Applications to the Ground State of Permanganate and Related Tetroxo Systems

4 Applications to the Ground State of Permanganate and Related Tetroxo Systems 

The methods described above have been applied to ground state properties of a large number of complexes. These properties include parameters from infrared 

The permanganate anion MnC)4 has a tetrahedral geometry with a Td point group symmetry, Fig. 1. At each oxygen atom, we have a core like 2s orbital as well as two 2-pn and one 2pffvalance orbitals. The total number of valence electrons is 32 of which 8 are in core type 2s levels and the remaining 24 in molecular orbitals spanned by 2pn, 2pa and 3d. We show in Fig. 2 the levels represented by orbitals made up of 2pn, 2pa and 3d. 

At the HF-level, Mn04 is unstable with respect to dissociation into one electron and the neutral species. Introducing post-HF calculations makes Mn04 stable with respect to such a dissociation. The problems encountered for HF in 3d metal complexes are not present in systems involving nd (n = 4,5) elements since the corresponding ns, np orbitals are much more contracted than nd for n = 4,5. Also, the HF error seems to be more severe for late 3d elements than early 3d elements. 

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