Unit Cell Parameter and Density Calculations for Sm1 –xRxF2 +x, Eu1 –xRxF2 +x, and Yb1 –xRxF2 +x (R Is a Rare-Earth Element) Crystals

Unit cell parameters a cal ( x ) and X-ray densities ρ X ( x ) are calculated in terms of a model that accounts for ionic bonding, additivity of properties, and dimensional factor upon aliovalent substitutions for 45 new nonstoichiometric phases Sm 1 − x R x F 2 + x , Eu 1 − x R x F 2 + x and Yb 1 − x R x F 2 + x (R = La−Lu, Y) based on SmF 2 , EuF 2 , and YbF 2 fluorite matrices (the fluorite CaF 2 type). A comparison of the calculated unit cell parameters a cal ( x ) and the experimental a ( x ) values available in the literature for these phases shows satisfactory match. Concentration-dependent relationships a cal ( x ) and ρ X ( x ) can be used for monitoring the composition of melt-grown Sm 1 − x R x F 2 + x , Eu 1 − x R x F 2 + x , and Yb 1 − x R x F 2 + x crystals in studies of their defect structures and fundamental properties.