title: Structural refinement of the high-pressure phase of aluminum trihydroxide: in-situ high-pressure angle dispersive synchrotron X-ray diffraction and theoretical studies.
abstract: In-situ high-pressure synchrotron angle-dispersive X-ray diffraction for gibbsite (aluminum trihydroxide) was performed at room temperature up to 20 GPa. A pressure-induced phase transition was observed at 2.6 GPa. The new high-pressure phase can be recovered at ambient pressure. Rietveld refinement shows that the new phase of Al(OH)(3) has an orthorhombic structure, spacegroup Pbca, and the lattice parameters at ambient condition are a = 868.57(5) pm, b = 505.21(4) pm, c = 949.54(6) pm, V = 416.67(6) x 10(6) pm(3) with Z = 8. The compressibility of gibbsite and the high-pressure polymorph was analyzed, and their bulk moduli were estimated as 49.8 +/- 1.8 and 81.0 +/- 5.2 GPa, respectively. First-principles calculations of the high-pressure phase were performed to determine the hydrogen positions and to confirm the structural stability of the new phase.
authors.affiliation: HPCAT, Advanced Photon Source, Building 434E, Argonne National Laboratory, Argonne, Illinois 60439-4803, USA. hliu@hpcat.aps.anl.gov
authors.forename: Haozhe
authors.initials: H
authors.lastname: Liu
authors.forename: John S
authors.initials: JS
authors.lastname: Tse
authors.forename: Jingzhu
authors.initials: J
authors.lastname: Hu
authors.forename: Zhenxian
authors.initials: Z
authors.lastname: Liu
authors.forename: Luhong
authors.initials: L
authors.lastname: Wang
authors.forename: Jiuhua
authors.initials: J
authors.lastname: Chen
authors.forename: Don J
authors.initials: DJ
authors.lastname: Weidner
authors.forename: Yue
authors.initials: Y
authors.lastname: Meng
authors.forename: Daniel
authors.initials: D
authors.lastname: Häusermann
authors.forename: Ho-Kwang
authors.initials: HK
authors.lastname: Mao
mesh_terms: D000536:Aluminum Hydroxide / Q000737:chemistry*; D011312:Pressure; D017550:Spectroscopy, Fourier Transform Infrared; D013059:Spectrum Analysis, Raman; D013500:Surface Tension; D014961:X-Ray Diffraction
chemical_list: D000536:Aluminum Hydroxide