Volume dependence of the effective ionic charge of alkaline-earth fluorides

The importance of the use of low temperature data with the second Szigeti relation is shown for the fluorite structure; a comparison with the NaCl and CsCl structures is given. The volume dependence of the generalized first Szigeti relation is used to calculate the Grüneisen parameter γ₁ with low temperature data; γ₁ is calculated with different models. Values of the volume dependence of the effective ionic charge are obtained independently using Hardy's model.