title: High-pressure powder neutron diffraction study on lead scandium niobate.
abstract: The structural evolution of PbSc(0.5)Nb(0.5)O(3) (PSN) under pressure has been studied by in situ powder neutron diffraction. Rietveld refinements to the data show that the continuous phase transition detected by x-ray diffraction at p(c) = 4.1 GPa (Maier et al 2010 Phys. Rev. B 81 174116) is associated with long-range ordering of antiphase octahedral tilts and local ordering of ferroic Pb displacements. Similar to PbSc(0.5)Ta(0.5)O(3) (PST) (Maier et al 2010 Acta Crystallogr. 66 280-91), antiphase octahedral tilting even exists below the critical pressure in a regime in which the structure retains a cubic metric. In contrast to PST, in which the Pb atomic displacement parameters (DPs) form ellipsoids elongated along the cubic {111} directions, the atomic DPs of Pb in PSN form flattened discs parallel to the cubic {111}-planes. This indicates that in PST the Pb displacements are along the cubic {111} directions, whereas in PSN the local Pb displacements are randomly distributed along the cubic {110} directions. The latter can be explained by the abundance of underbonded oxygen atoms associated with the chemical B-site disorder.
authors.affiliation: Mineralogisch-Petrographisches Institut, Universität Hamburg, 20146 Hamburg, Germany. bernd.maier@uni-hamburg.de
authors.forename: B J
authors.initials: BJ
authors.lastname: Maier
authors.forename: R J
authors.initials: RJ
authors.lastname: Angel
authors.forename: B
authors.initials: B
authors.lastname: Mihailova
authors.forename: W G
authors.initials: WG
authors.lastname: Marshall
authors.forename: M
authors.initials: M
authors.lastname: Gospodinov
authors.forename: U
authors.initials: U
authors.lastname: Bismayer