Formation and annealing of cubic ice: I. Modelling of stacking faults

Ice Ic, so-called 'cubic ice' (Konig 1943 Z. Kristallogr. 105 279-86), can be obtained, for example, from direct vapour deposition at low temperatures or by warming of recovered high-pressure forms of ice. It is usually obtained in the form of very small crystallites, leading to particle size broadening of the diffraction pattern. This pattern also contains features incompatible with a well-crystallized cubic structure, the details of which depend on the parent phase and the prevailing temperature. We have now corroborated an earlier suggestion (Kuhs et al 1987 J. Physique C1 48 631-6) that an important number of so-called deformation stacking faults exist in cubic ice and propose a model for a quantitative description of stacking faults and anisotropic particle size broadening in ice Ic suitable for profile refinements of its complex diffraction patterns.