Metallic ferroelectricity induced by anisotropic unscreened coulomb   interaction in LiOsO3
  As the first well-documented example of the ferroelectric metal, LiOsO3 has received extensive research attention recently. Using density-functional calculations, we perform a systematic study for LiOsO3. We address the controversy about the depth of the double well in the potential surface, and propose that the ferroelectric transition is order-disorder like. Moreover, we unambiguously demonstrate that the electric screening in this compound is highly anisotropic, and there is still unscreened dipole-dipole interaction in one special direction which results in the long range ferroelectric order despite the metallic nature of LiOsO3. 
H. M. Liu, Y. P. Du, Y. L. Xie, J. -M. Liu, Chun-Gang Duan and   Xiangang Wan
cond-mat.mtrl-sci