Title :

Improvement of the ab initio embedded cluster method for luminescence properties of doped materials by taking into account long-range impurity induced distortions: the example of Y₂O₃:Bi³⁺

Author(s) :

Réal, Florent [Auteur]
Laboratoire de Physique des Lasers, Atomes et Molécules - UMR 8523 [PhLAM]
Ordejón, Belén [Auteur]
Laboratoire de Physique des Lasers, Atomes et Molécules - UMR 8523 [PhLAM]
Vallet, Valérie [Auteur]
Laboratoire de Physique des Lasers, Atomes et Molécules - UMR 8523 [PhLAM]
Flament, Jean-Pierre [Auteur]
Laboratoire de Physique des Lasers, Atomes et Molécules - UMR 8523 [PhLAM]
Schamps, Joël [Auteur]
Laboratoire de Physique des Lasers, Atomes et Molécules - UMR 8523 [PhLAM]

Journal title :

The Journal of Chemical Physics

Pages :

194501

Publisher :

American Institute of Physics

Publication date :

2009-11-16

ISSN :

0021-9606

English keyword(s) :

bismuth
luminescence
ab initio
embedded cluster
correlation
relativity

HAL domain(s) :

Physique [physics]/Physique [physics]/Chimie-Physique [physics.chem-ph]

English abstract : [en]

New ab initio embedded-cluster calculations devoted to simulating the electronic spectroscopy of Bi³⁺ impurities in Y₂O₃ sesquioxide for substitutions in either S₆ or C₂ ...
Show more >New ab initio embedded-cluster calculations devoted to simulating the electronic spectroscopy of Bi³⁺ impurities in Y₂O₃ sesquioxide for substitutions in either S₆ or C₂ cationic sites have been carried out taking special care of the quality of the environment. A considerable quantitative improvement with respect to previous studies [F. Réal et al. J. Chem. Phys. <b>125</b>, 174709 (2006); F. Réal et al. J. Chem. Phys. <b>127</b>, 104705 (2007)] is brought by using environments of the impurities obtained via supercell techniques that allow the whole (pseudo) crystal to relax (WCR geometries) instead of environments obtained from local relaxation of the first coordination shell only (FSR geometries) within the embedded cluster approach, as was done previously. In particular the uniform 0.4 eV discrepancy of absorption energies found previously with FSR environments disappears completely when the new WCR environments of the impurities are employed. Moreover emission energies and hence Stokes shifts are in much better agreement with experiment. These decisive improvements are mainly due to a lowering of the local point-group symmetry (S₆ → C₃ and C₂ → C₁) when relaxing the geometry of the emitting (lowest) triplet state. This symmetry lowering was not observed in FSR embedded cluster relaxations because the crystal field of the embedding frozen at the genuine pure crystal positions seems to be a more important driving force than the interactions within the cluster, thus constraining the overall symmetry of the system. Variations of the doping rate are found to have negligible influence on the spectra. In conclusion, the use of WCR environments may be crucial to render the structural distortions occurring in a doped crystal and it may help to significantly improve the embedded-cluster methodology to reach the quantitative accuracy necessary to interpret and predict luminescence properties of doped materials of this type.Show less >

Language :

Anglais

Popular science :

Non

Comment :

17 pages

Collections :

• Laboratoire de Physique des Lasers, Atomes et Molécules (PhLAM) - UMR 8523

Source :

Harvested from HAL