Atom distribution in SnSb2Te4 by resonant X-ray diffraction

The atom distribution in SnSb2Te4 (R (3) over barm, a = 4.298(1), c = 41.57(1) angstrom) has been elucidated by resonant single-crystal diffraction using synchrotron radiation with wavelengths near the K absorption edges of the elements present and additional non-resonant data. Refinement of site occupancies for all atoms on all sites was done with a joint refinement using five datasets. It shows that there is almost no anti-site disorder and no significant amount of vacancies. The cations are neither fully ordered nor randomly distributed. The 21R-type structure consists of rocksalt-type blocks separated by van der Waals gaps. Each block consists of four anion and three cation layers. Sn atoms are distributed over all cation sites but cluster in the middle of the blocks. (C) 2011 Elsevier Masson SAS. All rights reserved.