ELECTRONIC-STRUCTURE OF THE GROUP-V TETRAMERS (P4-BI4)

Complete active space multiconfiguration self-consistent field (CAS-MCSCF) followed by multireference configuration interaction (MRCI) and relativistic configuration interaction (RCI) calculations, which included up to 2 million configurations, are carried out on the ground and excited states of P4-Bi4. WE computed the properties of the 1A1 ground state with tetrahedral geometry as well as five excited states of triplet, singlet, and quintet multiplicities of these clusters. The computed results were used to assign the negative photo-detachment spectra of Sb4- and Bi4- as well as the matrix isolated spectra of small Bi clusters. We found spin-orbit effects were quite large for Bi4. Our computations are consistent with the recent reassignment of the spectra of Bi4 observed by Bondybey and English to Bi3.