Fig. 4: Phonon dispersion and IR active modes.

a The theoretical calculated room-temperature phonon band structure and b IR absorption spectrum of cubic MAPbBr3. Real-space visualization of vibration phonon modes at c 0.59~0.74, d 1.18~1.36, and e 1.8~1.83 THz. Grey, brown, purple, orange, and pink balls denote Pb, Br, C, N, and H atoms, and the blue and red arrows represent the eigenvectors corresponding to the phonon modes.