Theoretical study of the Pu and Am dicarbide molecules

The electronic structure and ground-state molecular properties of Pu and Am dicarbides were investigated by relativistic multireference calculations using CASSCF/CASPT2 theory. The electronic ground state in both molecules corresponds to a symmetric triangular structure, in which the actinide atom is connected to a C2 moiety. The other experimentally relevant structure, the symmetric linear arrangement, is over 100 kJ/mol higher in energy. The bonding characteristics in the two structures were analysed on the basis of the valence molecular orbitals. Besides the usual 2-electron bonds some 1-electron bonding orbitals were also identified. We evaluated the electronic spectra with complete active space state interaction (CASSI) calculations taking into account spin-orbit coupling. The IR and Raman spectral characteristics were obtained using DFT calculations. Assessment of the present results with previously reported data on Th and U dicarbides provides information on the change of various molecular parameters in the actinide row.JRC.E.3-Materials researc