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Ice XI

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Ice XI is the proton-ordered form of Ice Ih and was identified in 1972 by Shuji Kawada (Ref. 1). Other researchers like Takasuke Matsuo and Hiroshi Suga, and Yoshimitsu Tajima also pioneered the study of Ice XI (Ref. 2-3) and were the authors which coined the name "Ice XI" (Ref. 3). In principle ice XI forms when ice Ih is cooled to below 72K. In practice, however, the transition is difficult to produce with pure Ice Ih samples in laboratory timescales. This difficulty is due to the long dielectric relaxation time of ice near the transition temperature, on the order tens of years (Ref. 4), which effectively freezes-in some of the proton-disorder on cooling, even when cooled at slow rates (< -0.1 K/min). Therefore, dopants like KOH are typically used to aid in the transition from Ice Ih to Ice XI by drastically reducing the relaxation time, to the order of milliseconds (Ref. 5), and allowing the transition to rapidly occur. Ice XI has an orthorhombic structure with the space group Cmc21 with eight molecules per unit cell (Ref. 6). Its lattice parameters are a=4.465(3) Å, b=7.859(4) Å, and c=7.292(2) Å at 5 K (Ref. 6).


  1. Shuji Kawada "Dielectric Dispersion and Phase Transition of KOH Doped Ice", Journal of the Physical Society of Japan 32 pp. 1442-1442 (1972)
  2. Yoshimitsu Tajima, Takasuke Matsuo and Hiroshi Suga "Calorimetric study of phase transition in hexagonal ice doped with alkali hydroxides", Journal of Physics and Chemistry of Solids 45 pp. 1135-1144 (1984)
  3. Takasuke Matsuo, Yoshimitsu Tajima and Hiroshi Suga "Calorimetric study of a phase transition in D2O ice Ih doped with KOD: Ice XI", Journal of Physics and Chemistry of Solids 47 pp. 165-173 (1986)
  4. Hiroshi Suga "Frozen-in disorder and slow relaxation in crystals.", The Journal of Chemical Thermodynamics 25 pp. 463-484 (1993)
  5. Syuji Kwada "Acceleration of dielectric relaxation by KOH-doping and phase transition in ice Ih", Journal of Physics and Chemistry of Solids 50 pp. 1177-1184 (1989)
  6. Christina M. B. Line and R. W. Whitworth "A high resolution neutron powder diffraction study of D2O ice XI", Journal of Chemical Physics 104 pp. 10008-10013 (1996)