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Raman spectroscopic study of PbCO3 at high pressures and temperatures |
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| Authors: | Robert Minch Leonid Dubrovinsky Alexandr Kurnosov Lars Ehm Karsten Knorr Wulf Depmeier |
| Institution: | 1. Institut fuer Geowissenschaften, CAU zu Kiel, Olshausenstr. 40, 24098, Kiel, Germany 2. Bayerisches Geoinstitut, Universitaet Bayreuth, 95220, Bayreuth, Germany 3. Mineral Physics Institute, Stony Brook University, 255 Earth and Space Science Building, Stony Brook, NY, 11794-2100, USA 4. Brookhaven National Laboratory, National Synchrotron Light Source, 75 Brookhaven Avenue, Upton, NY, 11973-5000, USA 5. Bruker AXS-GmbH, XRD Marketing, Oestliche Rheinbrueckenstr. 49, 76187, Karlsruhe, Germany |
| Abstract: | Cerussite (PbCO3) has been investigated by high-pressure and high-temperature Raman spectroscopy up to pressures of 17.2 GPa and temperatures of 723 K. Two pressure induced phase transitions were observed at about 8.0(2) and 16.0(2) GPa, respectively. The post-aragonite transition (PbCO3-II) at 8.0(2) GPa is accompanied by softening of the v 2-out-of-plane mode of the CO 3 2? group and disappearance of the B1g (v 4-in-plane band of the CO 3 2? group) mode. Stronger shifts of the carbonate group modes after the phase transition suggest that the new structure is more compressible. The formation of a second high-pressure polymorph begins at about 10 GPa. It is accompanied by the occurrence of three new bands at different pressures and splitting of the v 1-symmetric C–O stretching mode of the CO 3 2? group. The transitions are reversible on pressure release. A semi-quantitative phase diagram for PbCO3 as a function of pressure and temperature is proposed. |
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