title: Pressure study of monoclinic ReO2 up to 1.2 GPa using X-ray absorption spectroscopy and X-ray diffraction.
abstract: The crystal and local atomic structure of monoclinic ReO2 (alpha-ReO2) under hydrostatic pressure up to 1.2 GPa was investigated for the first time using both X-ray absorption spectroscopy and high-resolution synchrotron X-ray powder diffraction and a home-built B4C anvil pressure cell developed for this purpose. Extended X-ray absorption fine-structure (EXAFS) data analysis at pressures from ambient up to 1.2 GPa indicates that there are two distinct Re-Re distances and a distorted ReO6 octahedron in the alpha-ReO2 structure. X-ray diffraction analysis at ambient pressure revealed an unambiguous solution for the crystal structure of the alpha-phase, demonstrating a modulation of the Re-Re distances. The relatively small portion of the diffraction pattern accessed in the pressure-dependent measurements does not allow for a detailed study of the crystal structure of alpha-ReO2 under pressure. Nonetheless, a shift and reduction in the (011) Bragg peak intensity between 0.4 and 1.2 GPa is observed, with correlation to a decrease in Re-Re distance modulation, as confirmed by EXAFS analysis in the same pressure range. This behavior reveals that alpha-ReO2 is a possible inner pressure gauge for future experiments up to 1.2 GPa.
authors.affiliation: Laboratório Nacional de Luz Síncrotron, Caixa Postal 6192, CEP 13083-970, Campinas, SP, Brazil. furlan@lnls.br
authors.forename: Fabio Furlan
authors.initials: FF
authors.lastname: Ferreira
authors.forename: Hamilton P S
authors.initials: HP
authors.lastname: Corrêa
authors.forename: Marcos T D
authors.initials: MT
authors.lastname: Orlando
authors.forename: José L
authors.initials: JL
authors.lastname: Passamai
authors.forename: Cíntia G P
authors.initials: CG
authors.lastname: Orlando
authors.forename: Isabela P
authors.initials: IP
authors.lastname: Cavalcante
authors.forename: Flávio
authors.initials: F
authors.lastname: Garcia
authors.forename: Edilson
authors.initials: E
authors.lastname: Tamura
authors.forename: Luis G
authors.initials: LG
authors.lastname: Martinez
authors.forename: Jesualdo L
authors.initials: JL
authors.lastname: Rossi
authors.forename: Francisco C L
authors.initials: FC
authors.lastname: de Melo