Spin-orbit effects on the optical and magnetic properties of cerium (III) hexahalides

摘要

In this work we study the [CeX_6]~(3-), X = Cl, Br, I octahedral complexes. The DFT geometry optimizations and the molecular properties calculations were performed using the PBE functional and TZ2P basis set through the use of the two-component ZORA Hamiltonian to include the scalar and spin-orbit relativistic effects. The optimized structures were used in the four-component SCF DSW code to calculate the molecular orbital energies and the paramagnetic resonance (giso and Ahfi) parameters. These results are in agreement with cerium chlorine-elpasolite (Cs _2NaCeCl_6) experimental studies. Experimentally, the ground state span the Γ_(7u) symmetry in octahedral geometry, and the excited states give rise to four "4f-4f" type transitions and three "4f-5d" type transitions. The correct descriptions of such transitions are only possible by calculations which include spin-orbit coupling effects, such as, the four-component Dirac equation or its two-component ZORA approximation. Such results confirm the need to include relativistic effects in the calculations of optical and magnetic properties in these lanthanide complexes. These results are in agreement with the spectrochemical series, in which the effect of the ligands follows the usual order: Cl- > Br- > I-.