The short-range order in liquid water and amorphous ice

The short-range order in water and ice was determined from experimentally measured partial radial distribution functions by applying the Quasi Crystalline Model (QCM). Partial radial distribution functions were analyzed for water at several pressures and temperatures, crystalline ice, and for the three known phases of amorphous ice: Low-Density Amorphous (LDA), High-Density Amorphous (HDA), and Very-High-Density Amorphous (VHDA). It was found that at low temperatures and pressures, the short-range order of water is similar to that of the hexagonal ice (Ih) structure. At higher pressures and low temperatures, the short-range order of water becomes similar to that of tetragonal ice III structures with a c/a ratio of 0.8. At higher temperatures of 573 K, the short-range order obtained was similar to that of rhombohedral ice II (α = 113°). As for the amorphous ices, we conclude from the QCM analysis that these three forms are structurally distinct with short-range orders corresponding to ice Ih, ice III, and ice II for LDA, HDA, and VHDA ices, respectively.