Crystal structures of high-pressure phases in the alumina-water system: I. Single crystal X-ray diffraction and molecular dynamics simulation ofη-Al(OH)3

Abstract

The high-pressure phase of gibbsite has been studied byin situsingle crystal X-ray diffraction method and molecular dynamics (MD) simulation at 3.0 GPa. The crystal structure of the high-pressure phase,η-Al(OH)3, was successfully determined by direct methods based on the intensities of X-ray diffraction. The space group and lattice constants forη-Al(OH)3areP21/b11 (#14),a= 8.612(3) Å,b= 5.013(2) Å,c= 9.194(5) Å andα= 90.34(6)°, respectively. The crystal structure ofη-Al(OH)3consists of an Al octahedral layer, and the layers are connected via H-bonds. The mechanism of the phase transition from gibbsite toη-Al(OH)3is also discussed in the context of previously reported powder X-ray diffraction data.