Theoretical insight into the unique structural stabilization mechanism in actinide-centered boride.

Area of Science:

• Materials Science
• Quantum Chemistry
• Nuclear Chemistry

Background:

• Metal-doped boron clusters are key for 3D nanomaterials.
• Understanding lanthanide (Ln) and actinide (An) chemistry is vital for nuclear fuel.
• Coordination chemistry and electronic structure of M B16 species are not fully understood.

Purpose of the Study:

• Investigate the geometries and electronic structures of M B16 (M = Sc, Ti, V, Co, Rh, Ir, Eu, and An = Th to Cm).
• Determine the relationship between atomic radius and structural motifs in these clusters.
• Elucidate the nature of bonding between actinides and boron.

Main Methods:

• Employed quantum-mechanical calculations at scalar-relativistic and spin-orbit coupling levels.
• Utilized global minimization of the UB16 potential energy surface.
• Performed detailed bonding analysis.

Main Results:

• Identified three distinct structural motifs (C2 drum-like, C8v bilayer, C5v half-cage) based on atomic radii.
• Actinide-boron interactions are primarily orbital-driven, unlike electrostatic interactions in transition metal analogues.
• Strong pi(An-B) bonding, involving 5f orbitals, stabilizes the C5v half-cage structures of PaB16 and UB16.

Conclusions:

• Atomic radius is the main factor controlling the structural preferences of M B16 clusters.
• Actinide-boron bonding exhibits significant 5f-covalent character.
• Findings provide fundamental insights for designing actinide-containing compounds and understanding nuclear fuel behavior.