Synthesis, crystal structure, and phase relations of AlSiO 3 OH, a high-pressure hydrous phase
1998; Mineralogical Society of America; Volume: 83; Issue: 7-8 Linguagem: Inglês
10.2138/am-1998-7-820
ISSN1945-3027
AutoresMax W. Schmidt, L. W. Finger, R. J. Angel, Robert E. Dinnebier,
Tópico(s)X-ray Diffraction in Crystallography
ResumoPhase egg, first described by Eggleton et al. (1978), was synthesized and its composition determined to be AlSiO 3 OH.The crystal structure of AlSiO 3 OH, including the position of the hydrogen, has been solved and refined from high-resolution X-ray powder diffraction.The resulting lattice constants are a ϭ 7.14409(2) A ˚, b ϭ 4.33462(1) A ˚, c ϭ 6.95253(2)A ˚, and  ϭ 98.396(1)Њ.The space group is P2 1 /n; Z ϭ 4, V 0 ϭ 212.99(1)A ˚3, and the zero pressure density is 3.74 g/cm 3 .This phase, which has features in common with the stishovite structure, occurs above 11 GPa and 700 ЊC.AlSiO 3 OH forms from topaz-OH with increasing pressure and persists to more than 17.7 GPa and 1300 ЊC.From a Schreinemaker analysis, we predicted that phase egg decomposes with pressure to an unknown, possibly hydrous aluminosilicate.Potentially, phase egg could replace topaz-OH or kyanite in subducted crustal bulk compositions and may transport some water into the deep Earth.
Referência(s)