title: Hydrogen solubility in cristobalite at high pressure.
abstract: Powder samples of cristobalite-I are loaded with hydrogen at pressures up to 90 kbar and T = 250 °C and quenched under pressure to the liquid N2 temperature. The quenched samples are examined at ambient pressure by X-ray diffraction, Raman spectroscopy, and thermal desorption analysis. The hydrogen content of the samples is found to increase with pressure and reach a molecular ratio of H2/SiO2 ∼ 0.10 at P = 90 kbar. At ambient pressure, the samples consist of a mixture of approximately 80% cristobalite-I phase and 20% cristobalite-II-like phase, the crystal lattices of both phases being slightly expanded due to the hydrogen uptake. According to Raman spectroscopy, the hydrogen is dissolved in these phases in the form of H2 molecules.
authors.affiliation: Institute of Solid State Physics RAS , 142432 Chernogolovka, Moscow District, Russia.
authors.forename: Vadim S
authors.initials: VS
authors.lastname: Efimchenko
authors.forename: Vladimir K
authors.initials: VK
authors.lastname: Fedotov
authors.forename: Mikhail A
authors.initials: MA
authors.lastname: Kuzovnikov
authors.forename: Konstantin P
authors.initials: KP
authors.lastname: Meletov
authors.forename: Boris M
authors.initials: BM
authors.lastname: Bulychev
mesh_terms: D006859:Hydrogen / Q000737:chemistry*; D009584:Nitrogen / Q000737:chemistry; D011312:Pressure; D012822:Silicon Dioxide / Q000737:chemistry; D012995:Solubility; D013059:Spectrum Analysis, Raman; D013696:Temperature; D014961:X-Ray Diffraction
chemical_list: D012822:Silicon Dioxide; D006859:Hydrogen; D009584:Nitrogen