Theoretical Study of Thorium and Uranium Tetracarbide Molecules

The electronic structure and ground-state molecular properties of Th and U tetracarbides were investigated by relativistic multireference calculations using CASSCF/CASPT2 theory with an all-electron basis set as well as by density functional theory (B3LYP) in conjunction with relativistic pseudopotentials. The former calculations were extended with complete active space state interaction (CASSI) calculations accounting for spin–orbit coupling. The four carbon atoms can be arranged in various forms around the actinide atom resulting in ten structural isomers found altogether in our study. The electronic ground state in both molecules corresponds to a planar fan-type structure of C2v symmetry, in which the actinide atom is connected to a bent C4 moiety. Three structures arise from various arrangements of C2 moieties around the Th and U, while six isomers contain a C3 moiety and a lone C bonded to the actinide. The latter CAnC3-type structures are very high-energy structures (over 200 kJ/mol with respect to the ground state). The bonding characteristics in the most relevant structures were analysed on the basis of the valence molecular orbitals and Natural Bond Orbital method. We evaluated and interpreted the vibrational and electronic spectra. The present computed data of UC4 suggest a revision of the assignment of a previously observed IR absorption band to a different isomer.

POGANY Peter;  KOVACS Attila;  KONINGS Rudy; 

2014-03-03

WILEY-V C H VERLAG GMBH

JRC85361

1434-1948,   

http://onlinelibrary.wiley.com/doi/10.1002/ejic.201301425/abstract,    https://publications.jrc.ec.europa.eu/repository/handle/JRC85361,   

10.1002/ejic.201301425,