Abstract
Ice Ih is a famous crystal which retains residual entropy. The corresponding glass transition exists around 100 K. A 1st-order phase transition observed in ice crystals doped with alkali hydroxides removed a substantial fraction of the residual entropy. A neutron diffraction experiment confirmed an ordered pattern of proton location. The conceptual significance of these experimental findings is discussed in relation to the ordering processes in disordered systems in an equilibrium experiment [J. Cryst. Soc. Jpn. 28, 16 (1986) ] .
