title: Ordering of vacancies in type-I tin clathrate: superstructure of Rb8Sn44 square2.
abstract: One important step toward the understanding of the mechanisms of thermoelectric properties is the knowledge about local distortions and vacancy ordering in clathrates. The type-I clathrate Rb8Sn44 shows in single-crystal and powder diffraction patterns a 2 x 2 x 2 supercell of the primitive cubic unit cell (Pmn), which originates from an ordering of the partially occupied site. The latter is distributed around a 41 screw axis, and the vacancies lead to a relaxation of the tin framework, thereby creating a local distortion of the tetrakaidecahedron.
authors.affiliation: Department Chemie, Technische Universität München, Lichtenbergstrasse 4, D-85747 Garching, Germany.
authors.forename: Franck
authors.initials: F
authors.lastname: Dubois
authors.forename: Thomas F
authors.initials: TF
authors.lastname: Fässler