title: The structure of the first coordination shell in liquid water.
abstract: X-ray absorption spectroscopy and x-ray Raman scattering were used to probe the molecular arrangement in the first coordination shell of liquid water. The local structure is characterized by comparison with bulk and surface of ordinary hexagonal ice Ih and with calculated spectra. Most molecules in liquid water are in two hydrogen-bonded configurations with one strong donor and one strong acceptor hydrogen bond in contrast to the four hydrogen-bonded tetrahedral structure in ice. Upon heating from 25 degrees C to 90 degrees C, 5 to 10% of the molecules change from tetrahedral environments to two hydrogen-bonded configurations. Our findings are consistent with neutron and x-ray diffraction data, and combining the results sets a strong limit for possible local structure distributions in liquid water. Serious discrepancies with structures based on current molecular dynamics simulations are observed.
authors.affiliation: Stanford Synchrotron Radiation Laboratory, Post Office Box 20450, Stanford, CA 94309, USA.
authors.forename: Ph
authors.initials: P
authors.lastname: Wernet
authors.forename: D
authors.initials: D
authors.lastname: Nordlund
authors.forename: U
authors.initials: U
authors.lastname: Bergmann
authors.forename: M
authors.initials: M
authors.lastname: Cavalleri
authors.forename: M
authors.initials: M
authors.lastname: Odelius
authors.forename: H
authors.initials: H
authors.lastname: Ogasawara
authors.forename: L A
authors.initials: LA
authors.lastname: Näslund
authors.forename: T K
authors.initials: TK
authors.lastname: Hirsch
authors.forename: L
authors.initials: L
authors.lastname: Ojamäe
authors.forename: P
authors.initials: P
authors.lastname: Glatzel
authors.forename: L G M
authors.initials: LG
authors.lastname: Pettersson
authors.forename: A
authors.initials: A
authors.lastname: Nilsson
mesh_terms: D055598:Chemical Phenomena; D002627:Chemistry, Physical; D003198:Computer Simulation; D006860:Hydrogen Bonding; D007053:Ice; D008956:Models, Chemical; D015394:Molecular Structure; D013057:Spectrum Analysis; D013059:Spectrum Analysis, Raman; D013696:Temperature; D014867:Water / Q000737:chemistry*
chemical_list: D007053:Ice; D014867:Water