Ice XI

Ice XI is the proton-ordered form of Ice Ih and was identified in 1972 by Shuji Kawada and others (Ref. 1-3). In principle ice XI forms when ice Ih is cooled to below 72K. It has an orthorhombic structure with the space group Cmc2₁ with eight molecules per unit cell (Ref. 4) Its lattice parameters are a=4.465(3) Å, b=7.859(4) Å, and c=7.292(2) Å at 5 K (Ref. 4).

References

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. 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)
5. Carlos Vega, Carl McBride, Eduardo Sanz and Jose L. F. Abascal "Radial distribution functions and densities for the SPC/E, TIP4P and TIP5P models for liquid water and ices Ih, Ic, II, III, IV, V, VI, VII, VIII, IX, XI and XII", Physical Chemistry Chemical Physics 7 pp. 1450 - 1456 (2005)