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High-pressure phase transformation in LiFeGe (sub 2) O (sub 6) pyroxene

Fabrizio Nestola, Guenther J. Redhammer, Martha G. Pamato, Luciano Secco and Alberto Dal Negro
High-pressure phase transformation in LiFeGe (sub 2) O (sub 6) pyroxene
American Mineralogist (April 2009) 94 (4): 616-621


A synthetic pyroxene with composition LiFeGe (sub 2) O (sub 6) and space group P2 (sub 1) /c at ambient conditions was investigated by single-crystal X-ray diffraction using a diamond anvil cell. The unit-cell parameters and crystal structure were determined at eight different pressures up to 8.7 GPa. Between 4.16 and 4.83 GPa, the sample shows a strongly first-order phase transition as indicated by a drastic drop in a, c, beta , and unit-cell volume. The transition is marked by the disappearance of b-type reflections (h+k=odd) forbidden in a C-centered lattice. The volume bulk modulus of the P2 (sub 1) /c phase is estimated to be 110 GPa as compared to 147 GPa of the C2/c one. The crystal structure evolution as a function of pressure is mainly influenced by the kinking of tetrahedral chains; the A and B non-symmetry equivalent chains of the P2 (sub 1) /c phase undergo strong deformations up to 4.16 GPa (A chain approximately 2%, B chain approximately 5.3%). At the transition, the two chains become symmetry equivalent and the single tetrahedral chain of the C2/c phase shows only minor deformations with pressure (approximately 1.9%) due to its already strong kinking (approximately 130 degrees ). Such behavior is the main reason for the strong difference in compressibility between the low- and high-symmetry forms.

ISSN: 0003-004X
EISSN: 1945-3027
Serial Title: American Mineralogist
Serial Volume: 94
Serial Issue: 4
Title: High-pressure phase transformation in LiFeGe (sub 2) O (sub 6) pyroxene
Affiliation: Universita di Padova, Dipartimento di Geoscienze, Padua, Italy
Pages: 616-621
Published: 200904
Text Language: English
Publisher: Mineralogical Society of America, Washington, DC, United States
References: 19
Accession Number: 2009-042459
Categories: Geophysics of minerals and rocks
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 3 tables
Secondary Affiliation: University of Salzburg, AUT, Austria
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Abstract, copyright, Mineralogical Society of America. Reference includes data from GeoScienceWorld, Alexandria, VA, United States
Update Code: 200923
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