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Figure 3
Determination of the MA and Ne positions in the crystal structure of MAPbI3 at selected pressures. Projections of the relevant fragments of the structure onto the ac plane are in (a) and (c). Small dots indicate I atoms in the plane for which the difference electron density maps are shown in (b) and (d) with positive (red) and negative (blue) areas. (b) The maps were calculated using only Pb and I atoms. The maxima of the difference electron densities are identified with MA cations (dark-blue circles) and Ne atoms (cyan circles). The density varies: from −0.32 to 1.58 e Å−3 for the released crystal at P = 1 atm; from 0.20 to 0.41 e Å−3 for the pristine crystal at P = 1 atm; from −1.44 to 1.97 e Å−3 for P = 0.69 GPa; from −1.13 to 1.86 e Å−3 for P = 20.27 GPa. (d) The residual electron density maps were calculated using all atoms of the structure. The residual electron density varies: from −0.3 to 0.51 e Å−3 atm for the released crystal at P = 1; from −0.27 to 0.23 e Å−3 for the pristine crystal at P = 1 atm; from −1.06 to 1.07 e Å−3 for P = 0.69 GPa; from −0.54 to 0.56 e Å−3 for P = 20.27 GPa. |