Structural relaxations around Ti, Cr and Fe impurities in alpha-Al2O3 probed by x-ray absorption near edge structure combined with first-principles calculations

Emilie Gaudry (1) , Delphine Cabaret (1) , Philippe Sainctavit (1) , Christian Brouder (1) , Francesco Mauri (1) , José Goulon (2) , Andrei Rogalev (2)

1 LMCP - Laboratoire de minéralogie, cristallographie de Paris
2 ESRF - European Synchrotron Radiation Facility

We determine the structural relaxations around paramagnetic impurities (Ti, Cr, Fe) in corundum (alpha-Al2O3), by combining x-ray absorption near edge structure (XANES) experiments and ab initio calculations. The structural relaxations are found to be very local. We then show that XANES is sensitive to small variations in interatomic distances within the coordination shell of the absorbing atom. The experiments were carried out on single crystals of ruby and sapphires. Linear dichroic signals are essential to characterize the geometry of the impurity site. The calculations were performed within a self-consistent ''non muffin-tin'' framework, that uses pseudopotentials, plane-wave basis set, and the continued fraction for the absorption cross section.

Mots clés: sapphires; impurities; structural relaxation; angular dependence; XANES; K edge; ab initio calculations; pseudopotentials; ruby

Domaines: Science des matériaux [cond-mat.mtrl-sci]

Emilie Gaudry, Delphine Cabaret, Philippe Sainctavit, Christian Brouder, Francesco Mauri, et al.. Structural relaxations around Ti, Cr and Fe impurities in alpha-Al2O3 probed by x-ray absorption near edge structure combined with first-principles calculations. Journal of Physics: Condensed Matter, 2005, 17, pp.5467-5480. ⟨10.1088/0953-8984/17/36/003⟩. ⟨hal-00003882⟩