Crystal structure of BaFe 2 Se 3 as a function of temperature and pressure: phase transition phenomena and high-order expansion of Landau potential
V. Svitlyk , D. Chernyshov , E. V. Pomjakushina , Anna Krztoń-Maziopa , K. Conder , V. Yu. Pomjakushin , R Pöttgen , V. Dmitriev
AbstractBaFe 2 Se 3 (Pnma , CsAg 2 I 3 -type structure), recently assumed to show superconductivity at ∼11 K, exhibits a pressure-dependent structural transition to the CsCu 2 Cl 3 -type structure ( Cmcm space group) around 60 kbar, as evidenced from pressure-dependent synchrotron powder diffraction data. Temperature-dependent synchrotron powder diffraction data indicate an evolution of the room-temperature BaFe 2 Se 3 structure towards a high-symmetry CsCu 2 Cl 3 form upon heating. Around 425 K BaFe 2 Se 3 undergoes a reversible, first-order isostructural transition, which is supported by the differential scanning calorimetry data. The temperature-dependent structural changes occur in two stages, as determined by the alignment of the FeSe 4 tetrahedra and corresponding adjustments of the positions of Ba atoms. On further heating, a second-order phase transformation into the C mcm structure is observed at 660 K. A rather unusual combination of isostructural and second-order phase transformations is parameterized within phenomenological theory assuming high-order expansion of the Landau potential. A generic phase diagram mapping observed structures is proposed on the basis of the parameterization.
|Journal series||Journal of Physics-Condensed Matter, ISSN 0953-8984|
|Publication size in sheets||15770.15|
|Score|| = 30.0, 01-02-2020, ArticleFromJournal|
= 30.0, 01-02-2020, ArticleFromJournal
|Publication indicators||= 13; = 11; : 2013 = 1.035; : 2013 = 2.223 (2) - 2013=2.335 (5)|
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