A new phase of ice, named ice XV, has been identified and its structure determined by neutron diffraction. Ice XV is the hydrogen-ordered counterpart of ice VI and is thermodynamically stable at temperatures below ~130 K in the 0.8 to 1.5 GPa pressure range. The regions of stability in the medium pressure range of the phase diagram have thus been finally mapped, with only hydrogen-ordered phases stable at 0 K. The ordered ice XV structure is antiferroelectric, in clear disagreement with recent theoretical calculations predicting ferroelectric ordering.
@article{arxiv.0906.2489,
title = {Ice XV: a new thermodynamically stable phase of ice},
author = {Christoph G. Salzmann and Paolo G. Radaelli and Erwin Mayer and John L. Finney},
journal= {arXiv preprint arXiv:0906.2489},
year = {2015}
}