Quintuple super bonding between the superatoms of metallic clusters

Area of Science:

• Quantum Chemistry
• Materials Science
• Superatomic Chemistry

Background:

• The discovery of stable compounds with Cr-Cr quintuple bonding (σ, 2π, 2δ) initiated a new area in chemistry.
• Previous mass spectrometry experiments identified magic numbers in sodium clusters, such as 26 and 30 electrons.

Purpose of the Study:

• To investigate the electronic structure and bonding in 26-electron (26e) and 30-electron (30e) clusters.
• To explore the possibility of quintuple bonding in superatomic systems and its relation to molecular bonding.

Main Methods:

• Unbiased global search was employed to determine the most stable cluster structures.
• Theoretical calculations were used to analyze electronic configurations, HOMO-LUMO energy gaps, and bonding patterns.

Main Results:

• The 26e Li₂₀Mg₃ cluster exhibits a stable double-icosahedral structure with a large HOMO-LUMO energy gap (1.44 eV).
• Quintuple super bonding, described as [8e](1D2S)⁵-(1D2S)⁵[8e], was identified between two superatomic icosahedral units in the 26e cluster.
• Similar quintuple bonding ([8e](1D2S)⁷-(1D2S)⁷[8e]) was observed in the 30e Li₁₈Mg₃Al₂ cluster.
• Analogies in molecular orbital diagrams and bonding patterns were drawn between these superatomic clusters and V₂/Re₂ molecules.

Conclusions:

• The identified quintuple super bonding in 26e and 30e clusters provides a link between the jellium model and traditional chemical bonding concepts.
• This work expands the understanding of chemical bonding by demonstrating its occurrence in superatomic systems.