Metallic ferroelectricity induced by anisotropic unscreened Coulomb interaction in LiOsO3

As the first experimentally confirmed ferroelectric metal, LiOsO3 has received extensive research attention recently. Using density-functional calculations, we perform a systematic study on the origin of the metallic ferroelectricity in LiOsO3. We confirm that the ferroelectric transition in this compound is order-disorder-like. By doing electron screening analysis, we unambiguously demonstrate that the long-range ferroelectric order in LiOsO3 results from the incomplete screening of the dipole-dipole interaction along the nearest-neighboring Li-Li chain direction. We conclude that highly anisotropic screening and local dipole-dipole interactions are the two most important keys to form LiOsO3-type metallic ferroelectricity.