Density functional theory and molecular bonding. III. Iron-series dimers

Binding energy curves for low-lying states of the 3d-dimers K2–Cu2 have been calculated using the density functional formalism with a local spin-density approximation for the exchange-correlation energy. Binding energy trends across the series are discussed as a competition between chemical bond formation and the reduction in spin-degeneracy which accompanies it. At the ends of the series, satisfactory agreement is found with available spectroscopic data. Both experimental and calculated binding energies show pronounced minima towards the center of the series, at Mn2 and Cr2, respectively. Discrepancies in binding energy trends are attributed to an incorrect description of s–d transfer inherent in the LSD approximation.