Y2O3:Eu and the Mössbauer isomer shift coefficient of Eu compounds fromab-initiosimulations.

We report on a full potential density functional theory characterization of Y2O3upon Eu doping on the two inequivalent crystallographic sites 24dand 8b. We analyze local structural relaxation, electronic properties and the relative stability of the two sites. The simulations are used to extract the contact charge density at the Eu nucleus. Then we construct the experimental isomer shift (IS) versus contact charge density calibration curve, by considering an ample set of Eu compounds: EuF3, EuO, EuF2, EuS, EuSe, EuTe, EuPd3and the Eu metal. The, expected, linear dependence has a slope ofα= 0.054 mm s-1Å-3, which corresponds to nuclear expansion parameter ΔR/R= 6.0 × 10-5.αallows to obtain an unbiased and accurate estimation of the IS for any Eu compound. We test this approach on two mixed-valence compounds Eu3S4and Eu2SiN3, and use it to predict the Y2O3:Eu IS with the result +1.04 mm s-1at the 24dsite and +1.00 mm s-1at the 8bsite.