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X-ray absorption spectroscopy of geo 2 glass to 64 gpa

Hong, Xinguo ; Newville, Matthew ; Duffy, Thomas S ; Sutton, Stephen R ; Rivers, Mark L

Journal of Physics: Condensed Matter, 2014, Vol.26(3), p.035104 (9pp) [Tạp chí có phản biện]

ISSN: 0953-8984 ; E-ISSN: 1361-648X ; DOI: 10.1088/0953-8984/26/3/035104

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  • Nhan đề:
    X-ray absorption spectroscopy of geo 2 glass to 64 gpa
  • Tác giả: Hong, Xinguo ; Newville, Matthew ; Duffy, Thomas S ; Sutton, Stephen R ; Rivers, Mark L
  • Là 1 phần của: Journal of Physics: Condensed Matter, 2014, Vol.26(3), p.035104 (9pp)
  • Mô tả: The structural behavior of GeO 2 glass has been investigated up to 64 GPa using results from x-ray absorption spectroscopy in a diamond anvil cell combined with previously reported density measurements. The difference between the nearest Ge–O distances of glassy and rutile-type GeO 2 disappears at the Ge–O distance maximum at 20 GPa, indicating completion of the tetrahedral–octahedral transition in GeO 2 glass. The mean-square displacement σ 2 of the Ge–O distance in the first Ge–O shell increases progressively to a maximum at 10 GPa, followed by a substantial reduction at higher pressures. The octahedral glass is, as expected, less dense and has a higher compressibility than the corresponding crystalline phase, but the differences in Ge–O distance and density between the glass and the crystals are gradually eliminated over the 20–40 GPa pressure range. Above 40 GPa, GeO 2 forms a dense octahedral glass with a compressibility similar to that of the corresponding crystalline phase (α-PbO 2 type). The EXAFS and XANES spectra show evidence for subtle changes in the dense glass continuing to occur at these high pressures. The Ge–O bond distance shows little change between 45–64 GPa, and this may reflect a balance between bond shortening and a gradual coordination number increase with compression. The density of the glass is similar to that of the α–PbO 2 -type phase, but the Ge–O distance is longer and is close to that in the higher-coordination pyrite-type phase which is stable above ∼60 GPa. The density data provide evidence for a possible discontinuity and change in compressibility at 40–45 GPa, but there are no major changes in the corresponding EXAFS spectra. A pyrite-type local structural model for the glass can provide a reasonable fitting to the XAFS spectra at 64 GPa.
  • Ngôn ngữ: English
  • Số nhận dạng: ISSN: 0953-8984 ; E-ISSN: 1361-648X ; DOI: 10.1088/0953-8984/26/3/035104

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