title: High-pressure transformations in xenon hydrates.
abstract: A high-pressure investigation of the Xe*H(2)O chemical system was conducted by using diamond-anvil cell techniques combined with in situ Raman spectroscopy, synchrotron x-ray diffraction, and laser heating. Structure I xenon clathrate was observed to be stable up to 1.8 GPa, at which pressure it transforms to a new Xe clathrate phase stable up to 2.5 GPa before breaking down to ice VII plus solid xenon. The bulk modulus and structure of both phases were determined: 9 +/- 1 GPa for Xe clathrate A with structure I (cubic, a = 11.595 +/- 0.003 A, V = 1,558.9 +/- 1.2 A(3) at 1.1 GPa) and 45 +/- 5 GPa for Xe clathrate B (tetragonal, a = 8.320 +/- 0.004 A, c = 10.287 +/- 0.007 A, V = 712.1 +/- 1.2 A(3) at 2.2 GPa). The extended pressure stability field of Xe clathrate structure I (A) and the discovery of a second Xe clathrate (B) above 1.8 GPa have implications for xenon in terrestrial and planetary interiors.
authors.affiliation: Geophysical Laboratory and Center for High Pressure Research, Carnegie Institution of Washington, 5251 Broad Branch Road NW, Washington DC 20015, USA.
authors.forename: Chrystèle
authors.initials: C
authors.lastname: Sanloup
authors.forename: Ho-kwang
authors.initials: HK
authors.lastname: Mao Hk
authors.forename: Russell J
authors.initials: RJ
authors.lastname: Hemley
mesh_terms: D055592:Biophysical Phenomena; D001703:Biophysics; D007834:Lasers; D008027:Light; D011312:Pressure; D013059:Spectrum Analysis, Raman; D014867:Water / Q000737:chemistry; D014961:X-Ray Diffraction; D014978:Xenon / Q000737:chemistry*
chemical_list: D014867:Water; D014978:Xenon