High-pressure phase transition in brucite, Mg(OH)2

Publication

Reference: Duffy Thomas S., Meade Charles, Fei Yingwei, Mao Ho-Kwang, Hemley Russell J. (1995). High-pressure phase transition in brucite, Mg(OH)2. Am. Mineral., 80, 222 - 230.

Names

Title: High-pressure phase transition in brucite, Mg(OH)2
Abstract: Brucite, Mg(OH)2, was investigated by Raman spectroscopy to pressures of 36.6 GPa under nonhydrostatic conditions and to 19.7 GPa under quasi-hydrostatic conditions. Several new Raman lines are first observed at 4 GPa, demonstrating the existence of a high-pressure structural change. One of the new lines grows over a broad pressure interval, and this growth can be explained by a resonant interaction with the Eg translational mode. Raman data are compared with recent infrared spectroscopy, X-ray diffraction, and neutron diffraction studies of brucite. The structural change is likely to involve displacement or disordering of the H atoms, consistent with neutron diffraction results. The Raman-active O-H stretching vibration in brucite decreases with pressure at the rate of ∼7 cm−1/ GPa, larger than the pressure dependence of the infrared-active stretching vibration by more than a factor of ten. The primary differences in the Raman spectra of Mg(OH)2 and Ca(OH)2 are that the O-H vibrational frequencies in Mg(OH)2 vary linearly with pressure, and the O-H stretching vibration band width increases with pressure at a rate that is an order of magnitude lower for Mg(OH)2 than for Ca(OH)2.
Keywords: brucite, oxides, high pressure, phase equilibria
Content: sample, phase, band list data

Doi

10.2138/am-1995-3-403

Identifiers

Experiment/Spectra