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Title

DFT-Based Studies on the Jahn-Teller Effect in 3d Hexacyanometalates with Orbitally Degenerate Ground States

Authors
Atanasov, Mihial
Comba, P.
Daul, C. A.
Published in Journal of Physical Chemistry. A. 2007, vol. 111, no. 37, p. 9145-9163
Abstract The topology of the ground-state potential energy surface of M(CN)6 with orbitally degenerate 2T2g (M = TiIII (t2g1), FeIII and MnII (both low-spin t2g5)) and 3T1g ground states (M = VIII (t2g2), MnIII and CrII (both low-spin t2g4)) has been studied with linear and quadratic Jahn−Teller coupling models in the five-dimensional space of the εg and τ2g octahedral vibrations (Tg(εg+τ2g) Jahn−Teller coupling problem (Tg = 2T2g, 3T1g)). A procedure is proposed to give access to all vibronic coupling parameters from geometry optimization with density functional theory (DFT) and the energies of a restricted number of Slater determinants, derived from electron replacements within the t2g1,5 or t2g2,4 ground-state electronic configurations. The results show that coupling to the τ2g bending mode is dominant and leads to a stabilization of D3d structures (absolute minima on the ground-state potential energy surface) for all complexes considered, except for [Ti(CN)6]3-, where the minimum is of D4h symmetry. The Jahn−Teller stabilization energies for the D3d minima are found to increase in the order of increasing CN−M π back-donation (TiIII < VIII < MnIII < FeIII < MnII < CrII). With the angular overlap model and bonding parameters derived from angular distortions, which correspond to the stable D3d minima, the effect of configuration interaction and spin−orbit coupling on the ground-state potential energy surface is explored. This approach is used to correlate Jahn−Teller distortion parameters with structures from X-ray diffraction data. Jahn−Teller coupling to trigonal modes is also used to reinterpret the anisotropy of magnetic susceptibilities and g tensors of [Fe(CN)6]3-, and the 3T1g ground-state splitting of [Mn(CN)6]3-, deduced from near-IR spectra. The implications of the pseudo Jahn−Teller coupling due to t2g−eg orbital mixing via the trigonal modes (τ2g) and the effect of the dynamic Jahn−Teller coupling on the magnetic susceptibilities and g tensors of [Fe(CN)6]3- are also addressed.
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Research group Groupe Hauser
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ATANASOV, Mihial et al. DFT-Based Studies on the Jahn-Teller Effect in 3d Hexacyanometalates with Orbitally Degenerate Ground States. In: Journal of Physical Chemistry. A, 2007, vol. 111, n° 37, p. 9145-9163. https://archive-ouverte.unige.ch/unige:3584

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Deposited on : 2009-10-02

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