An Unusual Phase Transition Driven by Vibrational Entropy Changes in a Hybrid Organic–Inorganic Perovskite. (20th June 2018)

• Record Type: Journal Article
• Authors: Wei, Wenjuan; Li, Wei; Butler, Keith T.; Feng, Guoqiang; Howard, Christopher J.; Carpenter, Michael A.; Lu, Peixiang; Walsh, Aron; Cheetham, Anthony K.
• Is Part Of: Angewandte Chemie. Volume 130:Number 29(2018)
• Page Start: 9070
• Page End: 9074
• Publication Date: 2018-06-20
• Subjects: Ab-initio-Rechnungen -- Gitterdynamik -- Organisch-anorganische Hybridperowskite -- Phasenübergänge -- Schwingungsentropie; Chemistry -- Periodicals; 540
• DOI: 10.1002/ange.201803176
• Languages: English
• ISSNs: 0044-8249

Abstract

Abstract: The driving forces for the phase transitions of ABX3 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.