title: Microscopic structure of water at elevated pressures and temperatures.
abstract: We report on the microscopic structure of water at sub- and supercritical conditions studied using X-ray Raman spectroscopy, ab initio molecular dynamics simulations, and density functional theory. Systematic changes in the X-ray Raman spectra with increasing pressure and temperature are observed. Throughout the studied thermodynamic range, the experimental spectra can be interpreted with a structural model obtained from the molecular dynamics simulations. A spatial statistical analysis using Ripley's K-function shows that this model is homogeneous on the nanometer length scale. According to the simulations, distortions of the hydrogen-bond network increase dramatically when temperature and pressure increase to the supercritical regime. In particular, the average number of hydrogen bonds per molecule decreases to ≈ 0.6 at 600 °C and p = 134 MPa.
authors.affiliation: Fakultät Physik/Dortmund Electron Accelerator, Technische Universität Dortmund, Dortmund, Germany. christoph.sahle@helsinki.fi.
authors.forename: Christoph J
authors.initials: CJ
authors.lastname: Sahle
authors.forename: Christian
authors.initials: C
authors.lastname: Sternemann
authors.forename: Christian
authors.initials: C
authors.lastname: Schmidt
authors.forename: Susi
authors.initials: S
authors.lastname: Lehtola
authors.forename: Sandro
authors.initials: S
authors.lastname: Jahn
authors.forename: Laura
authors.initials: L
authors.lastname: Simonelli
authors.forename: Simo
authors.initials: S
authors.lastname: Huotari
authors.forename: Mikko
authors.initials: M
authors.lastname: Hakala
authors.forename: Tuomas
authors.initials: T
authors.lastname: Pylkkänen
authors.forename: Alexander
authors.initials: A
authors.lastname: Nyrow
authors.forename: Kolja
authors.initials: K
authors.lastname: Mende
authors.forename: Metin
authors.initials: M
authors.lastname: Tolan
authors.forename: Keijo
authors.initials: K
authors.lastname: Hämäläinen
authors.forename: Max
authors.initials: M
authors.lastname: Wilke
mesh_terms: D006358:Hot Temperature; D006860:Hydrogen Bonding; D008956:Models, Chemical; D056004:Molecular Dynamics Simulation; D011312:Pressure; D013059:Spectrum Analysis, Raman; D013816:Thermodynamics; D014867:Water / Q000737:chemistry*
chemical_list: D014867:Water