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

• The metal-organic coordination (MOC) has presented various properties because of its hybrid character, however ferroelectric MOC materials are scarce.
• The new hydrogen bonds ferroelectric [MIICl3(H-MPPA)] (M=Co and Zn) provide a new avenue to explore novel MOF-type ferroelectrics.
• For the new hydrogen-bonded ferroelectric, it is valuable to investigate the origin of the ferroelectricity.
• By investigating the dielectric properties, we find that the two compounds should be high performance dielectric materials.

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.