Acta Crystallographica Section B

Structural Science

Volume 57, Part 2 (April 2001)

research papers

Acta Cryst. (2001). B57, 136-141 [ doi:10.1107/S0108768100019923 ]

Synchrotron X-ray study of Er₃Al₅O₁₂ and Yb₃Al₅O₁₂ garnets

B. Etschmann, V. Streltsov, N. Ishizawa and E. N. Maslen

Abstract: Structure factors for Er₃Al₅O₁₂ and Yb₃Al₅O₁₂ garnets were measured using focused synchrotron X-radiation, with [lambda] = 0.7500 (2) and 0.7000 (2) Å, respectively. The difference electron density maps for Er₃Al₅O₁₂ and Yb₃Al₅O₁₂ were similar, as expected. This was attributed to the 4f electrons being shielded, which reduces their effectiveness in chemical bonding and the relative position of the rare-earth atoms in the periodic table. The symmetry of the difference electron density around the rare-earth atoms was found to reflect that of the cation geometry, emphasizing the importance of second nearest-neighbor interactions. This is consistent with the view that oxide-type structures may be regarded as a packed array of cations with anions in the interstices.

Keywords: synchrotron; garnets; electron density.