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, [CH3NH3][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.
Bibliographical noteFunding Information:
The authors acknowledge the funding support from the National Natural Science Foundation of China (Grant no.
21571072). W.W., G.F., W.L. and P.L. thank the Fundamental Research Funds for the Central Universities, HUST (Grant no. 2017KFXKJC002). W.L. is grateful to Prof. Song Gao for his illuminating suggestions.
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