Related Experiment Video
Updated: May 9, 2026

Synthesis and Microdiffraction at Extreme Pressures and Temperatures
Published on: October 7, 2013
Crystal structure of BaFe2Se3 as a function of temperature and pressure: phase transition phenomena and high-order
V Svitlyk1, D Chernyshov, E Pomjakushina
1Institut für Anorganische und Analytische Chemie, WWU Münster, Münster, Germany. svitlyk@esrf.fr
Abstract:
BaFe2Se3 (Pnma, CsAg2I3-type structure), recently assumed to show superconductivity at ~11 K, exhibits a pressure-dependent structural transition to the CsCu2Cl3-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 BaFe2Se3 structure towards a high-symmetry CsCu2Cl3 form upon heating. Around 425 K BaFe2Se3 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 FeSe4 tetrahedra and corresponding adjustments of the positions of Ba atoms. On further heating, a second-order phase transformation into the Cmcm 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.
Related Concept Videos
Phase Diagram
Phase Diagram
Phase Diagrams
Solid–Solid Solutions
Crystal Field Theory - Octahedral Complexes
To explain the observed behavior of transition metal complexes (such as colors), a model involving electrostatic interactions between the electrons from the ligands and the electrons in the unhybridized d orbitals of the central metal atom has been developed. This electrostatic model is crystal field theory (CFT). It helps to understand, interpret, and predict the colors, magnetic behavior, and some structures of coordination compounds of transition metals.
CFT focuses on...
Phase Changes
A substance melts or freezes at a temperature called its melting point and boils or condenses at its boiling point. These temperatures depend on pressure. High pressure favors the denser form of the substance, so typically, high pressure...

