Abstract
We report on a full potential density functional theory characterization of Y2O3 upon Eu doping on the two inequivalent crystallographic sites 24d and 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, EuPd3 and the Eu metal. The, expected, linear dependence has a slope of α = 0.054 mm s−1 Å− 3, which corresponds to nuclear expansion parameter ΔR/R = 6.0 × 10−5. α allows to obtain an unbiased and accurate estimation of the IS for any Eu compound. We test this approach on two mixed-valence compounds Eu3S4 and Eu2SiN3, and use it to predict the Y2O3:Eu IS with the result +1.04 mm s−1 at the 24d site and +1.00 mm s−1 at the 8b site.
Highlights
Yttrium sesquioxide doped with lanthanide ions are technologically relevant materials with a broad set of applications, especially owing to their luminescence properties [1]
We report on a full potential density functional theory characterization of Y2O3 upon Eu doping on the two inequivalent crystallographic sites 24d and 8b
The, expected, linear dependence has a slope of α = 0.054 mm s−1 Å−3, which corresponds to nuclear expansion parameter ΔR/R = 6.0 × 10−5. α allows to obtain an unbiased and accurate estimation of the isomer shift (IS) for any Eu compound
Summary
We perform density functional [9, 10] theory simulations within the all-electron full-potential linearised augmentedplanewave (FP-LAPW) method [11], as implemented in the elk [12] code. Exchange correlation (xc) effects are included in the local spin density approximation (LSDA) and the LSDA + U method, where a Hubbard U correction [13] is applied to the Eu f -shell. Numerical results were obtained by fully minimizing internal forces, while Bravais lattice parameters are linearly interpolated, as a function of Eu content, from those of the parent compounds Y2O3 and Eu2O3 (10.602 and 10.859 Å respectively [17]). All other systems studied in this work (listed in the text and used to obtain figure 3) have been studied at the experimental lattice positions and using the same computational parameters and methods as above, as well as a dense reciprocal space discretization
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