Ferroelectric--paraelectric phase transitions with no group--supergroup relation between the space groups of both phases?
The structures of Sr(3)(FeF(6))(2), beta-NbO(2), TlBO(2) and CrOF(3), 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.
Kroumova
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Departamento de Física de la Materia Condensada, Universidad del País Vasco, Apdo 644, 48080 Bilbao, Spain. wmbbokre@lg.ehu.es
Aroyo
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Pérez-Mato
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JM
Hundt
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