title: The phase diagram of high-pressure superionic ice.
abstract: Superionic ice is a special group of ice phases at high temperature and pressure, which may exist in ice-rich planets and exoplanets. In superionic ice liquid hydrogen coexists with a crystalline oxygen sublattice. At high pressures, the properties of superionic ice are largely unknown. Here we report evidence that from 280 GPa to 1.3 TPa, there are several competing phases within the close-packed oxygen sublattice. At even higher pressure, the close-packed structure of the oxygen sublattice becomes unstable to a new unusual superionic phase in which the oxygen sublattice takes the P2(1)/c symmetry. We also discover that higher pressure phases have lower transition temperatures. The diffusive hydrogen in the P2(1)/c superionic phase shows strong anisotropic behaviour and forms a quasi-two-dimensional liquid. The ionic conductivity changes abruptly in the solid to close-packed superionic phase transition, but continuously in the solid to P2(1)/c superionic phase transition.
authors: Department of Physics, Princeton University, Princeton, New Jersey 08544, USA.
authors: Jiming
authors: J
authors: Sun
authors: Department of Physics, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA.
authors: Bryan K
authors: BK
authors: Clark
authors: Department of Physics, Princeton University, Princeton, New Jersey 08544, USA.|Department of Chemistry, Princeton University, Princeton, New Jersey 08544, USA.|Princeton Institute for the Science and Technology of Materials, Princeton, New Jersey 08544, USA.
authors: Salvatore
authors: S
authors: Torquato
authors: Department of Physics, Princeton University, Princeton, New Jersey 08544, USA.|Department of Chemistry, Princeton University, Princeton, New Jersey 08544, USA.|Princeton Institute for the Science and Technology of Materials, Princeton, New Jersey 08544, USA.
authors: Roberto
authors: R
authors: Car