Estimating the 2Eg energy state for Cr3+ in solids by using the nephelauxetic function he

The nephelauxetic function he is calculated at the octahedral crystal site occupied by the Cr3+ ion in 89 oxides and 17 fluorides and is incorporated in an equation of the form where K and α are obtained by adjustment to experimental data and Ef relates to the energy of the 4A2g ↔ 2Eg zero phonon transition in the free ion. With this method, the energy position of the 2Eg state of Cr3+ can be estimated. The experimental data are shown to be reproduced for 99 of the 106 selected compounds with an accuracy of cm−1, considering ≈0.4 < he < ≈ 0.6 in fluorides and ≈1 < he < ≈ 2 in oxides. The 7 situations where the model fails are examined.