Crystal field effects and electron-phonon interaction in K2LiAlF6:Cr3+

The crystal field effects and electron-phonon interaction in K2LiAlF6:Cr3+ elpasolite crystal were studied using the exchange charge model (ECM) of crystal field and harmonic approximation of lattice vibrations. The crystal field parameters (CFP) and energy level scheme for the [CrF6]3− cluster were calculated. As a further application of the ECM, the crystal field strength 10Dq was studied for different “impurity ion-ligand” distances R. By fitting these values to the power law 10Dq≈R−n of coordinate R, the value of n was obtained as 4.56796. Several physical quantities (such as the electron-vibrational interaction constants, Stokes shifts, Huang-Rhys factors and Jahn-Teller stabilization energy) associated with the two normal vibrational modes a1g and eg of the [CrF6]3− complex coupled with the Cr3+ electronic states, were calculated. The obtained results are compared with experimental data and discussed.