A Systematic Theoretical Study of UC₆: Structure, Bonding Nature, and Spectroscopy

Area of Science:

• Computational Chemistry
• Materials Science
• Nuclear Engineering

Background:

• Uranium carbides are gaining interest as potential fuels for advanced nuclear reactors.
• Understanding the fundamental properties of uranium carbide clusters is crucial for their application.

Purpose of the Study:

• To determine the stable isomers of the uranium hexacarbonyl (UC6) cluster.
• To investigate the electronic structure and bonding characteristics of UC6 isomers.
• To simulate spectroscopic data for experimental identification of UC6 isomers.

Main Methods:

• Density Functional Theory (DFT) and ab initio calculations were employed.
• Scalar relativistic core potential (SC-RECP) and all-electron basis sets (ZORA-SARC) were used for uranium.
• Coupled Cluster Single Double with Perturbation Theory (CCSD(T)) was utilized for energy comparisons.
• Topological analysis of electron density investigated U-C bond nature.
• Infrared (IR) and Ultraviolet-Visible (UV-vis) spectra were theoretically simulated.

Main Results:

• Two UC6 isomers were found to possess similar energies, indicating potential coexistence in experiments.
• Topological analysis revealed predominantly closed-shell (ionic) U-C bonding with partial covalent character.
• The linear UC6 species exhibited a particularly notable degree of covalent character in its U-C bonds.
• Simulated IR and UV-vis spectra provide a basis for experimental isomer identification.

Conclusions:

• Computational methods successfully characterized UC6 isomers and their bonding.
• The findings suggest that multiple UC6 isomers can exist simultaneously.
• Theoretical spectra will aid in the experimental discovery and verification of UC6 structures.