Fig.1

DSC curves of (a) non-deuterated MAPbCl3 (CH3NH3PbCl3) and (b) deuterated MAPbCl3 (CD3NH3PbCl3) measured from 150.0 K to 190.0 K

Fig.2

Simulated 2H NMR spectra showing the effect of the rotation along the Cn bond. The Cn denotes the rotation axis and θ = 70˚ denotes the open angle between the C-D bond and Cn. In the simulation, the speed of rotation is set to fast limit. Some atoms in the MA cation are omitted for clarity

Fig.3

(a) The motion model Ⅱ of MA cation; (b) Simulated 2H NMR spectra showing the effect of the wobbling motion in Fig. (a). In the simulation, σ increases from 0˚ to 20˚. The speeds of the rotation along the C-N bond and wobbling motion are both set to fast limit. Some atoms in the MA cation are omitted for clarity

Fig.4

(a) The motion model Ⅲ of MA cation; (b) Simulated 2H NMR spectra based on the motion model Ⅲ. In the simulation, Ω is set to 1 000 kHz and θ varies from 50˚ to 60˚; (c) Simulated 2H NMR spectra based on the motion model Ⅲ. In the simulation, θ is set to 54.7˚ and Ω varies from 100 kHz to 2 000 kHz. Some atoms in the MA cation are omitted for clarity

Fig.5

(a) The motion model Ⅳ of MA cation; (b) Simulated 2H NMR spectra based on the motion model Ⅳ. In the simulation, Ω is set to 80 kHz and θ varies from 50˚ to 60˚; (c) Simulated 2H NMR spectra based on the motion model Ⅳ. In the simulation, θ is set to 54.7˚ and Ω varies from 50 kHz to 110 kHz. Some atoms in the MA cation are omitted for clarity

Fig.6

Experimental (black line) and simulated (gray line) solid state 2H NMR spectra of deuterated MAPbCl3 at 148.0 K

Fig.7

Experimental (black line) and simulated (gray line) solid state 2H NMR spectra of deuterated MAPbCl3 from 172.0 K to 176.0 K

Fig.8

(a) Simulated solid state 2H NMR spectra (176.0 K) based on the motion model Ⅱ (σ = 15˚), Ⅲ (θ = 43˚, Ω = 2 000 kHz) and Ⅳ (θ = 54.7˚, Ω = 80 kHz) of MA cation; (b) Experimental (black line) and simulated (gray line) solid state 2H NMR spectra of deuterated MAPbCl3 at 176.0 K. At this temperature, the spectra can be simulated by superimposing three curves in Fig. (a) proportionally

Fig.9

The proportion variations of the simulated 2H NMR spectra based on the three motion models as a function of temperature (172.0~176.0 K)

Fig.10

Experimental (black line) and simulated (gray line) solid state 2H NMR spectra of deuterated MAPbCl3 from 177.0 K to 186.0 K

Fig.11

(a) Simulated solid state 2H NMR spectra (180.0 K) based on the motion model Ⅲ (θ = 54.7˚, Ω = 3 000 kHz) and Ⅳ (θ = 54.7˚, Ω = 82 kHz) of MA cation; (b) Experimental (black line) and simulated (gray line) solid state 2H NMR spectra of deuterated MAPbCl3 at 180.0 K. At this temperature, the spectra can be simulated by superimposing two curves in Fig. (a) proportionally

Fig.12

(a) Simulated solid state 2H NMR spectra (184.0 K) for the three motion models of MA cation; (b) Experimental (black line) and simulated (gray line) solid state 2H NMR spectra of deuterated MAPbCl3 at 184.0 K. At this temperature, the spectra can be simulated by superimposing three curves in Fig. (a)

Fig.13

Distribution diagrams of various MA cation motion components in different phases