Electronic and Molecular Structures of the CeB₆ Monomer

Area of Science:

• Materials Science
• Quantum Chemistry
• Solid-State Physics

Background:

• Bulk lanthanide hexaborides feature octahedral B₆^3- units.
• The electronic and molecular structure of CeB₆ is crucial for understanding its material properties.

Purpose of the Study:

• To probe the electronic and molecular structure of the CeB₆ molecular unit.
• To understand structural and electronic relaxation at edge and corner sites.
• To elucidate charge delocalization in the monomeric CeB₆ unit.

Main Methods:

• Anion photoelectron spectroscopy was employed to study the CeB₆ molecular unit.
• Density Functional Theory (DFT) calculations were performed to model molecular structures and electronic properties.

Main Results:

• Two competitive molecular structures, boat-like and teardrop, were identified for CeB₆ anion and neutral species.
• The teardrop structure, with a near-planar configuration and a B₆ ligand charge of -3, aligned best with experimental spectra.
• Ce adopts different orbital occupancies (4f superconfiguration in boat, 4f 6s in teardrop).
• Conductivity at edge and corner sites likely involves diffuse 6s orbitals/bands, differing from bulk 5d bands.

Conclusions:

• The teardrop structure is the preferred configuration for the CeB₆ molecular unit.
• The electronic structure suggests that surface conductivity differs significantly from bulk conductivity.
• The decoupled nature of the 4f electron influences the electronic states of the molecule.