First evidence of <i>P</i>2<i>1/n</i> to <i>P</i>2<i>1/c</i> structural transformation in pyroxene-type LiAlGe₂O₆ under high-pressure conditions

Autor(en)

Fabrizio Nestola, Andreas Artac, Thomas Pippinger, Ronald Miletich-Pawliczek, Luciano Secco, Sula Milani

Abstrakt

The high-pressure behavior of the pyroxene-type compd. LiAlGe2O6, the unique representative of a P21/n-pyroxene, was investigated by in-situ X-ray diffraction and Raman spectroscopy on single-crystal samples hydrostatically pressurized in a diamond-anvil cell. The structure was found to undergo a first-order phase transition on compression, with a crit. transition at 5.23±0.02 GPa. Together with a strong vol. discontinuity of -V/V0=-4.1% the transition shows a remarkable hysteresis loop over at least 0.70 GPa pressure interval. The bulk modulus of the low- and high-pressure polymorphs corresponds to K0=114(1) and 123(2) GPa, resp., as described by a 2nd order Birch-Murnaghan equation of state. Based on the systematic extinctions the transition was identified as a P21/n-to-P21/c transformation. The mechanism of structural transformation was identified to be controlled by the stereochem. of the Li atoms at the M2 site, which changes its coordination no. from 5 to 6. The formation of new Li-O bonds involves the co-operative folding of Ge2O6-chains, which explains the anisotropy of axial elasticities and the spontaneous strain across the transformation. Simultaneously the distortion correction of AlO6 units assocd. with the transition further explains the preference of the P21/c structure under pressure.

Organisation(en)

Institut für Mineralogie und Kristallographie

Externe Organisation(en)

Università degli Studi di Padova, Universität Bayreuth

Journal

Journal of Solid State Chemistry

Band

228

Seiten

250-257

Anzahl der Seiten

8

ISSN

0022-4596

DOI

https://doi.org/10.1016/j.jssc.2015.05.005

Publikationsdatum

06-2015

Peer-reviewed

Ja

ÖFOS 2012

104011 Materialchemie, 105113 Kristallographie

Schlagwörter

ASJC Scopus Sachgebiete

Electronic, Optical and Magnetic Materials, Condensed Matter Physics, Ceramics and Composites, Materials Chemistry, Inorganic Chemistry, Physical and Theoretical Chemistry

Link zum Portal

https://ucrisportal.univie.ac.at/de/publications/first-evidence-of-p21n-to-p21c-structural-transformation-in-pyroxenetype-lialge2o6-under-highpressure-conditions(e71e3b3d-30cc-45dc-9096-08b943f01819).html