中性子回折実験から見た水素無秩序氷中の水素秩序ドメインの生成と成長

抄録

  Ice exhibits extraordinary polymorphism, with at least 20 experimentally confirmed crystalline phases. This structural diversity arises from the orientational disorder of water molecules governed by the “ice rules,” which impose strict local constraints on hydrogen bonding. Many phases, including ordinary ice Ih, are hydrogen-disordered, while cooling often induces order–disorder transitions leading to hydrogen-ordered counterparts. The transition from a hydrogen-disordered to a hydrogen-ordered ice phase can be regarded as the formation and growth of hydrogen-ordered domains within a hydrogen-disordered structure. The temperature, pressure, and rate of the order–disorder transition depend on the specific ice phase, and the underlying reasons for these differences remain open questions. Here I briefly review our studies on the order–disorder transitions of ice polymorphs—specifically ice VI–XV–XIX and ice VII–VIII—conducted using neutron diffraction methods.