title: Short-range order of compressed amorphous GeSe2.
abstract: The structure of amorphous GeSe2 (a-GeSe2) has been studied by means of a combination of two-edges X-ray absorption spectroscopy (XAS) and angle-dispersive X-ray diffraction under pressures up to about 30 GPa. Multiple-edge XAS data-analysis of a-GeSe2 at ambient conditions allowed us to reconstruct and compare the first-neighbor distribution function with previous results obtained by neutron diffraction with isotopic substitution. GeSe2 is found to remain amorphous up to the highest pressures attained, and a reversible 1.5 eV red-shift of the Ge K-edge energy indicating metallization, occurs between 10 GPa and 15 GPa. Two compression stages are identified by XAS structure refinement. First, a decrease of the first-neighbor distances up to about 10 GPa, in the same pressure region of a previously observed breakdown of the intermediate-range order. Second, an increase of the Ge-Se distances, bond disorder, and of the coordination number. This stage is related to a reversible non-isostructural transition involving a gradual conversion from tetra- to octa-hedral geometry which is not yet fully completed at 30 GPa.
authors.affiliation: 1] Physics Division, CNISM, School of Science and Technology, Università di Camerino, I-62032 Camerino (MC), Italy [2] Synchrotron Soleil, L'Orme des Merisiers, St. Aubin 91192 Gif s/Yvette, France.
authors.forename: L
authors.initials: L
authors.lastname: Properzi
authors.affiliation: Physics Division, CNISM, School of Science and Technology, Università di Camerino, I-62032 Camerino (MC), Italy.
authors.forename: A
authors.initials: A
authors.lastname: Di Cicco
authors.affiliation: Synchrotron Soleil, L'Orme des Merisiers, St. Aubin 91192 Gif s/Yvette, France.
authors.forename: L
authors.initials: L
authors.lastname: Nataf
authors.affiliation: Synchrotron Soleil, L'Orme des Merisiers, St. Aubin 91192 Gif s/Yvette, France.
authors.forename: F
authors.initials: F
authors.lastname: Baudelet
authors.affiliation: 1] Geodynamics Research Center, Ehime University, Matsuyama 790-8577, Japan [2] Earth-Life Science Institute, Tokyo Institute of Technology, Tokyo 152-8550, Japan.
authors.forename: T
authors.initials: T
authors.lastname: Irifune