"Similarities" between confined and supercooled water

Abstract

Neutron diffraction and deep inelastic neutron scattering experimentsperformed on bulk stable and supercooled water compared with the sameexperiments performed on water confined in silica substrates.Similarities and differences between the two cases clearly show up, asfar as both microscopic structure and single proton dynamics areconcerned. In particular in both supercooled bulk water and water underconfinement we observe a closer average distance between firstneighbouring oxygen sites and shortening of the H-bonds. In contrastthe number of H-bonds per molecule and the number of interstitial watermolecules are severely reduced under confinement, and the second peakof the oxygen-oxygen radial distribution function is shifted to shorterdistances, compared to the bulk phase. Based on these results apossible scenario for understanding changes evidenced by deed inelasticneutron scattering when water is either confined or supercooled isproposed.