Licentiate: Aspects of the local structure and dynamics of water

by Mr Daniel Schlesinger (Stockholm university)

Wednesday 10 Apr 2013, 14:00 → 16:00 Europe/Stockholm

FB42

In this thesis, we address three different aspects concerning the structure and dynamics of water under ambient and supercooled conditions. In all three projects, the simulations we perform complement experiments and give valuable further insights. In the first project, a new oxygen-oxygen radial distribution function was determined from x- ray diffraction datasets in a careful analysis. We briefly discuss the analysis, particularly the subtraction of the O-H contribution from the structure factor with support from reverse Monte Carlo simulations. The high precision data can be regarded as the current structural standard for ambient liquid water and can serve as a benchmark for force fields used in simulations. The second project deals with the theoretical description of the evaporative cooling process of micrometer- sized water droplets. Droplet injection into vacuum has been used in experiments as a technique to evaporatively cool liquid water down to extremely supercooled conditions and probe its structure before ice nucleation. We review the kinetic theory of evaporation and perform non-equilibrium molecular dynamics simulations for comparison. We then use the theoretical description to estimate the droplet temperature in the experiment. The structure of liquid water at the interface to a BaF2(111) surface is the subject of project number three. Molecular dynamics simulations show a strong layering of water on the surface and a dramatic change of the pair-distribution function of water in the contact layer. The findings support the results obtained from x-ray absorption spectroscopy.