Reinvestigation of the phase transition in ABW-type CsLiSO{sub 4}: Symmetry analysis and atomic distortions

Journal Article · Wed Jul 01 04:00:00 EDT 1998 · Journal of Solid State Chemistry

DOI:https://doi.org/10.1006/jssc.1998.7782· OSTI ID:651121

Kahlenberg, V ^[1]

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1. Univ. Bremen (Germany). Fachbereich Geowissenschaften

ABW-type CsLiSO{sub 4} shows a reversible structural phase transition at approximately 202 K. The transformation is translationengleich and the space group symmetries of the two different polymorphic forms are Pnma (phase I) and P{sub n}{sup 2{sub 1}}11 (phase II), respectively. The transition was reinvestigated using a group theoretical approach based on the published structural data of the two modifications. A combined rotation of the SO{sub 4} and LiO{sub 4}-tetrahedra was taken as the primary order parameter {eta} inducing the transformation. Projection operator calculations revealed that the transition can be associated with the irreducible representation {Gamma}{sub 3}{sup +} of Pnma. Displacements of the Li, S, and Cs ions as well as the occurrence of certain strain components are symmetry allowed, too, and can couple to {eta}. The global tilting pattern is compared with the rotational distortions observed in the transitions of ABW-type CsZnPO{sub 4}. A rigid-unit mode approach is proposed for the explanation of the transitions.

• OSTI ID: 651121
• Journal Information: Journal of Solid State Chemistry, Journal Name: Journal of Solid State Chemistry Journal Issue: 2 Vol. 138; ISSN 0022-4596; ISSN JSSCBI
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
ATOMIC DISPLACEMENTS
CESIUM SULFATES
CRYSTAL-PHASE TRANSFORMATIONS
LITHIUM SULFATES
ORDER PARAMETERS
SYMMETRY
TEMPERATURE RANGE 0065-0273 K
THEORETICAL DATA