Theoretical explanation of the g factor for Cr4+ in Y2SiO5 crystal

The g factor of Cr4+ in Y2SiO5 crystal is calculated from a completed high-order perturbation formula, in which not only the conventional contribution to the g-shift Δg(=g−ge) from the crystal-field mechanism, but also the contribution from the charge-transfer mechanism (which is neglected in the crystal-field theory) are considered. The calculated result shows good agreement with the observed value. It is found that the calculated Δg due to the charge-transfer mechanism is opposite in sign and about 38% in magnitude, compared with that due to the crystal-field mechanism. So, in the studies of the g factor for a 3dn ion having high valence state in crystals, the contribution due to the charge-transfer mechanism should be taken into account.