Michel van Veenendaal

Model of Ultrafast Intersystem Crossing in Photoexcited Transition-Metal Organic Compounds

The mechanism behind fast intersystem crossing in transition-metal complexes is shown to be a result of the dephasing of the photoexcited state to the phonon continuum of a different state with a significantly different transition metal-ligand distance. The coupling is a result of the spin-orbit interaction causing a change in the local moment. Recurrence to the initial state is prevented by the damping of the phonon oscillation. The decay time is faster than the oscillation frequency of the transition metal-ligand stretch mode, in agreement with experiment. For energies above the region where the strongest coupling occurs, a slower “leakage”-type decay is observed. If the photoexcited state is lower in energy than the state it couples to, then there is no decay.

Electronic Structure of Low-Dimensional 4d5 Oxides: Interplay of Ligand Distortions, Overall Lattice Anisotropy, and Spin–Orbit Interactions

The electronic structure of the low-dimensional 4d(5) oxides Sr2RhO4 and Ca3CoRhO6 is herein investigated by embedded-cluster quantum chemistry calculations. A negative tetragonal-like t2g splitting is computed in Sr2RhO4 and a negative trigonal-like splitting is predicted for Ca3CoRhO6, in spite of having positive tetragonal distortions in the former material and cubic oxygen octahedra in the latter. Our findings bring to the foreground the role of longer-range crystalline anisotropy in generating noncubic potentials that compete with local distortions of the ligand cage, an issue not addressed in standard textbooks on crystal-field theory. We also show that sizable t2g(5)-t2g(4)eg(1) couplings via spin-orbit interactions produce in Sr2RhO4 ⟨Z⟩ = ⟨Σ(i)l(i)·s(i)⟩ ground-state expectation values significantly larger than 1, quite similar to theoretical and experimental data for 5d(5) spin-orbit-driven oxides such as Sr2IrO4. On the other hand, in Ca3CoRhO6, the ⟨Z⟩ values are lower because of larger t2g-eg splittings. Future X-ray magnetic circular dichroism experiments on these 4d oxides will constitute a direct test for the ⟨Z⟩ values that we predict here, the importance of many-body t2g-eg couplings mediated by spin-orbit interactions, and the role of low-symmetry fields associated with the extended surroundings.

Mixed configuration ground state in iron(II) phthalocyanine

We calculate the angular dependence of the x-ray linear and circular dichroism at the

Soft X-ray fluorescence yield XMCD sum rules

L_{2,3}

Photoinduced magnetism caused by charge-transfer excitations in tetracyanoethylene-based organic magnets

edges of

Spin-moment formation and reduced orbital polarization in LaNiO3/LaAlO3 superlattice: LDA+U study

\alpha

Xclaim: A graphical interface for the calculation of core-hole spectroscopies

-Fe(II) Phthalocyanine (FePc) thin films using a ligand field model with full configuration interaction. We find the best agreement with the experimental spectra for a mixed ground state of

Electronic structure and orbital polarization of LaNiO3 with a reduced coordination and under strain: A first-principles study

^3E_{g}(a_{1g}^2e_g^3b_{2g}^1)

Fractionalization, entanglement, and separation: Understanding the collective excitations in a spin-orbital chain

and

The choice of internal coordinates in complex chemical systems

^3B_{2g}(a_{1g}^1e_g^4b_{2g}^1)