The nature of the hydrogen-bond network in water and ice is one of the most interesting scientific mysteries, as it is still unsolved and always keenly debated. Professor R. Car (Princeton University, New Jersey, USA) and his colleagues recently published their calculation of the X-ray absorption spectra of water and ice with a many-body approach for electron-hole excitations. Their calculation reproduces some experimental features, including the effects of temperature change in the liquid. The spectral difference between the solid and the liquid has been explained by considering short-range order effects, such as the breaking of hydrogen bonds and a non-bonded molecular fraction in the first coordination shell. For more information, see the paper, "X-Ray Absorption Signatures of the Molecular Environment in Water and Ice", W. Chen et al., Phys. Rev. Lett. 105, 017802 (2010). For more information on the experimental XAFS spectra of water and ice, see the paper, "The Structure of the First Coordination Shell in Liquid Water", Ph. Wernet et al., Science, 304, 995 (2004).
