title: Ordering and dynamics of the central tetrahedron in the 1/1 Zn6Sc periodic approximant to quasicrystal.
abstract: Periodic approximants to quasicrystals offer a unique opportunity to better understand the structure, physical properties and stabilizing mechanisms of their quasicrystal counterparts. We present a detailed study of the order-disorder phase transition occurring at about 160 K in the Zn(6)Sc cubic approximant to the icosahedral quasicrystal i-MgZnSc. This transition goes along with an anti-parallel ordering of the tetrahedra located at the centres of large atomic clusters, which are packed on a bcc lattice. Single crystal x-ray diffuse scattering shows that the tetrahedra display pre-transitional short range ordering above T(c) (Yamada et al 2012 in preparation). Using quasielastic neutron scattering (QENS) we clearly evidence this short range order to be dynamical in nature above T(c). The QENS data are consistent with a model of tetrahedra 'jumping' between almost equivalent positions, which is supported by molecular dynamics simulations. This demonstrates a unique dynamical flexibility of the Zn(6)Sc structure even at room temperature.
authors.affiliation: Institut für Theoretische und Angewandte Physik, Universität Stuttgart, Stuttgart, Germany. euchner@itap.physik.uni-stuttgart.de
authors.forename: Holger
authors.initials: H
authors.lastname: Euchner
authors.forename: Tsunetomo
authors.initials: T
authors.lastname: Yamada
authors.forename: Helmut
authors.initials: H
authors.lastname: Schober
authors.forename: Stephane
authors.initials: S
authors.lastname: Rols
authors.forename: Marek
authors.initials: M
authors.lastname: Mihalkovič
authors.forename: Ryuji
authors.initials: R
authors.lastname: Tamura
authors.forename: Tsutomu
authors.initials: T
authors.lastname: Ishimasa
authors.forename: Marc
authors.initials: M
authors.lastname: de Boissieu