THE FORMATION OF HIGH-PRESSURE MODIFICATION OF HYDRATED TALC AT 450°C AND 4 GPa: IN SITU DIFFRACTION STUDY
A. Yu. Likhacheva1,2, S. V. Rashchenko3,4
1V.S.Sobolev Institute of Geology and Mineralogy SD RAS, Novosibirsk
2G.I. Budker Institute of Nuclear Physics SB RAS, Novosibirsk
3V.S. Sobolev Institute of Geology and Mineralogy SB RAS, Novosibirsk
4Novosibirsk State University, Novosibirsk
Keywords: тальк, 10 Г… фаза, высокая температура, высокое давление, дифрактометрия in situ, синхротронное излучение, talc, 10 Г… phase, high temperature, high pressure, powder diffraction in situ, synchrotron radiation
Abstract
The formation of the high-pressure hydrous phase Mg3Si4O10(OH)2xxH2O (10 Å phase) through the reaction ‘talc+water’ at 450°C and 4 GPa was studied using diamond anvil cell. The powder diffraction measurements in situ , performed at the Siberian Center of Synchrotron and Terahertz Radiation (SSTRC), were applied to refine the lattice parameters, atomic coordinates and the occupancy of interlayer H2O site in the structure of 10 Å phase at 450°C and 4 GPa. The lattice parameters are a = 5.234(1), b = 9.053(2), c = 10.87(1) Å, β = 99.2(1)о, and V = 508.5(6) Å3 (space group C2/m). The results of Rietveld refinement show the best fit for the trioctahedral mica structure with split position Ow of the interlayer H2O molecule. The half occupancy of the Ow site corresponds to one H2O molecule per formula unit.
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