Ice XI: Not That Ferroelectric

Abstract

Ice XI, the proton-ordered phase of ordinary ice, features aligned water dipoles. It can be synthesized under laboratory conditions at T ∼ 72 K. Recently, speculations on ice XI in the solar system and the role of its possibly large electric fields in planetary formation have appeared in the literature. We have studied the energetics of ice Ih proton configurations using finite ice slabs and periodic supercell density functional theory (DFT) calculations, while properly taking into account the depolarization field associated with increasing proton order. The depolarization field, not taken into account in previous DFT calculations, dominates the energetics, making the existence of ferroelectric ice unlikely. A single order parameter is shown to describe both the surface dangling-bond configuration and the overall polarization state of the slab. According to our calculations, doping ice with alkali hydroxides or placing it in contact with a metal surface stabilizes a net alignment of water molecule dipoles...