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An Unusual Phase Transition Driven by Vibrational Entropy Changes in a Hybrid Organic–Inorganic Perovskite
Author(s) -
Wei Wenjuan,
Li Wei,
Butler Keith T.,
Feng Guoqiang,
Howard Christopher J.,
Carpenter Michael A.,
Lu Peixiang,
Walsh Aron,
Cheetham Anthony K.
Publication year - 2018
Publication title -
angewandte chemie
Language(s) - English
Resource type - Journals
eISSN - 1521-3757
pISSN - 0044-8249
DOI - 10.1002/ange.201803176
Subject(s) - phase transition , octahedron , ab initio , perovskite (structure) , chemistry , molecular vibration , ab initio quantum chemistry methods , chemical physics , lattice (music) , crystallography , materials science , crystal structure , condensed matter physics , molecule , physics , organic chemistry , acoustics
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, [CH 3 NH 3 ][Mn(N 3 ) 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.