title: Voids in the H-bonded network of water and their manifestation in the structure factor
abstract: The main peak of the oxygen-oxygen structure factor S(OO)(Q) of liquid water shows an unusual doublet structure. The low-Q feature of the doublet shifts appreciably with pressure, between limits which correspond to the position of the first peak in the low- and high-density forms of amorphous ice. This pressure dependence has been cited as evidence of polyamorphism in water. It is shown that this feature is analogous to the "prepeak," or "first-sharp-diffraction peak" which is well known in network-forming ionic liquids, like SiO2, and that its position is determined by the nearest-neighbor separation of voids in the spatial distribution of oxygen atoms.
authors.affiliation: Physical and Theoretical Chemistry Laboratory, Oxford University, South Parks Road, Oxford OX1 3QZ, United Kingdom.
authors.initials: DR
authors.lastname: Barker
authors.initials: M
authors.lastname: Wilson
authors.initials: PA
authors.lastname: Madden
authors.initials: NN
authors.lastname: Medvedev
authors.initials: A
authors.lastname: Geiger