Density functional theory study on magnetic interactions in the V 3+ dimer complexes

摘要

The magnetic interactions in the V_2Cl 93- cluster is investigated as an example of the orbitally degenerate d~2-d ~2 transition metal dimer complexes. The local orbital functions are defined by linear combinations of the molecular orbital functions which are calculated by the density functional theory. These local orbitals are used as basis of the matrix of an effective Hamiltonian. To evaluate the parameters of the effective Hamiltonian, the total energies in the single Slater determinants of the all possible configurations are calculated. Especially to obtain the one-body energies and Coulomb integrals separately, the total energies in the states of the configurations with a noninteger occupation numbers are also calculated. One parameter remains as a fitting parameter Δ, which is the difference between the one-body energies of two local orbitals a_1 and e under C_(3v) site symmetry. The temperature dependence of the magnetic susceptibility for some values of Δ are shown. Theoretical studies of the magnetic interactions in transition metal dimer complexes are often based on the assumption that the d-electrons are localized near the metal centers. As this is not always the case a new theoretical framework is needed. An Effective Hamiltonian method, based on the DFT-based ligand field model, is used to overcome this limitation and applied in this article to the study of Vanadium dimer complexes.