- journal_title：American Mineralogist
- Contributor：Fabrizio Nestola ; Günther J. Redhammer ; Martha G. Pamato ; Luciano Secco ; Alberto Dal Negro
- Publisher：Mineralogical Society of America
- Date：2009-
- Format：text/html
- Language：en
- Identifier：10.2138/am.2009.3052
- journal_abbrev：American Mineralogist
- issn：0003-004X
- volume：94
- issue：4
- firstpage：616
- section：Articles
A synthetic pyroxene with composition LiFeGe2O6 and space group P21/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, β, 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 P21/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 P21/c phase undergo strong deformations up to 4.16 GPa (A chain ~2%, B chain ~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 (~1.9%) due to its already strong kinking (~130°). Such behavior is the main reason for the strong difference in compressibility between the low- and high-symmetry forms.