the cluster spin moment by encapsulating an even larger number of dopants into a suitably sized hydrogenated Si cage is illustrated for the example of a (CrMn+)2@Si28H28 aggregate with a total number of 18 unpaired electrons. These results strongly suggest multi-doping of Si clusters as a viable route to novel cluster-based materials for magneto-optic applications.