Fe dimers: A theoretical study of the hyperfine interactions

The electronic structures of diatomic molecules ${\mathrm{Fe}}_2$ and $\mathrm{Fe}M$, where $M=\mathrm{M}\mathrm{n},\mathrm{ }\mathrm{C}\mathrm{o},\mathrm{ }\mathrm{N}\mathrm{i},\mathrm{ }\mathrm{and}\mathrm{ }\mathrm{Cu}$, are investigated by molecular-orbital calculations using a discrete variational method and a local approximation for the exchange interaction. The one-electron wave functions obtained are used to calculate electric-field gradients, electronic charge and spin densities at the Fe nucleus and spin-dipolar hyperfine fields, which are related to measured hyperfine parameters reported from experiments in solid inert-gas matrices. Molecular-orbital energy schemes and population analysis are presented. These and other aspects of the electronic structure of the $\mathrm{Fe}M$ molecules are used in a qualitative interpretation of the hyperfine data; in some cases suggestions are given for the ground-state configuration.