Calculation of the Refractive Indices of M1-xRxF2+x Crystals (M = Ca, Sr, Ba, Cd, Pb; R are Rare Earth Elements)

It is shown that the refractive indices of two-component M _1-x R _x F_2+x crystals (M = Ca, Sr, Ba, Cd, Pb; R = La-Lu, Y; 0 ≤ x ≤ 0.5) can be calculated with a rather high accuracy in a wide spectral range (depending on the rare-earth-element content) using molecular refraction additivity for the components.