title: A high-pressure single-crystal synchrotron diffraction study of NH4RbTe4O9·2H2O: stability of three different TeO(x) coordination polyhedra.
abstract: The crystal structure of ammonium rubidium nonaoxotetratellurate(IV) dihydrate has been studied as a function of pressure up to 7.40 GPa. The ambient-pressure structure is characterized by the co-existence of three different Te-O polyhedra (TeO(3), TeO(4) and TeO(5)), which are connected to form layers. NH(4)(+), H(2)O and Rb(+) are incorporated between the layers. Both the Rb1 position, which is located on a twofold axis, and the Rb2 position are partially occupied. The three different types of coordination polyhedra around Te(4+) are stable up to at least 5.05 GPa. No phase transition is observed. The fit of the unit-cell volume as a function of pressure gives a zero-pressure bulk modulus of 34 (1) GPa with a zero-pressure volume of V(0) = 2620 (4) Å(3) [B' = 1.4 (2)].
authors: Departamento Física Materia Condensada, Facultad de Ciencia y Tecnología, Universidad del País Vasco, Apartado 644, E-48080 Bilbao, Spain. karen.friese@ehu.es
authors: K
authors: K
authors: Friese
authors: P S
authors: PS
authors: Halasyamani
authors: M
authors: M
authors: Tolkiehn
authors: A
authors: A
authors: Grzechnik