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An infrared spectroscopic study of the OH stretching frequencies of talc and 10-Å phase to 10 GPa

Stephen A. Parry^1,*, Alison R. Pawley^1,, Ray L. Jones² and Simon M. Clark³

¹ School of Earth, Atmospheric and Environmental Sciences, University of Manchester, Manchester, M13 9PL, U.K.
² Daresbury Laboratory, Daresbury, Cheshire WA4 4AD, U.K.
³ Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, California 94720, U.S.A.

Correspondence: E-mail: alison.pawley{at}manchester.ac.uk

The effects of pressure on the OH stretching frequencies of natural talc and two samples of synthetic 10-Å phase have been measured using a diamond-anvil cell and a synchrotron infrared source. The 10-Å phase was synthesized at 6.0–6.5 GPa, 600 °C for 46 hours (sample 10Å-46) and 160 hours (10Å-160). Spectra were collected up to 9.0 GPa (talc), 9.9 GPa (10Å-46), and 9.6 GPa (10Å-160). The OH stretching vibration of Mg₃OH groups in talc occurs at 3677 cm^–1 at ambient pressure, and increases linearly with pressure at 0.97(2) cm^–1 GPa^–1. The same vibration occurs in 10-Å phase, but shows negligible pressure shift up to 2 GPa, above which the frequency increases linearly to the maximum pressure studied, at a rate of 0.96(3) cm^–1 GPa^–1 (10Å-46) and 0.87(3) cm^–1 GPa^–1 (10Å-160). Two other prominent bands in the 10-Å phase spectrum are suggested to be due to stretching of interlayer H₂O, hydrogen-bonded to the nearest tetrahedral sheet. These bands also show little change over the first 2 GPa of compression, as most of the compression of the structure is taken up by closing non-hydrogen bonded gaps between interlayer H₂O and tetrahedral sheets. Between 2 and 4 GPa, changes in band intensities suggest a rearrangement of the interlayer H₂O.

Key Words: Talc • 10-Å phase • high-pressure studies • IR spectroscopy

This article has been cited by other articles:

				A.E. Gleason, S.A. Parry, A.R. Pawley, R. Jeanloz, and S.M. Clark Pressure-temperature studies of talc plus water using X-ray diffraction American Mineralogist, July 1, 2008; 93(7): 1043 - 1050. [Abstract] [Full Text] [PDF]