1. An Unusual Phase Transition Driven by Vibrational Entropy Changes in a Hybrid Organic–Inorganic Perovskite.
- Author
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Wei, Wenjuan, Li, Wei, Butler, Keith T., Feng, Guoqiang, Howard, Christopher J., Carpenter, Michael A., Lu, Peixiang, Walsh, Aron, and Cheetham, Anthony K.
- Subjects
MAGNETOCALORIC effects ,PHASE transitions ,FIRST-order phase transitions ,MAGNETIC entropy ,LATTICE dynamics ,PEROVSKITE ,ENTROPY ,ATOMIC structure - Abstract
Abstract: The driving forces for the phase transitions of ABX
3 hybrid organic–inorganic perovskites have been limited to the octahedral tilting, order–disorder, and displacement. Now, a complex structural phase transition has been explored in a HOIP, [CH3 NH3 ][Mn(N3 )3 ], based on structural characterizations and ab initio lattice dynamics calculations. This unusual first‐order phase transition between two ordered phases at about 265 K is primarily driven by changes in the collective atomic vibrations of the whole lattice, along with concurrent molecular displacements and an unusual octahedral tilting. A significant entropy difference (4.35 J K−1 mol−1 ) is observed between the low‐ and high‐temperature structures induced by such atomic vibrations, which plays a main role in driving the transition. This finding offers an alternative pathway for designing new ferroic phase transitions and related physical properties in HOIPs and other hybrid crystals. [ABSTRACT FROM AUTHOR]- Published
- 2018
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