Origin of the ferroelectricity in hydrogen-bonded ferroelectrics [MIICl3(H-MPPA)] (M=Co and Zn) from first-principles study

Electronic structure, spontaneous polarization and dielectric properties of the hydrogen-bonded ferroelectrics [MIICl3(H-MPPA)] (M=Co and Zn) are investigated based on density functional theory (DFT). Their energy band structures reveal they are insulators with wide band gaps, and there is evidence of hybridization between Zn, Co 3d and Cl 2p states. The large spontaneous polarization means that the two compounds are promising ferroelectrics. In addition, the origin of the spontaneous polarization of the two compounds is found to result from the identical orientation of the symmetric NH⋯Cl hydrogen bonds.