High-pressure single crystal X-ray diffraction and FT-IR observation of natural chondrodite and synthetic OH-chondrodite
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Accession number;04A0874343
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| Title;High-pressure single crystal X-ray diffraction and FT-IR observation of natural chondrodite and synthetic OH-chondrodite |
| Author;
KURIBAYASHI T
(Tohoku Univ., Sendai, Jpn)
KAGI H
(Univ. Tokyo, Tokyo, Jpn)
TANAKA M
(Kek, Tsukuba, Jpn)
AKIZUKI M
(Tohoku Univ., Sendai, Jpn)
KUDOH Y
(Tohoku Univ., Sendai, Jpn)
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Journal Title;J Mineral Petrol Sci
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Journal Code:G0150B
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ISSN:1345-6296
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VOL.99;NO.3;PAGE.118-129(2004)
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| Figure&Table&Reference;FIG.6, TBL.4, REF.50 |
| Pub. Country;Japan |
| Language;English |
| Abstract;High-pressure single crystal X-ray diffraction studies of a natural chondrodite, Mg4.76Fe0.22Ti0.02Si1.99O8 (OH1.26F0.74), and a synthetic OH-chondrodite, Mg4.98Si2.01H2.00O10, were performed using a diamond anvil cell (DAC) up to 7.3 and 5.9GPa, respectively and at room temperature. FT-IR spectra of the natural chondrodite under high-pressure conditions up to 9.9GPa was also observed using a DAC. The axial linear compressibilities of these samples are calculated as .BETA.a=1.69(4)*10-3, .BETA.b=2.98(4)*10-3 and .BETA.c=2.74(5)*10-3(GPa-1) for the natural chondrodite and .BETA.2=2.11(18)*10-3, .BETA.b=2,83(18)*10-3 and .BETA.c=3.04(38)*10-3(GPa-1) for the synthetic OH-chondrodite. The isothermal bulk moduli of these samples were calculated as KT=124.1(4)GPa for the natural chondrodite and KT=117(2)GPa for the OH-chondrodite, by using the Birch-Murnaghan equation of state assuming K'=4. The bulk moduli of total void space in each sample, assuming K'=4, were calculated to be K.SQU.=116(2)GPa for the natural chondrodite and K.SQU.=113(4)GPa for the OH-chondrodite. The plots of bulk modulus versus the summation of the filling-factor of polyhedral sites show a good correlation between the humite minerals. This relationship can be explained by the replacement of 4O2-+Si4+.DARRLR.4(F,OH)-+.SQU. generated in the humite homologous series. In the FT-IR spectra of the natural chondrodite, four OH-stretching vibrational peaks were observed at 3688, 3566, 3558 and 3383cm-1 under ambient conditions. The pressure dependences of the frequency of these peaks up to 9.9GPa are 2.8(3), 3.9(3), 4.0(3) and -2.1(2)(cm-1GPa-1), respectively. With increasing pressure up to 9.9GPa, the 3383cm-1 peak shifts to lower-frequency positions, whereas the other peaks shift to higher-frequency positions. The shortening of the O5...O5 distance, which is not the shared edge between M3 octahedra, related to hydrogen bonding with increasing pressure causes the negative pressure-dependence of the 3383cm-1 peak.... (author abst.) |
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