Fig. 4: Density functional theory (DFT) calculations of (4,4-DFPD)2GeBr4. | Nature Communications

Fig. 4: Density functional theory (DFT) calculations of (4,4-DFPD)2GeBr4.

From: Lone pair expression in fluorinated two-dimensional hybrid perovskite enables multiaxial ferroelectricity and nonlinear optical response

Fig. 4: Density functional theory (DFT) calculations of (4,4-DFPD)2GeBr4.

a, b Packing view of 4,4-DFPD cations at ferroelectric configuration (λ = 1) and paraelectric configuration (λ = 0). θ1 and θ2 represent the rotation angle of 4,4-DFPD cations in plane that parallel and perpendicular to the 2D layer for modeling dynamic path. c, d 2D [GeBr4]2− skeleton at λ = 1 and λ = 0. e, f Evolution of polarization along crystallographic a and c-axis as a function of the dynamic path connecting the λ = 1 to λ = 0. g, h The 2D inorganic layer transform from the ferroelectric state to the paraelectric state with organic cations are kept in the ferroelectric state. Lone pairs electrons located in the 2D layer enhance the polarization along the crystallographic a-axis.

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