Based on the density functional theory (DFT) combined with the broken symmetry (BS) approach, the magnetic coupling constant of the oxo-bridged iron (III) dimer [Cl_3FeOFeCl_3]~(2-) has been obtained under the various computational conditions in ADF code, including the numerical integration precision parameter, exchange-correlation energy functional and basis sets. The superexchange interactions between d~5- d~5 unpaired electrons were also discussed, and the antiferromagnetic coupling of the title compound was attributed to the superexchange pathway characterized by π~*/π~* and σ~* /σ~* ,. coming from the d_(yz) and d_(z~2) orbitals on Fe(III) ions and p orbital on μ-0 atom.

Key words: IRON COMPOUNDS, MAGNETISM, densityu functional theory, MOLECULAR ORBITAL THEORY