  Two-dimensional sliding ferroelectrics, with their unique stacking degrees of
freedom, offer a different approach to manipulate polarization by interlayer
sliding. Bending sliding ferroelectrics inevitably leads to interlayer sliding
motion, thus altering stacking orders and polarization properties. Here, by
using machine-learning force field, we investigate the effects of bending
deformation on geometries, stackings, energies, and polarizations in sliding
ferroelectric bilayer h-BN and 3R-MoS2. We predict that bent ferroelectric
bilayer forms irreversible kinks instead of arc when the bending angle exceeds
a critical value. We demonstrate that the kinks originate from the competition
between bending energy and interlayer van der Waals energy. The kink contains a
ferroelectric domain wall that reverses the polarization, effectively inducing
a flexoelectric effect. We term this phenomenon "sliding flexoelectricity" to
distinguish it from conventional strain-gradient-induced flexoelectricity.
