TY  - JOUR
AU  - Kotla, Surya Rohith
AU  - Ramakrishnan, Sitaram
AU  - Schaller, Achim M.
AU  - Rekis, Toms
AU  - Eisele, Claudio
AU  - Bao, Jin-Ke
AU  - Noohinejad, Leila
AU  - de Laitre, Geoffroy
AU  - de Boissieu, Marc
AU  - van Smaalen, Sander
TI  - Deciphering the commensurately modulated monoclinic phase of Rb<sub>2</sub>ZnCl<sub>4</sub> at low temperatures
JO  - Journal of solid state chemistry
VL  - 345
SN  - 0022-4596
CY  - Orlando, Fla.
PB  - Academic Press
M1  - PUBDB-2025-01658
SP  - 125226
PY  - 2025
AB  - The ferroelectric phase III of Rb<sub>2</sub>ZnCl<sub>4</sub> is stable below T<sub>c</sub> = 192 K. It is known to be a threefold superstructure of the centrosymmetric high-temperature structure, with space group P2<sub>1</sub> cn. Below T<sub>L</sub> = 70 K, phase IV exists as a sixfold superstructure. We report the crystal structure of phase IV with monoclinic symmetry Cc (b unique), while a structure model with symmetry Pn (c unique) leads to an almost equally good, yet significantly worse fit to the diffraction data. Employing the superspace approach to these commensurately modulated structures results in modulation waves that follow the two-dimensional irreducible representation T<sub>1</sub> of P2<sub>1</sub> cn, albeit with different order parameter directions defining Cc and Pn symmetries, consistent with the literature. Standard tools of crystal-chemical analysis indicate that the sixfold superstructure is more stable than the threefold superstructure of phase III. However, crystal-chemical arguments cannot distinguish between the correct superstructure model with space group Cc (b unique) and the incorrect superstructure model with symmetry Pn (c unique) for phase IV. New crystal chemical tools are required, in order to attain a meaningful understanding of superstructure formation.
LB  - PUB:(DE-HGF)16
UR  - <Go to ISI:>//WOS:001425621500001
DO  - DOI:10.1016/j.jssc.2025.125226
UR  - https://bib-pubdb1.desy.de/record/627883
ER  -