The structure of ice-I, as determined by x-ray and neutron diffraction analysis

First-principles molecular-dynamics study of surface disordering of the (0001) face of hexagonal ice

“…These peaks correspond to planes of oxygen atoms in layers 1 and 2. Bilayers 2 and 3 are essentially ordered at 190 K. In fact, the full width at half height of 0.3 Å for the four peaks representing bilayers 2 and 3 at 190 K agree with experiment to within less than 0.1 Å: The root-mean-square amplitude of vibration of oxygen in ice at 263 K was measured to be 0.26 Å using x-ray diffraction, 64 while a value of 0.22 Å at 273 K was calculated from thermodynamic data. 65 The two main peaks of bilayer 1 are smeared out more at 230 K and are no longer distinct at 270 K. A smooth transition from order to disorder was also observed by Kroes,26 who showed scrambling of molecules in bilayer 1 of his 12-layer TIP4P ice model at 190 K and complete merging of the two layers at 230 K. In qualitative agreement with our results, Nada and Furukawa observed a continuous transition from disorder to order over a temperature range of 170-220 K in 5 K increments.…”

The Growth, Structure, and Properties of Sea Ice

“…The geometric arrangement of the oxygen atoms, which in the ice structure are the principal diffracting centers for X-rays, is well understood, as ice was one of the first substances to have its structure determined (Bragg 1922, Lonsdale 1958, Owston 1958, Hobbs 1974. The results of these studies are shown in Figure 1.…”

“…In ice discoids this plane of maximum growth is the (0001) or basal plane, which is the plane of maximum reticular atomic density in an ice crystal (Owston 1958). Therefore, ice growth can be said to be well described by Bravais' law: the smaller the reticular density of a crystal surface, the faster it grows normal to itself.…”

Theory of ice structures

“…1(a). It consists of puckered hexagonal layers of water molecules forming hexagonal rings [10]. The four oxygen atoms contained in one unit cell are in crystallographic positions 4/, the tetrahedral coordination of each molecule shifting the oxygen atoms with respect to the average positions of the layers along z in two opposite directions by C/,/16, where Ch is the hexagonal lattice vector.…”