Atomic and electronic structures of hydrated polymolybdates by first principles calculations

First principles calculations of hydrated polymolybdates complexes have been made with an atomic orbital basis molecular orbital method. Hydration effects are taken into account by the conductor-like screening model (COSMO) using dielectric constant of water. Hydrated heptapolymolybdate, Mo ₇O₂₄^6-, shows a low symmetry structure, which agrees well to experimental results, i.e., X-ray diffraction of crystalline salts and X-ray absorption fine structure of the hydrated complex. Contrary to that, the hydrated heteropolymolybdate, NiMo₆O₂₄ ^10- prefer to exhibit the high symmetry structure. Inspection of the electronic states found that the Ni ion exhibits trivalent state or d ⁷ configuration in a formal sense. Jahn-Teller distortion around Ni is therefore evident. Such distortion cannot be found in CrMo₆O ₂₄^9- or CoMo₆O₂₄^9-.