Electronic properties of rhenium, osmium and iridium dimers by density functional methods

Bond distance, vibrational frequency and dissociation energy of Re2, Os2 and Ir2 were studied by density functional methods B3LYP, BLYP, B3PW91, BHLYP, BP86, B3P86 and PBE1PBE. Spin multiplicity 7 is the ground state for Os2, 5 for Ir2. For Re2, the ground state spin multiplicity is sensitive to the density functionals. Spin multiplicity 5 is the ground state for B3LYP, B3PW91, B3P86, and PBE1PBE, while triplet state is the ground state for BLYP, BP86, and BHLYP. The calculated bond distances are less sensitive to the methods used, while it is not true for vibrational frequencies and dissociation energies.