RETRACTED: PHASE-F, A NEW HYDROUS MAGNESIUM-SILICATE SYNTHESIZED AT 1000-DEGREES-C AND 17 GPA - CRYSTAL-STRUCTURE AND ESTIMATED BULK MODULUS (RETRACTED ARTICLE. SEE VOL 24, PG 601, 1997)

The structure of phase F, a non-stoichiometric hydrous silicate synthesized in a uniaxial, split-sphere, multi-anvil apparatus at conditions of 17 GPa and 1000 degrees C, has been solved and refined in space group P6(3)cm, using synchrotron X-ray data for a single crystal of a size 18 x 24 x 30 mu m. The composition and unit cell for phase F are Mg3.35Si5.51H7.26O18, a = 5.073(3) Angstrom c = 14.013(9) Angstrom, V = 312.3(5) Angstrom(3). The structure contains layers with many similarities to superhydrous phase B. The layers of oxygen atoms are stacked in the ABCBAC-type double cubic closest packing arrangement. The bulk modulus of phase F was estimated from the structural and compositional relationship to superhydrous phase B and periclase.