First-Principles Analysis of the Rb₂CrF₆ Absorption Spectrum

A systematic first-principles analysis of the energy level scheme and absorption spectrum of Cr⁴+ in Rb₂CrF₆ crystal is presented. The recently developed first-principles approach to the analysis of the absorption spectra of ions in crystals based on the discrete variational multi-electron (DV-ME) method was used in the calculations. The method is based on the numerical solution of the Dirac equation and has a wide area of applicability. As a result, the complete energy level scheme of Cr⁴+ and its absorption spectrum were calculated, assigned and compared with available experimental literature data on the ground state absorption. Numerical contributions of all possible electron configurations to the wave functions of the calculated states were determined. By analysing the molecular orbitals population, numerical contributions of the fluorine 2p- and 2s-orbitals to the 3d-molecular orbitals were determined. The significant contribution of the ligand's wave functions shows the high degree of covalency in the considered crystal. -PACS numbers: 71.70.Ch, 71.70.Ej.