Acta Crystallographica Section B

Structural Science

Volume 57, Part 4 (August 2001)

short communications

Acta Cryst. (2001). B57, 599-601 [ doi:10.1107/S0108768101006164 ]

Ferroelectric-paraelectric phase transitions with no group-supergroup relation between the space groups of both phases?

E. Kroumova, M. I. Aroyo, J. M. Pérez-Mato and R. Hundt

Abstract: The structures of Sr₃(FeF₆)₂, [beta] -NbO₂, TlBO₂ and CrOF₃, previously reported as possible ferroelectrics with no group-supergroup relation between the ferroelectric and the paraelectric symmetries, have been carefully studied. We could not confirm any structural pseudosymmetry with respect to a space group which is not a supergroup of their room-temperature polar space group. In all cases, pseudosymmetry was indeed detected, but only for non-polar supergroups of the actual space groups of the structures. In this sense, the four compounds are possible ferroelectrics, but fulfilling the usual group-supergroup relation between the phase symmetries.

Keywords: ferroelastic-paraelectric phase transitions; group-supergroup relation.