title: Theory of High-Spin d(4) Complexes: An Angular-Overlap Model Parametrization of the Ligand Field in Vibronic-Coupling Calculations.
abstract: A new theoretical approach for the calculation of the electronic and molecular structures of octahedrally-coordinated high-spin d(4) complexes is described. A prescription for the construction of an effective (3)T1 + (5)E (O) Hamiltonian from the ligand-field matrices of a complex with general trigonal symmetry is given, where the ligand field is parametrized in terms of the angular-overlap model (AOM). The Jahn-Teller matrices for the (3)T1 + ((5)E⊗e) vibronic Hamiltonian are constructed and the lowest eigenvalues are calculated by a numerical method. The model obviates the need to assume a temperature dependence of bonding parameters, inherent to the conventional ligand-field-theory approach and is applicable over the whole range of vibronic-coupling strengths, as demonstrated by example calculations on the [Mn(OD2)6](3+) cation and MgO:Cr(2+).
authors.affiliation: Laboratory for Neutron Scattering, PSI, CH-5232 Villigen, Switzerland, Department of Chemistry and Biochemistry, University of Bern, Freiestrasse 3, CH-3012 Bern, Switzerland, and Centre for Magnetic Resonance, The University of Queensland, Brisbane, Australia.
authors.forename: Graham
authors.initials: G
authors.lastname: Carver
authors.affiliation: Laboratory for Neutron Scattering, PSI, CH-5232 Villigen, Switzerland, Department of Chemistry and Biochemistry, University of Bern, Freiestrasse 3, CH-3012 Bern, Switzerland, and Centre for Magnetic Resonance, The University of Queensland, Brisbane, Australia.
authors.forename: Markus
authors.initials: M
authors.lastname: Thut
authors.affiliation: Laboratory for Neutron Scattering, PSI, CH-5232 Villigen, Switzerland, Department of Chemistry and Biochemistry, University of Bern, Freiestrasse 3, CH-3012 Bern, Switzerland, and Centre for Magnetic Resonance, The University of Queensland, Brisbane, Australia.
authors.forename: Christopher
authors.initials: C
authors.lastname: Noble
authors.affiliation: Laboratory for Neutron Scattering, PSI, CH-5232 Villigen, Switzerland, Department of Chemistry and Biochemistry, University of Bern, Freiestrasse 3, CH-3012 Bern, Switzerland, and Centre for Magnetic Resonance, The University of Queensland, Brisbane, Australia.
authors.forename: Philip L W
authors.initials: PL
authors.lastname: Tregenna-Piggott