  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.
