title: Synchrotron X-ray Diffraction Measurements of Single-Crystal Hydrogen to 26.5 Gigapascals.
abstract: The crystal structure and equation of state of solid hydrogen have been determined directly to 26.5 gigapascals at room temperature by new synchrotron x-ray diffraction techniques. Solid hydrogen remains in the hexagonal close-packed structure under these pressure-temperature conditions and exhibits increasing structural anisotropy with pressure. The pressure-volume curve determined from the x-ray data represents the most accurate experimental measurement of the equation of state to date in this pressure range. The results remove the discrepancy between earlier indirect determinations and provide a new experimental constraint on the molecular-to-atomic transition predicted at higher pressures.
authors.forename: H K
authors.initials: HK
authors.lastname: Mao
authors.forename: A P
authors.initials: AP
authors.lastname: Jephcoat
authors.forename: R J
authors.initials: RJ
authors.lastname: Hemley
authors.forename: L W
authors.initials: LW
authors.lastname: Finger
authors.forename: C S
authors.initials: CS
authors.lastname: Zha
authors.forename: R M
authors.initials: RM
authors.lastname: Hazen
authors.forename: D E
authors.initials: DE
authors.lastname: Cox